Wednesday Poster Session & Reception 

5:30 PM – 7:00 PM, Willow

1. Performance Assessment of Seismically Isolated Structures in 2023 Turkey Earthquake
Presenter: Satish Nagarajaiah, Rice University. 
Topic Area: Big Data, Machine Learning, and Artificial Intelligence 

This poster will present the findings of the performance of seismically isolated structures in the earthquake on February 6, 2023, in Turkey. EERI report on the 2023 Turkey earthquake (https://10.18118/G6PM34) describes the observed findings of the EERI team in Table 6.3, on page 264. This Rice University study augments the findings of the EERI team with further data analytics based on computer vision (CV), artificial intelligence (AI), and machine learning (ML) techniques with publicly available photographs and videos on the internet. The Rice team's findings provide further evidence of the effectiveness of seismic isolation in protecting large hospital structures in the 2023 Turkey earthquake as compared with the findings of the senior author, who has studied the USC Hospital base isolated building and Fire Command Control base-isolated building in Northridge earthquake using classical system identification techniques and modern AI, ML and CV techniques in the past three decades. The poster also presents some shortcomings observed in seismically isolated structures in the 2023 Turkey earthquake that resemble those observed in the 1994 Northridge earthquake and in the 2011 Tohoku earthquake in Japan.

2. Geospatial Visualizations of Reconnaissance Data for the 2023 Kahramanmaraş Earthquake Sequence
Presenter: Alejandra Bravo, California Polytechnic State University San Luis Obispo. 
Topic Area: Data Collection and Coordination

The 2023 Kahramanmaras earthquake sequence affecting Turkey and Syria left behind a trail of structural damage. Various organizations participated in data collection post-event, recording structural damage and a range of related metrics. Over 100 buildings were surveyed by members of Degenkolb in Turkey following the 2023 Kahramanmaraş earthquake sequence. This inventory of surveyed buildings included 35 collapsed buildings and 87 buildings with various levels of damage. The reconnaissance team surveyed buildings in various cities including Adana, Antakya, Elbistan, Gaziantep, and Kahramanmaras. This poster depicts the timeline of deployment and data collection, as well as the spatial distribution of the reconnaissance. This poster also presents geospatial and numerical data visualizations that reveal the correlations of structural damage with various parameters. Parameters investigated include peak ground acceleration (PGA), predominant spectral period, building location, liquefaction potential, and building properties including number of stories, occupancy, material, and lateral system. Moreover, this poster explores the influences of geospatial conditions in comparison to the impacts of building properties on structural building damage observed.

3. 6 February 2023 Kahramanmaraş, Türkiye Earthquakes: Lessons Learned from the Reconnaissance
Presenter: Eser Cakti, Bogazici University.
Topic Area: Data Collection and Coordination

We visited the earthquake region within two weeks of the earthquakes as a group of earthquake, civil and geotechnical engineers. The earthquakes affected 11 provinces of Turkey. The rupture extended for over 290 km. The earthquake region covered an area of approximately 110,000 square kilometers. During our stay we were able to carry out observations in the following towns and cities which vary in size and population: Dörtyol, Erzin, Osmaniye, Adana, İskenderun, Antakya, Adıyaman, Kahramanmaraş, Gaziantep, İslahiye, Nurdağı, Arsuz. Our focus was on structural damage to buildings of varying contruction type, age and number of stories, effects on historical structures and heritage, industrial damage, damage to the infrastructure and geotechnical effects. The poster highlights our observations supported by images and provides an ample summary of lessons learned that can be deduced from the destruction caused by the earthquakes.

4. Strong Ground Motion Characteristics of the 6 February 2023 Kahramanmaraş, Turkey Earthquakes
Presenter: Eser Cakti, Bogazici University.
Topic Area: Ground Motions

The earthquakes produced a remarkable strong ground data set recorded by regional stations which are rich in number and well distributed over the affected region. The strong gound motion stations covered the near field quite well. Furthermore they were reasonably distributed over the three segments involved in the rupture. The prominent findings from the analysis of data are as follows: In spite of the unprecedented structural damage, the intensity parameters were within the ranges predicted by the ground motion models suitable for the seismotectonic properties of the region. The near field affects were important and contributed to the damage. The vertical components at some stations are quite high. There are basins in the earthquake affected area such as Antakya basin and Kahramanmaraş basin. The basin response was very significant and well recorded by regional networks. In this poster these forthcoming issues are presented, analyzed and discussed.

5. Rapid Assessment of Ground Shaking and Building Damage Distributions in the immediate aftermath of the M7.7 Kahramanmaraş - Türkiye Earthquake
Presenter: Ufuk Hancilar, Bogazici University.
Topic Area: Emergency Management and Response

In the immediate aftermath of the M7.7 earthquake occurred at 04:17 (local time) on February 6, we worked to assess the spatial distributions of strong ground shaking and number of damaged buildings at the regional scale covering 11 provinces and in the central district of Kahramanmaraş city. Within the first couple of hours of the event, preliminary estimations of the ground shaking intensity and the resulting building damage distributions, which posed a picture of a geographically extended disaster, were obtained and were made available to the research community. In the following days, the ground motion distributions for peak ground acceleration and velocity (PGA and PGV), spectral accelerations (Sa at 0.2s and 1.0s), instrumental intensity (MMI) were re-computed with different prediction models and further improved with the incorporation of recorded strong motion data. Building damage estimations were rectified based on the updated ground motion inputs.

6. Total Collapse of an Elevated RC Water Tank in M7.7 Kahramanmaraş-Türkiye Earthquake (6 Feb 2023)
Presenter: Ufuk Hancilar, Bogazici University.
Topic Area: Lifelines and Utilities

The devastating M7.7 Kahramanmaraş-Türkiye earthquake on Feb 6, 2023 caused extensive and widespread damage not only to buildings but also to lifelines and utilities. A circular shaped, reinforced concrete water container standing on reinforced concrete frame supporting structure totally collapsed in the strong ground shaking. It was located in the backyard of an hospital building that also serves as one of the logistic centers for the National Medical Rescue Team and the basement floor of the building was flooded. This paper presents an investigation of the collapse mechanism of the RC water tank through finite element analysis. The nonlinear dynamic analysis is conducted under the acceleration recording we obtained from the hospital building that is approximately 130 km far from the epicenter.

7. Development Fragility Functions after the Feb.6 2023 Kahramanmaraş - Türkiye Earthquakes
Presenter: Ufuk Hancilar, Bogazici University.
Topic Area: Structural Engineering

The Feb. 6, 2023 Kahramanmaraş-Türkiye earthquakes affected 11 provinces with more than 14 million inhabitants in total and caused over 53,000 deaths and financial losses exceeding 100 billion U.S. Dollars. The Ministry of Environment, Urbanization, and Climate Change of the Republic of Türkiye conducted extensive field based damage assessment in the affected areas and surveyed over 1.7 million buildings, which have more than 5 million dwelling units. According to the official reports, total number of collapsed, very heavily damaged buildings (the buildings that tagged as ‘to be urgently demolished’) and heavily damaged buildings reach over 262k. This study presents the fragility functions developed based on the damage data collected in the Kahramanmaraş city center. The fragility functions were derived for different damage states and in terms of two ground motion intensity measures (i.e. PGA and PGV).

8. Liquefaction Ground Deformations and Cascading Coastal Flood Hazard in the 2023 Kahramanmaraş Earthquake Sequence
Presenter: Patrick Bassal, The Ohio State University. 
Topic Area: Geotechnical Engineering

The 2023 Kahramanmaraş earthquake sequence produced extensive liquefaction-induced ground deformations and ongoing flooding along the shoreline of the Mediterranean port city of İskenderun, Türkiye. Historic insights, field observations, available field data, and remote sensing analyses are used to investigate whether earthquake-induced liquefaction was a significant factor for increasing the flood hazard in İskenderun. Geotechnical reconnaissance observations following the earthquakes included seaward lateral spreading, settlement beneath buildings, and failures of coastal infrastructure. Lateral spreading case histories indicate consistent ground deformation patterns with areas of reclaimed land. Persistent Scatterer Interferometry (PSI) measurements from Synthetic Aperture Radar (SAR) imagery identify a noticeably greater rate of pre- and post-earthquake subsidence within the İskenderun coastal and urban areas relative to surrounding regions. The PSI measurements also indicate subsidence rates accelerated following the earthquakes and were typically highest near observed liquefaction manifestations. These evaluations suggest that while the liquefaction of coastal reclaimed fill caused significant ground deformations in the shoreline area, ongoing subsidence of İskenderun and other factors likely also exacerbated the flood hazard. This study provides an overview of these observations and findings in İskenderun to suggest the importance of evaluating liquefaction and cascading flood consequences for enhancing the resilience of coastal cities in high seismicity areas.

9. Rapid Seismic Multi-impact Assessment for 2023 Kahramanmaraş Earthquake Using Near-Real-time Information Retrieval and AI-based Information Fusion
Presenter: Susu Xu, Johns Hopkins University.
Topic Area: Emergency Management and Response

Rapid loss assessments needed for rapid response and aid in hard-hit cities, such as Hatay, Adiyaman, and Kahramanmaras in the 2023 Kahramanmaraş Earthquake, were hampered by challenging travel, a lack of on-the-ground resources, and the immense scope of the disaster. Satellite imagery and drones were of limited availability and varying quality and thus required expert interpretation. Conversely, the rapid, empirically-based models for estimating casualties and building damage are highly uncertain with additional complications due to strong aftershocks. What makes these estimations more complicated and challenging are that in addition to shaking-induced damage, secondary hazards, such as liquefaction and landslides contributed further to building damage, roadblocks, communication network outage, and population displacement. Furthermore, all these factors change dynamically with time as aftershocks incur more damage and population displacement. Tracking how the concentrations of losses change over time is critical for understanding the evolving nature of the disaster, essential information needed for responders and aid agencies, and overall situational awareness. In this poster, we will present how we can take advantage of near-real-time disaster information for guiding rapid disaster response in this earthquake. We developed methods and tools that effectively utilize easy-to-access data (e.g., remote sensing data and crowdsourced data) for large-scale near-real-time disaster multi-impact assessments. The impacts of interest include (1) infrastructure damage, (2) human mobility, and (3) human casualties. More specifically, we provide spatial estimates of building damage probability, communication network outages, evolving reports of casualties in Turkey and Syria, as well as how population density and human movement changed after the devastation. The information may help government and aid agencies as well as first responders better plan their rescuing and recovering activities, and provide research communities with high-quality data to better understand how disaster impacts evolve and how people respond in finer-grained temporal resolution.

10. Insights into Seismic Energy Spectra Analysis: A Study of the 2023 Kahramanmaraş Earthquake and Aftershocks
Presenter: Tomas Nunez, UBC. 
Topic Area: Ground Motions

Based on the records obtained from the 2023 Kahramanmaraş earthquake in Turkey (M_w=7.8) and its main aftershock (M_w=6.6) followed by a second earthquake (M_w=7.7), the following study aims to present the results obtained from the processing of seismic records in terms of energy spectra. It highlights that while using energy spectra is not as widely known as response spectra, it can provide insights into information that may help establish a correlation with observed damage. The study presents results in spectral terms for input energy, dissipated energy considering viscous damping, and plastic energy, using a bilinear, 5% hardening model, accounting for the effect generated by aftershocks and the second event. Quantitatively, including aftershocks into the analysis leads to an increase in plastic energy of approximately 10-20% compared to considering solely the main event.

11. Lateral Spreading Observations in Dӧrtyol, Hatay Following the 2023 M7.8 Pazarcık Turkiye Earthquake
Presenter: Kristin Ulmer, Southwest Research Institute.
Topic Area: Geotechnical Engineering

Following the February 6th, 2023, M7.8 and M7.6 Pazarcık and Kahramanmaraş Turkiye earthquakes, the Geotechnical Extreme Event Reconnaissance (GEER) organization worked with local universities and organizations to dispatch multiple teams to the area to gather data related to geotechnical failures such as liquefaction-induced settlement, lateral spreading, foundation damage, and other ground failures. Our team surveyed areas in and around Gӧlbaşı, Pazarcık, Dӧrtyol, Ӏskenderun, and Türkoğlu from February 28 – March 4, 2023. This poster presents our observations of a network of lateral spread cracks and soil ejecta in Dӧrtyol and includes a discussion of the regional geology and ground motions recorded nearby.

12. Generating Empirical Damage and Liquefaction Fragility Functions from Post-event Reconnaissance: A Case Study using the 2023 Earthquake Sequence in Kahramanmaraş, Turkey
Presenter: Christina Sanon, Tufts University. 
Topic Area: Multidisciplinary 

Fragility curves are an efficient tool for risk assessment that can help quantify the probability of different levels of damage or failure given a seismic intensity. Liquefaction susceptibility is a critical factor influencing the seismic vulnerability of structures and combining this information with ground shaking intensity enhances the accuracy of fragility assessments. Following the recent earthquake sequence beginning on February 6, 2023, in Kahramanmaraş, Turkey, an estimated population of 14.01 million people across 11 provinces were affected primarily because of structural failure and damage. Our research endeavors to convert reconnaissance data into actionable knowledge. We are proposing a novel approach for developing fragility functions by integrating liquefaction probability maps that offer spatial distribution of liquefaction potential with Peak Ground Acceleration (PGA) data as a proxy for ground shaking intensity. Using an empirical approach to capture the as-built conditions for building construction in modern-day Turkey, the methodology presented leverages data from various reconnaissance reports, including GEER, StEER, and UNOSAT building damage from the recent 2023 earthquakes in Turkey to update fragility functions for residential buildings. The resulting functions can be subsequently used for evidence-based decision-making, enabling authorities to allocate resources efficiently for public policy, urban planning, and infrastructure development, and to prioritize mitigation measures. Moreover, the methodology holds applicability in regions with similar existing data, extending its utility beyond the immediate context.

13. Advancing Disaster Response: Lessons Learned from the AFAD- The 6 February 2023 Earthquakes Clearinghouse in Türkiye
Presenter:  Recep Cakir, ndependent Researcher. 
Topic Area: Post-earthquake emergency response/planning 

The catastrophic Mw7.7 and Mw7.6 earthquakes that struck eastern Türkiye on February 6, 2023, prompted the rapid establishment of an earthquake clearinghouse by the Disaster and Emergency Management Agency of Türkiye (AFAD), facilitating the collection and management of perishable data and coordination efforts. TUBITAK (The Scientific and Technological Research Council of Türkiye) coordinated approximately 500 researchers from universities across Türkiye to manage the reconnaissance data flow from the disaster area and joined the AFAD-Clearinghouse team. Additionally, the clearinghouse served international reconnaissance teams such as EERI-GEER reconnaissance teams from the US, as well as other teams from Europe, Asia, and South America. Utilizing a variety of reconnaissance forms from established EERI libraries and customized based on team requests, comprehensive perishable data of ground deformation and damaged structures were collected. Integration of remote sensing technologies, such as damage proxy maps from the Earth Observatory of Singapore, further tested to enhance reconnaissance efforts, particularly in identifying landslide and rockfall occurrences. The rapid establishment and effective operation of the national earthquake clearinghouse by the AFAD team marked a significant milestone for Türkiye. Building upon this success, the tools and practices implemented during the February 6th, 2023 earthquakes will be refined and applied in future large earthquakes. The database generated by the clearinghouse will serve as a valuable resource for stakeholders, providing insights into critical structural and building damages, soil seismic behaviors and other site effects, and fault surface ruptures, thereby aiding in better preparedness and response strategies for future earthquakes in Türkiye.

14. ASCE/COPRI Earthquake Field Reconnaissance
Presenter: Dolunay Oniz, Simpson Gumpertz & Heger Inc.
Topic Area: Recovery

In the aftermath of the 2023 earthquakes in Turkey, marine infrastructure and facilities emerged as crucial assets in the rescue and recovery efforts. Along the Gulf of Iskenderun, ports, fisheries, and waterfront facilities played pivotal roles by facilitating transportation for rescue teams, distributing aid to survivors, and offering temporary housing and schooling through lifeships. Thus, ensuring the accessibility and functionality of these facilities was imperative for an effective and swift recovery process. This presentation encapsulates the insights and assessments conducted by the Earthquake Field Reconnaissance team of the American Society of Civil Engineers/Coasts, Oceans, Ports & Rivers Institute (ASCE/COPRI) during May 2023. The team surveyed 15 public and private facilities spanning from Mersin to Arsuz along the coastal region to evaluate the damage inflicted on marine infrastructure and to understand the earthquake's impact on these structures. The examined structures encompassed pile-supported structures, gravity and sheetpile quaywalls, gravity breakwaters, bridges, and near-shore buildings. While pile-supported structures exhibited minor to no damage, necessitating a short recovery period, gravity structures sustained moderate damage, leading to operational disruptions and requiring a more extensive repair process. Notable observations included significant lateral spreading in gravity quaywalls, whereas sheetpile quaywalls remained unaffected. Near-shore structures with shallow foundations and gravity breakwaters experienced liquefaction and substantial vertical settlement. Even structures with minimal or no structural damage encountered operational setbacks and unexpected downtime due to damages to conveyor systems, critical firewater lines, and rail cranes. Rapid response efforts were pivotal in facilitating operational recovery by providing immediate assistance to facility personnel and offering temporary housing solutions.

15. Women's labor force participation in the 2023 Kahramanmaraş earthquake-stricken region: The case of Nurdağı, Gaziantep
Presenter: Anne Wein, U.S. Geological Survey (USGS).
Topic Area: Social Science

Continuing economic functionality is a prerequisite for urban, community, and household recovery after disasters. Facilitating the return of employees to work will help accelerate the post-disaster recovery of households and their communities. Of particular interest are women employees who have unique challenges with the work-life balance. The aim of this study is to reveal the difficulties and expectations of women residing in the region directly affected by the February 6th, 2023 Kahramanmaraş Earthquakes in participating in the labor market in the post-disaster period. In doing so, the town of Nurdagi in Gaziantep, where the effects of the February 6th Earthquakes can be clearly observed, was chosen as the case study. A face-to-face survey was conducted with 375 women residing in the container city of Nurdagi on the one-year anniversary of the earthquake. The survey questions focused on family, housing, and job losses due to the earthquake suffered by the women of the region in their households and workplaces, their migration status after the earthquake, the problems in their participation in the labor market, and their expectations. In the one-year period after the earthquake, the most predominant problem is living conditions, and the predominant need is permanent housing. Other obstacles to women's participation in the workforce, the difficulties encountered, and their needs were revealed as psychological support and care for children or elderly. Although temporary work programs provided by the state support women's employment, among those surveyed, they have largely served previously unemployed and only 13% of previously employed women. Forty-five percent of previously employed women remain unemployed after the earthquakes. Thus, many women are needing a regular income-generating and permanent job. In the face of widespread damage, having a safe living environment and workplace accessibility has become the most basic need.

16. Performance of non-structural elements in isolated hospitals during the 2023 Kahramanmaraş Earthquakes
Presenter: Edgar Tapia-Hernández, Universidad Autónoma Metropolitana - Azcapotzalco. 
Topic Area: Structural Engineering

This research is based on a post-earthquake inspection conducted in the field, seven weeks after the earthquakes. The focus was on hospitals in the affected region, including government, private, and university hospitals. When possible, interviews were conducted with hospital management and staff members to understand key decisions and potential rehabilitation activities after the earthquake. In the area affected, twelve hospitals were seismically isolated. The hospitals could function adequately and provide emergency response operations despite the severe damage reported in the region. No structural damages were reported, even in the hospitals nearest the fault. The performance of these hospitals was in contrast to those that were not seismically isolated. However, some non-structural elements were damaged.  In several cases, non-structural elements and facilities were damaged due to the insulated structure not being correctly separated from the non-insulated structure. Critical functionality components and non-structural damage in isolated hospitals are discussed in detail. It emphasizes addressing non-structural damage and conceptual deficiencies that can compromise medical functionality. Detailed discussions on various instances of damage in infill walls that lacked resilience, improper connections of pipes, ceiling panels, stairs, access ramps, and adhered cladding around elevators, among others, are provided. The spectral acceleration, velocity, and displacement data from the nearest accelerometric stations to the isolated hospitals are included. The acquired experience and knowledge would improve construction details in other isolated hospitals or buildings to maintain continuity of service and retrieve applicable lessons. Additionally, it aims to comprehend the key decisions made before and during the earthquakes and how they adjusted their operations to ensure the continuity of service, despite the damage in non-structural components.

17. On the responses of four neighboring buildings in Antakya during the 2023 Kahramanmaras Earthquakes: engineering insights from reconnaissance and simulations
Presenter: Fatih Canakci, Purdue University.
Topic Area: Structural Engineering  

Following the 2023 Kahramanmaras Earthquakes, engineering teams supported by Committee 133 of the American Concrete Institute (ACI) surveyed close to 300 buildings in the disaster zone. A residential complex, comprising four recently built reinforced concrete buildings, in Antakya provided a unique opportunity and challenge to engineers to study. All four buildings had identical plans and structural configuration. While one of the buildings was 8-story, the others were 13. The final state of the buildings was the key element in the puzzle: one of the 13-story building was found to have total collapse; another one was found to have lost its ground story; the third 13-story building had very large permanent deformations, as if frozen in time, with nearly 6% drift ratio measured in its ground story. The 8-story building had sustained damage in its core walls but did not have permanent offset or elevation loss. In this study, the behavior of these four buildings have been studied using different engineering and numerical tools, and the followings are presented: observed structural damages; application of a simplified seismic vulnerability assessment tool, known as the Hassan index as measured by the cross-sectional areas of columns and shear walls relative to the total floor area; review of the recorded ground motions and their comparison with design level parameters specified per the online & location based 2018 Turkiye Seismic Hazard Map prepared by Disaster and Emergency Management Authority of Turkiye (AFAD); 3D modal and time-history analysis of the 13-story building, the one with permanent drift, using finite element model (FEM) of the structure based on its layout and measured dimensions of its structural elements obtained during the reconnaissance.

18. Performance of Concrete Bridges in the 2023 Kahramanmaraş Earthquake Sequence: Field Investigations and Numerical Analyses
Presenter: Jeffrey Hunt, Exponent. 
Topic Area: Structural Engineering

The 2023 Kahramanmaraş Earthquake sequence resulted in extensive destruction of the built environment across Turkiye and Syria. Although more than 160,000 buildings collapsed or were severely damaged, the bridge infrastructure demonstrated surprisingly adequate performance given the severity of the shaking with few reported collapses. Two of the authors performed post-earthquake reconnaissance of 98 bridges across the affected regions in Turkiye to document damages to substructure and superstructure components. While many bridges exhibited generally good performance, there were several examples of unexpected damage patterns to some of the bridges, including damage to precast concrete girders, failure of shear keys at bent caps, rubber bearing pad dislodgement, and residual drift of abutments and piers. Most of the severely damaged bridges exhibited thick/flexible bearing pads, insufficient or missing shear keys, and absence of deck-to-girder diaphragm elements. A 3D bridge numerical model of the Hatay Stadium Bridge, an archetypical bridge with observed aforementioned damages, was developed to investigate the influence of shear keys, bearings, and diaphragms on its overall performance during the 2023 Kahramanmaraş Earthquake sequence. A parametric study with nonlinear dynamic analyses were conducted using the recorded ground motions at a nearby recorded station for the Mw 7.8 main event and Mw 6.4 aftershock, in series. The bearing pad thickness, inclusion of a deck-girder diaphragm, and strength of the shear key blocks all have significant impact on the performance and repairability of concrete bridges following strong earthquakes.

19. The structural damage observed during 2023 Kahramanmaraş Earthquakes in historical buildings and its relationship to ground motion characteristics
Presenter: Mohsen Zaker Esteghamati, Utah State University. 
Topic Area: Structural Engineering

On February 6, 2023, the East Anatolia region of Turkey was struck by two consecutive earthquakes separated by a 9-hour interval, causing extensive damage and loss of lives. According to the USGS, the epicenters were in Pazarcık and Elbistan, with reported moment magnitudes of Mw=7.8 and Mw=7.5, respectively. The East Anatolia region affected by the earthquake, including Adana, Adıyaman, Kahramanmaraş, Gaziantep, Şanlıurfa, Diyarbakır, Osmaniye, Hatay, Kilis, Malatya and Elazığ, has a large number of cultural heritage primarily composed of masonry structures. This study aims to present the structural damage and failure patterns induced by the Kahramanmaraş Earthquake sequences to historical masonry structures over the affected region. Particular attention is given to the distribution of strong motion characteristics and construction techniques that affected the seismic performance of these historic structures. To this end, a field reconnaissance has been conducted to evaluate the structural aspects of the Kahramanmaraş Earthquake sequences based on observations, including unreinforced and timber-reinforced masonry structures. In addition, the causes of structural failures, encompassing local, in-plane, out-of-plane, and combined mechanisms, are documented.

20. Seismic Performance Assessment of Cast-in-Place Tunnel-form Concrete Buildings
Presenter: Reza Filizadeh, Simpson Gumpertz & Heger, Inc.
Topic Area: Structural Engineering 

The tunnel-form system stands out for its remarkable seismic capacity, achieved through integrated structural elements, rapid construction, cost efficiency, and enhanced quality and safety for workers. These features have made the tunnel-form system one of the most popular options for mass construction using industrial methodologies, justifying its application in construction sites with any seismic hazard level. Reconnaissance Field assessments conducted following earthquakes in Turkey (1999 and 2023) strongly support the acceptable seismic performance of tunnel-form buildings among different reinforced concrete systems. Despite the widespread adoption of tunnel-form construction techniques, it has not been credited as an independent structural system in the existing seismic codes, resulting in limited familiarity among researchers and designers. This study aims to introduce the tunnel-form system and evaluate its seismic behavior. The results obtained from pushover and fragility analyses of 5 and 10-story models demonstrate the high seismic capacity of the tunnel-form structural system. Considering local damage criteria in wall and coupling beam elements, the models exhibited a performance level higher than Immediate Occupancy (IO) under design basis earthquake (DBE) and maximum considered earthquake (MCE) scenarios, with a return period of 475 and 2475 years, respectively. Based on these observations, the structure models are expected to withstand even higher earthquake intensities. Therefore, the use of cast-in-place tunnel-form is recommended for high seismic zones.

21. Comparison of Measured and Estimated Seismic Settlements of Buildings and Surroundings at the Coastal Areas of Iskenderun in 2023 Kahramanmaras Earthquakes
Presenter: Ozgun Alp Numanoglu, Schnabel Engineering.
Topic Area: Geotechnical Engineering

February 6th, 2023, Kahramanmaras earthquake sequence induced significant damages in the southern and south-eastern part of Turkiye. Two subsequent reconnaissance campaigns led by the authors revealed that the City of Iskenderun, a coastal district of Hatay, experienced seismic-induced liquefaction and foundation damage which resulted in the total collapse of several buildings. Furthermore, widespread partial damage in terms of seismic-induced settlements and tilting of the buildings were observed. The authors interpreted and documented observations on the settlement and tilting for several buildings. Subsequently, a combination of different simplified semi-empirical models was used to calculate the seismic-induced settlements and the results were compared. To do this, ground motion intensity measures (IMs) including the peak ground acceleration (PGA), pseudo-spectral accelerations (PSA), and the standardized cumulative absolute velocity (CAVdp), were estimated at the building sites using Kriging interpolation and spatial correlation models developed using Bayesian inference. These IMs were then used in estimation of seismic settlement. The comparison of the measured and estimated results shows that the proposed simplified semi-empirical models provide a rational approach for first order estimate of the seismic settlements. Furthermore, building- and site-specific dynamic time history analysis is warranted to consider further complexities.

22. Strategies for Enhancing Industrial Resilience After the 2023 Kahramanmaras, Turkey Earthquakes
Presenter: Zeynep Tuna Deger
Topic Area: Structural Engineering

The earthquakes on February 6th, 2023, with moment magnitudes of 7.8 and 7.5 have devastated southeast Turkey, affecting more than 11 cities. Field reconnaissance revealed that the disaster not only affected urban areas but also resulted in substantial damage to industrial zones, causing economic losses and hindered the region's recovery, given its strong dependence on local industries. The majority of industrial facilities in the region that have suffered damage or collapse were constructed using prefabricated structures designed and implemented in accordance with older seismic regulations. The observed damages extend beyond the structural systems of such buildings – substantial damage and losses are caused due to the failure of non-structural components, including cladding, machinery, and equipment. This has caused noteworthy interruptions in both the production process and the supply chain. Within the scope of this paper, the most commonly observed damages in industrial facilities and their underlying causes are discussed. Some easy-to-implement suggestions are provided to enhance the seismic performance of the most widespread type of existing industrial buildings and a showcase retrofit project of an industrial building that implements proposed retrofitting methods is demonstrated. Additionally, some of the ongoing or recently completed innovative retrofitting methods such as damper retrofit for industrial buildings in Turkey is presented.

23. Surrogate Models of Highway Bridges for Regional-Scale Simulations of Transportation Networks
Presenter: Mia Lochhead, Stanford University.
Topic Area: Big Data, Machine Learning, and Artificial Intelligence

Understanding the performance of a regional bridge stock is an integral part of planning for the design, retrofit, and post-earthquake recovery of transportation systems. This research focuses on the development and implementation of high-fidelity simulations of bridge performance using two machine learning methods, Probabilistic Learning on Manifolds (PLoM) and a Gaussian Process (GP) model. Each of the surrogate models is trained to estimate the bridge response based on a set of specific structural and ground motion parameters. The two models are trained using nonlinear response analyses of archetype bridge designs under a gridded set of ground motion parameters. The models are validated by assessing the performance of 36 archetype bridges distributed around the San Francisco Bay Area under ground motions corresponding to the HayWired M7 Earthquake Scenario, simulated using the SimCenter’s R2D application software with an API to the USGS UCERF/OpenSHA server. The 36 archetype bridges are selected to assess bridges with different locations, distances to the fault, Vs30 values, structural characteristics, and design eras. At each bridge site, spatially-correlated ground motions are selected and run through OpenSees models corresponding to specific bridge designs to generate a “ground truth” dataset. The two surrogate models are then assessed using the same ground motion and structural input data as was passed into the OpenSees model. Validation is done by directly comparing the bridge response parameters from the OpenSees models to those predicted by the PLoM and GP models. After generating response parameters using the OpenSees, PLoM, and GP models, results are passed into Caltrans fragility functions in order to evaluate the performance of the models in predicting damage and loss in the bridge structures. This study compares the accuracy of the predictions from each model, as well as ease of use, dimensionality, input and output distribution capabilities, and limitations of the models.

24. Rapid Map: A mechanics-informed machine learning model for regional liquefaction hazard planning and response
Presenter: Morgan Sanger, University of Washington.
Topic Area: Big Data, Machine Learning, and Artificial Intelligence

Site-specific soil liquefaction analyses are a critical component of any infrastructure project in seismic regions. For many owners, agencies, and stakeholders, there is a need to extend beyond the site boundaries of single assets and consider the liquefaction hazards affecting entire communities or infrastructure networks (e.g., transportation and pipeline systems). Ideally, these predictions could be made quickly, in near-real-time after an event, and at high resolution, consistent with the scale of individual assets. Towards this end, this project uses a novel combination of machine learning (ML) methods with geospatial data, in-situ testing, and established liquefaction mechanics to predict the probability of liquefaction manifestation at map-scale. The model is developed using available cone penetration tests (CPTs), where the probability of ground failure is computed for each CPT across a range of peak ground accelerations (PGAs) using CPT-based mechanistic models. The modelled relationship of liquefaction hazard with PGA becomes the ML target variable at each CPT location. Then, a suite of publicly available geospatial proxies of liquefaction are identified (e.g., geology maps, depth bedrock maps, etc.), which are sampled at each CPT location and become the ML predictor variables. The ML model is trained to identify the relationships between the predictor variables and targets, such that it can be applied in the forward direction to predict the liquefaction hazard across an entire mapped area. The final product is a map tool which – given an input ground-motion (PGAM7.5) raster – estimates probabilities of liquefaction manifestation in seconds, at high resolution, across a mapped extent of interest. This exciting and practical application of mechanics-informed ML extends the existing liquefaction hazard knowledge beyond site specific analyses to inform regional hazard planning, mitigation, response, and recovery.

25. Understanding Basin Effects and the Impact on Structural Response and Damage through Causal Lens
Presenter: Rashid Shams, University of Southern California (USC). 
Topic Area: Big Data, Machine Learning, and Artificial Intelligence

Earthquakes pose a significant threat to the life safety and well-being of a large portion of the world’s population. Moreover, as the rate of urbanization exceeds the rate of population growth, so will the risks that are associated with seismic hazards. The effects of sedimentary basins on infrastructure damage have been observed in numerous earthquakes that have occurred in the past few of decades. The state-of-the-art in assessing the effects of sedimentary basins in ground shaking and infrastructure damage is rooted in traditional statistical methods and assumptions regarding geomorphological homogeneity. Specifically, quantifying the effect of sedimentary basins on ground shaking intensity and duration is currently addressed using ergodic procedures, which employ a median derived from the site response component of the Next Generation Attenuation-West2 (NGA-W2) ground motion models. Similar to the GMMs (Ground Motion Models), the infrastructure response and damage studies have also approached the problem through a statistical lens and only attempt to compare basin versus non-basin effects. Because they adopt a statistical approach, the challenge of having multiple confounding variables (many of which are correlated) is not rigorously addressed in these studies. We take an interdisciplinary approach to quantifying the effect of basin geomorphology on ground shaking, infrastructure response, and damage where the problem is addressed through the lens of causal inference. We use causal machine learning to isolate the effect of multiple geomorphological features (individually and collectively) on ground shaking, and then estimate the causal relationship to structural response and damage. This will allow for a direct quantification of the impact from basin amplification on seismic performance. This work represents a potential paradigm shift where drawing insights from earthquake and infrastructure data moves “beyond statistics” to more explicit consideration of cause and effect.

26. Nonlinear Behavior of Reinforced Concrete Columns with Shear Degradation Under Seismic Loading up to Collapse
Presenter: Sasan Dolati, University of Texas at San Antonio. 
Topic Area: Building Codes and Building Performance

Concrete columns are considered critical elements with respect to the stability of buildings during earthquakes. Post-earthquake evidence shows that shear failure in non-ductile detailed columns is a major source of structural collapse and earthquake deaths. While experimental investigations of concrete columns subjected to seismic loading have been conducted over the last few decades, gaps still remain in the range of parameters that have been investigated, particularly when it comes to loading history. Nonlinear continuum finite element (FE) models were constructed and calibrated to experimental tests for nine columns sustaining shear and axial degradation during cyclic loading. The primary objective of this study was to develop FE guidelines for simulating the lateral cyclic behavior of concrete columns sustaining shear degradation and axial collapse, such that wider parametric studies can be conducted numerically to improve the accuracy of assessment methodologies for such critical columns. Selected columns covered a practical range of axial loads, shear stresses, transverse reinforcement ratios, longitudinal reinforcement ratios, and shear span-to-depth ratios. The crack width, the damage in concrete and reinforcement, the drift at axial and lateral collapse, and the shear capacity of columns are compared with experimental results and standards equations from ASCE 41-17 and the ACI 318-19. It is observed that material model parameters recommended in this study deliver relatively high accuracy for columns with span-to-depth ratios above 2 up to the axial collapse, and for columns with span-to-depth ratios below 1 up to the lateral failure, while the percent error for the drift at axial failure is significantly higher for these columns.

27. Response Modification of Moment Resisting Frames using Rocking Wall
Presenter: Mehrdad Aghagholizadeh, Loyola Marymount University.
Topic Area: Building Codes and Building Performance

The high occupancy levels in urban multistory buildings, in association with current safety considerations inevitably leads to a reconsideration of performance objectives. In view of the appreciable seismic damage and several weak-story failures (some at mid-height) of multistory buildings that have been documented after major earthquakes, there has been a growing effort to develop an alternative hybrid structural system that are not only resilient but also satisfy requirements of being sustainable design. This paper investigates the inelastic response of a yielding structure coupled with different configurations of rocking walls. The paper first derives the nonlinear equations of motion of a yielding oscillator coupled with a rocking wall.  Then, the dependability of the one-degree of freedom idealization is validated against the nonlinear time-history response analysis of a multistory moment-resisting frame that is coupled with a stepping rocking wall. The SDOF idealization presented in this paper compares satisfactory with finite‐element analysis of a multi‐story building coupled with a stepping rocking wall; therefore, the SDOF idealization can be used with confidence for preliminary analysis and design. The planar response analysis of this paper concludes that for medium‐rise to high‐rise buildings, vertical tendons in rocking walls are not beneficial. Additionally, in most cases, use of dampers is effective way of reducing maximum deformation in the coupled system; while the additional lever arm for the dampers appears to have marginal effect on the peak response, in particular for taller walls.

28. Evaluation of Two-Stage Analysis and Design Provisions for Multi-Story Buildings
Presenter: Morgan McBain, Stanford University. 
Topic Area: Building Codes and Building Performance

The seismic design provisions of ASCE 7-16 and ASCE 7-22 Section 12.2.3.2 permit a two-stage analysis procedure for building structures meeting certain criteria. The procedure is intended for the design of “structures that have a flexible upper portion above a rigid lower portion” and, thus, is often used for the design of multi-story wood or cold-formed steel framed buildings on stiff concrete podium structures. This project evaluates the criteria presented in ASCE 7-16 and ASCE 7-22 for use of the two-stage analysis procedure including 1) the lower portion must be at least 10 times stiffer than the upper portion, and 2) the period of the full structure cannot be greater than 1.1 times the period of the upper portion analyzed independently to ensure conservativeness in design. The prescriptive seismic design criteria are evaluated through nonlinear response history analyses of a multi-story wood frame building as both a standalone structure and on a concrete podium structure. Analysis of four models with varying stiffness and period ratios leads to the conclusion that the ASCE 7 criteria may not be stringent enough to ensure conservativeness in calculation of story drift demands.

29. Assessment of Plan Irregularity Limits in the New Zealand Standard - NZS 1170.5
Presenter: Uzochukwu Uwaoma, University of Washington. 
Topic Area: Building Codes and Building Performance

Buildings with plan irregularities are susceptible to increased damage levels under seismic excitation. This is due to the amplification and concentration of demands on certain structural members stemming from torsional modes of response. NZS 1170.5 specifies a limit on the torsional irregularity allowed in buildings to mitigate these effects. However, there are no additional restrictions or guidelines on acceptable global response of the structure. This is in contrast with other specifications, such as the American and Canadian building codes, which provide system restrictions and acceptable global structural response based on the magnitude of seismic hazard. Considering these differences, this research is focused on quantifying the effectiveness of NZS 1170.5 in dealing with plan-irregular buildings relative to other international standards. The first phase of this work consisted of a comprehensive literature review that summarized the irregularity requirements from a significant number of international guidelines. The current phase of the work consists of a comparative study that will assess the seismic performance of two selected case study buildings ‑  one with a reinforced concrete shear wall lateral force resisting system and the other with special steel moment frames - modeled to capture various levels of plan irregularities while accounting for the response thresholds and system restrictions in several international building codes. These case study buildings are representative of current design practices in New Zealand and will be modeled using nonlinear numerical techniques. The case study buildings will be subjected to spectrally matched, hazard-consistent ground motions scaled to varying site-specific intensities. The results from this study will provide quantitative data that will be used to update the plan irregularity specifications in New Zealand.

30. Seismic Structural Assessments for Buildings Exposed to a Corrosive Environment
Presenter: Alexandra Saccente, Oregon State University. 
Topic Area: Climate, Multi-hazard Modeling, and Earthquake Resilience

Corrosion is one of the major causes of structural deterioration for steel structures. For steel structures, corrosion deterioration can lead to material degradation, resulting in a reduction of material strength and stiffness properties and ultimate failure of the structure. Current assessment of corroded steel is highly variable and often leads to inaccurate evaluation of the structure’s condition. To overcome these limitations, a quantitative assessment methodology was developed using remote scanning techniques coupled with finite element method (FEM) modelling. In this study, the methodology was applied to a two-story corroded steel-framed structure located on a historical industrial site. The geometric information and cross-sectional properties of the structure were obtained from lidar point cloud data, which were then used for FEM analysis to evaluate the residual seismic behavior of the building. In addition, the impact of corrosion on the seismic performance of a steel-frame building was quantified through 1st mode period, seismic base shear, and inter-story drifts. The results of the analysis indicate an increase in 1st mode period and inter-story drifts, and a decrease in seismic base shear.

31. Climate Change Amplification of Earthquake Risk to Communities
Presenter: Heidi Stenner, GeoHazards International. 
Topic Area: Climate, Multi-hazard Modeling, and Earthquake Resilience

Climate change can amplify communities’ risks from earthquakes in a number of ways. The amplified risks of most significance from earthquake shaking are an increase in landslides, avalanches, and liquefaction, in locations where rainfall totals are increasing or rain events are becoming more extreme. With the increased landslides and avalanches, and rising global temperatures increasing glacier, snow, and permafrost melt, there is a growing risk from flooding due to landslide dams, landslides entering lakes, and glacial lake outburst floods. Rising global temperatures are increasing the risk from earthquake-triggered wildfire. Tsunami inundation can increase where sea level is rising or where groundwater tables are rising from increasing precipitation and extreme rain events. Compound events, such as a strong earthquake occurring close in time with a tropical storm or cyclone, will also be amplified from climate change’s effects on temperature and rainfall, and these effects can be further amplified as tropical cyclones increase in severity. These initial findings are from a four-year Amplified Risk program currently being led by GeoHazards International (GHI), a non-profit committed to saving lives by empowering at-risk communities worldwide to build resilience ahead of disasters and climate impacts. The program, funded by the United States Agency for International Development (USAID), aims to increase collective understanding of how earthquake and volcanic hazards, and their societal impacts, may be affected by climate change in at-risk low- and middle-income countries. The program will also identify potential ways to reduce climate change-amplified earthquake and volcanic risks to people and society. For practical implementation, the team will take steps to reduce local risks by collaborating with a community in the Philippines and in two other yet-to-be-specified locations. The program team will offer program findings and risk reduction guidance to a variety of stakeholders and leaders of interested at-risk communities.

32. A Framework for Probabilistic Assessment of Liquefaction Manifestation
Presenter: Kenneth Stewart Hudson, UCLA.
Topic Area: Geotechnical Engineering

As part of the Next Generation Liquefaction (NGL) project, we are developing probabilistic triggering and manifestation models using laboratory data and case histories in the NGL database. The case histories are used to develop probabilistic models for surface manifestation conditional on susceptibility, liquefaction triggering, soil properties, stratigraphic details, and other features. Susceptibility is interpreted as a sole function of soil composition and is expressed as a probabilistic function of soil behavior type index, I_c, obtained from cone penetration testing (CPT). A triggering model is derived based on laboratory tests on high-quality specimens from literature; this model captures mean responses and uncertainty reflective of data dispersion and is considered as a Bayesian prior that will subsequently be updated by field observation data. A manifestation model is then regressed from field case histories where surface manifestation was or was not observed, information on soil conditions that enables identification of layers likely to liquefy, and ground shaking conditions. We describe the approach applied to develop our manifestation model; for a given layer this model considers layer depth, thickness, CPT tip resistance, and I_c. The result of this process is a combination of logistic functions in which manifestation probability decreases with increasing depth, decreasing thickness, increasing tip resistance, and increasing I_c. Profile manifestation is then derived by aggregating individual layer manifestation probabilities.

33. Public Health Extreme Events Research (PHEER) Network: A Collaborative, Multi-Institutional Approach to Conducting Time-Sensitive Public Health Disaster Research
Presenter: Katelin Teigen, University of Washington, School of Public Health.
Topic Area: Other

As public health emergencies continue to become more frequent and complex, evidence is needed to guide public health preparedness, response, and recovery programs. A 2020 National Academies of Science, Engineering and Medicine study declared that “the science underlying the nation’s response to public health emergencies is seriously deficient, which hampers the nation’s ability to effectively respond to emergencies, save lives, and preserve well-being.” The study concluded that collaboration, infrastructure and resources are needed to establish and sustain a public health disaster science community of practice. In response, the CDC funded the development of the Public Health Extreme Events Research (PHEER) Network in 2022, through an interagency agreement with the NSF. PHEER is a researcher- led network that aims to advance the public health disaster science field by coordinating a community of practice that can rapidly mobilize to conduct time-sensitive research in the aftermath of disasters. PHEER is one of eight extreme events reconnaissance or research (“EER”) communities that comprise the broader NSF-funded CONVERGE network. The EER ecosystem brings together geotechnical engineering, interdisciplinary research, nearshore research, operations and systems engineering, public health, social sciences, structural engineering, and sustainable material management networks to encourage cross-disciplinary data collection, information sharing, and collaboration. The goal of this EER system is to inform policies and decision-making that can reduce harm from disasters and strengthen community resilience. In its first year, PHEER has established a community of practice, governance structure, and Concept of Operation (CONOPS) for mobilization. In its second year of funding, PHEER is piloting a virtual mobilization in response to the Maui Wildfire event in order to develop a process for identifying, collecting, sharing, and analyzing data after a disaster. This Maui pilot will also inform a potential PHEER field operations response and to serve as a template for future mobilization efforts.

34. Predicting Bridge Performance Via Seismic Scenarios: A Direct Displacement-Based Assessment Approach
Presenter: Ana Paula Bona Barros Medeiros, North Carolina State University. 
Topic Area: Post-earthquake emergency response/planning

After a seismic event, bridges hold the potential to function as critical lifeline structures by providing an alternative path for emergency evacuation. Consequently, the ability to forecast the seismic performance of these structures allows for the strategic planning of disaster response and the reduction of potential losses. In recent years, a range of assessment tools, such as HAZUS by FEMA, have been employed to anticipate and assess the extent of hazard consequences through seismic scenarios simulations. However, two primary constraints are notable within the context of these tools. First, they often hinge on ground motion intensity measure parameters based on acceleration. However, it is widely accepted that the correlation between acceleration and structural damage is inadequate, with spectral displacement being recognized as a more robust and reliable intensity measure. The second limitation relates to the high-level nature of the assessment offered by existing tools. This is due to the limited structural data employed to derive the system’s capacity curve, which precludes the execution of a thorough assessment. With the intention to address these limitations, the Direct Displacement-Based Assessment (DDBA) approach was deployed to predict the performance of four fictitious multi-span bridges under different earthquake scenarios. The seismic scenarios considered were Cascadia subduction zone earthquake events. The findings of this work will contribute to the development of reliable tools for emergency response planning and training based on realistic seismic scenarios.

35. Developing and Implementing an International Macroseismic Scale (IMS) for Earthquake Engineering, Earthquake Science, and Rapid Damage Assessment
Presenter: David Wald, U.S. Geological Survey. 
Topic Area: Post-earthquake emergency response/planning

Macroseismology plays a crucial role in earthquake hazard and risk analyses, tying earthquake occurrences and impacts from the past with those of the present and future. Nonetheless, even with best practices, there are key limitations to many modern macroseismic data collection approaches. For example, the United States and New Zealand still employ variations of the Modified Mercalli Intensity (MMI) scale, consistent with—but inferior to—the more recently developed 1998 European Macroseismic Scale (EMS-98). Practitioners in many other countries outside of Europe deploy EMS-98 informally, and often, so do researchers working there. We report on the efforts to finally develop an International Macroseismic Scale (IMS), building on the impressive EMS-98 framework. We motivate the IMS, noting its seismological and earthquake engineering benefits and summarize the historical efforts leading to this global scale. We then describe key features of the IMS, its consistency, and differences with respect to the EMS-98 framework, including additional structures in an expanded building vulnerability table. Moreover, the IMS will allow for national annexes that document crucial structural characteristics, code era, compliance considerations, and other potential vulnerability modifiers endemic to buildings in that specific region that will help narrow vulnerability class assignments. Lastly, a sizeable ongoing effort entails developing and promoting more uniform, pre-earthquake exposure and vulnerability class data collection and post-earthquake building damage characterization consistent with the requirements of the IMS (i.e., building classes, damage grades, and damage percentages). We will facilitate uniform damage data collection by employing relatable building taxonomies and enhancements to existing inspection and reconnaissance protocols; these conventions, too, will be described in each nation’s building annex. Consistent, concerted damage data collection efforts will allow for immediate IMS assignments and contribute directly to better earthquake engineering damage and geotechnical forensics, vulnerability model development, and many other earthquake hazard, loss, and risk analyses.

36. Advancing Seismic Resilience: Updating CSMIP Buildings
Presenter: Facundo Sirri
Topic Area: Post-earthquake emergency response/planning

California has one of the highest levels of earthquake risk in the US. Besides life loss, 1971 San Fernando M_w 6.6 earthquake inflicted more than half a billion dollars in damage, making it apparent there was, at the time, a general lack of understanding of exactly how ground motion impacted structures. This led the California Geological Survey (CGS) to develop the California Strong Motion Instrumentation Program (CSMIP), whose mission would be to provide seismologists, engineers, building officials, and emergency response personnel with the data critical to the development of building code and policy that would minimize damage and enhance emergency response for future seismic events. The timely investment in this program led to a wealth of strong motion data during 1994 Northridge Earthquake, which produced some of the highest-ever accelerations at structures and ground response sites and highlighted the shortcomings of the existing ground motion attenuation models predictions. The program resulted in the development of key building design parameters and codified designing structures to withstand larger seismic forces. Since its inception half a century ago, 70% of the equipment dispersed throughout California has become obsolete due to ever-evolving technology. Due to significant gaps in the infrastructure for receiving, processing, interpreting, archiving, and disseminating strong motion data, the state, through an instrumentation update project, intends to further its commitment to seismic resilience by once again partnering with Kinemetrics, a world leader in earthquake monitoring technology, to provide modern instrumentation for over 900 stations including complete overhaul of over 70 strategically selected critical structures. The $20M+ project, which is set to run through 2026, is poised to ensure the continuation and expansion of the vital research, seismic provisions, and policy initiated in the 70’s by addressing current deficiencies and providing professionals and institutions with updated, more accurate data to advance seismic resilience.

37. Improving situational awareness and decision-making: Unifying real-time earthquake business continuity and earthquake early warning
Presenter: M. Khalid Saifullah, Kinemetrics Inc.
Topic Area: Post-earthquake emergency response/planning

Historical earthquakes, whether the 1994 Northridge or the 2024 Noto Peninsula Earthquake, illuminate the significance of informed decision-making, which is critical to streamlining recovery and planning efforts. Uninformed decision-making after any earthquake increases the potential for panic and injuries and puts lives at risk. While already distressed and, unfortunately, with little or no real information at hand, emergency responders and building managers must make dozens of real-time decisions to ensure safety, immediate response, and continued business operations. Any misjudgment or misallocation of resources at this critical time can lead to severe negative impacts in the form of social and economic losses. Fortunately, advancements in seismic monitoring technology and performance-based earthquake engineering have paved the way for platforms like OasisPlus from Kinemetrics. This platform enables responders to rapidly reach well-informed decisions through real-time data from sensors that is integrated with information such as hazard reports, occupant check-ins, safety checks, etc., and presented in the management console in a simple, comprehensible, and effective manner. Realizing the importance of the precious seconds just before the shaking starts, the platform has been recently augmented with the capability to integrate information from state-of-the-art Earthquake Early Warning (EEW) systems. Although any local/regional early warning system can also be leveraged, Kinemetrics has entered into a License to Operate agreement with USGS to distribute ShakeAlert® integration within OasisPlus after a substantial testing and review process. This functionality has enabled extension of the event trigger timeline into the preimpact phase, prior to the onset of the detection of building shaking by the sensors. The platform is designed to minimize the overall system latency to maximize the amount of pre-event alert time available to the end-user. Testing has demonstrated that, on average, end-users receive alerts within 400.6 milliseconds of the publishing of an event by ShakeAlert®.

38. Exploring Basin Amplification Within the Reno, Nevada and Wellington, New Zealand Metropolitan Areas with Non-Ergodic Physics-Based 3D Scenarios
Presenter: John N. Louie, Terēan and the University of Nevada, Reno. 
Topic Area: Seismology and Earth Science

The Reno, Nevada and Wellington, New Zealand metropolitan areas are both subject to significant seismic risks, exacerbated by the urban areas’ presence within thin (< 1 km thick) sedimentary basins. Instrumental recordings of shaking from M6+ quakes close to Reno do not exist, although the 2008 M5.0 Mogul quake produced recorded accelerations well over 1g. During the 2016 7.8 magnitude Kaikōura earthquake, the Wellington capital region experienced unexpectedly localized zones of damage due to focused seismic energy within its sedimentary basin. To help explore these hazards, we used SW4, a physics-based wave-equation modeling tool, to compute a suite of non-ergodic scenarios at low frequency (up to 1.0 Hz). Comparisons between SW4 peak ground velocity (PGV) computations, and PGV estimates calculated from empirical ground-motion models as well as physics-based models having no basins emphasize the degree to which even very thin basins may result in greater hazards than are currently predicted. Non-ergodic scenario computations for small earthquakes in and around the two cities suggest basin amplifications commonly exceed a factor of four between 0.3 and 1.0 Hz. These amplifications develop despite the thickness of low-velocity sediments below Reno and Wellington rarely exceeding 1 km. Ergodic PGV maps show apparently chaotic patterns of basin-related focusing, trapping, and edge effects at 0.3-0.9 Hz. Non-ergodic averages across the ergodic single-event PGV maps are simpler, appearing to show correlation between basin depths and the averaged PGV. The standard deviation of these averages appears to highlight basin edges. Fourier spectral ratios of distance-corrected horizontal shaking spectra of basin over rock stations also show large ergodic variations across the quakes modeled for each city. Taking a non-ergodic average of the log spectral ratios across all the modeled quakes reveals much simpler basin amplification spectra. The non-ergodic basin amplification spectra may be predictable from empirical GMPEs.

39. The physical basis for the source term in the non-ergodic ground motion model
Presenter: Shiying Nie
Topic Area: Seismology and Earth Science

The Ground Motion Prediction Equation (GMPE) is a fundamental tool used to estimate the intensity of ground shaking in seismic hazard assessment. While traditional ergodic GMPEs provide stable ground motion models, they are burdened with significant aleatory uncertainty that cannot be mitigated through more data acquisition. This limitation has spurred the pursuit of non-ergodic models, which consider to decompose aleatory uncertainties to site-, source-, and path-specific epistemic uncertainties. Among those non-ergodic terms, the source term has presented a challenge due to the absence of a rigorous physical explanation. In this study, we propose to connect the source term with dynamic stress drop. To support our investigation, we employ a dataset containing records of 5297 earthquakes in the San Francisco Bay area from 2002 to 2016, spanning a magnitude range of M1-4. This dataset provides both calibrated stress drops for these earthquakes and peak ground accelerations (PGAs). In our approach, we develop a non-ergodic ground motion model (GMM) using a gaussian process regression (GPR) method. GPR is a widely accepted technique for constructing non-ergodic ground motion models that can effectively account for the spatial variability of source, path, and site-specific characteristics. Likewise, we also establish a non-ergodic stress drop model, which incorporates a spatially variable mean stress-drop term. Our findings reveal a strong correlation between the source term of the non-ergodic GMM and the non-ergodic stress drop term. In a small area, their correlations are even stronger. This suggests that dynamic stress drop is a crucial factor in shaping the source-related component of ground motion model. Moreover, our results indicate the potential for further adjustments to the median ground motion within the traditional ergodic model by incorporating the stress drop database.

40. A study on solitary-wave-structure interaction using hydro real-time hybrid simulation
Presenter: Akiri Seki, Stanford University. 
Topic Area: Structural Engineering

In seismic regions, structures offshore and along the coast may be exposed to earthquake and tsunami loading during their service life. During the 2011 Great East Japan earthquake, many structures survived the earthquake but failed due to the subsequent tsunami loading. This research aims to generate data about the effects of tsunami waves on coastal structures, however, conventional approaches have limitations when simulating structures interacting with hydrodynamics. Computational methods require experimental validation, but scaled experimental methods may not represent full-scale prototype response because of the unique similitude law governing the hydrodynamics versus the structural dynamics. Real-time hybrid simulation (RTHS) can alleviate the similitude limitations by partitioning the system subjected to structural- and hydro-dynamics into physical and numerical sub-assemblies. The sub-assemblies interact through actuators and sensors in real time, which enables the application of individually applied similitude laws to each sub-assembly. Here, physical solitary waves and a rigid cylindrical specimen were coupled with a numerical single degree-of-freedom (SDOF) system via RTHS. In the NHERI Large Wave Flume at Oregon State University,  breaking and broken solitary waves were excited to the physical specimen, whose natural period was then numerically manipulated. Results showed the effect of wave-structure interaction depends on the duration of the wave loading and natural period of the SDOF system.

41. Seismic Bridge Design: Exploring Ground Motion Directionality and Bidirectional Response
Presenter: Ariadne Palma Parra, North Carolina State University. 
Topic Area: Structural Engineering

In bridge design, analyses are traditionally conducted separately in the two orthogonal principal directions of the structure, namely longitudinal and transverse directions. However, it is recognized that bridges experience multidirectional demands during earthquakes, which may not align with the principal axes of the structure. To account for this multidirectional characteristic, seismic analysis has incorporated directionality measures on both hazard and structural response calculations. From the hazard perspective, response spectra incorporate directionality by considering all possible directions in defining the ground motion representation. At the same time, seismic design codes provide criteria for combining the structural response, such as the 100% - 30% combination rule in US codes, which has remained unchanged for decades. Engineers often interchange these two concepts and assume both account for the same effect, which is not the case. For example, using the 100% - 30% combination rule is not sufficient on its own to account for the directionality effect. This study evaluates how current design codes account for earthquake directionality in representing the earthquake hazard and structural response. To achieve this, a bridge model was designed using Direct Displacement-Based Design for two response spectra definitions, RotD50 and RotD100. The resulting bridge designs were evaluated using simplified methods as well as nonlinear time history analysis to assess the adequacy of existing combination rules and hazard definitions. This study will help inform whether the current code approaches to directionality are adequate or should be modified.

42. High-Performance Steel-Timber Composite Rocking Shear-Wall System for the Next Generation of Tall Mass Timber Buildings: Preliminary Seismic Study for Acceptability
Presenter: Christopher Leong, The University of British Columbia. 
Topic Area: Structural Engineering

Efforts to reduce global warming, particularly in structural and earthquake engineering, have led to a surge in environmentally positive design solutions. With growing populations and decrease in available land, tall mass timber buildings are a logical and rational solution to meet the demands of the future.  A feasibility study of a novel seismic force-resisting steel-timber composite rocking shear wall system of balloon-type construction is presented. The system utilizes cross-laminated timber (CLT) and standard steel plates in a CLT-steel-CLT section to achieve composite action. Replaceable Resilient Slip Friction Joint (RSFJ) dampers at the base of the wall dissipate energy during rocking motion while the rest of the wall remains damage-free. The composite panels are connected using grout-reinforced steel rod connections, mimicking rigid connection behaviour while ensuring a continuous load path, modularity, and ease of construction. The system is benchmarked using a fictitious 15-story building located in Vancouver, BC, Canada. The seismic forces are calculated using standard code procedures and finite-element analysis in ANSYS is performed to determine the optimal composite section configuration. A series of non-linear seismic analysis is carried out in OpenSees using selected crustal, subcrustal, and subduction ground motions according to NBCC 2020 guidelines. A push-over analysis is also performed to verify the ductility and capacity of the composite shear wall system before the activation of the damping system. System performance exceeded NBCC 2020 drift requirements and FEMA P-695 acceptable collapse margin ratios. The RSFJ dampers at the base of the wall successfully dissipated energy and the remainder of the wall stayed within the linear-elastic range, thus allowing the system to be reused after replacement of the dampers.

43. Column Axial Forces in Tall Reinforced Concrete Buildings Under Horizontal and Vertical Ground Motions
Presenter: Connie I. Chen, Exponent. Topic Area: Structural Engineering

Tall buildings are of special interest when considering the combined effects of horizontal and vertical earthquake ground motions because of the high axial loads commonly carried by columns. Among tall reinforced concrete buildings, a common configuration consists of a centrally located core wall surrounded by flat plates and perimeter columns. Under lateral loads, the slab-column gravity framing acts as an outrigger for the core walls, causing an increase in the axial forces in the columns due to the overturning moment resistance provided by the gravity system. The vertical fundamental period of a reinforced concrete tall building is likely to coincide with the short-period amplification range of vertical ground motions, which may result in increased column axial forces. This study examined the column axial forces in a tall core-wall building under the combined effects of vertical ground motions and outrigger action of the gravity system under horizontal ground motions. An archetypal core-wall building with 40 stories was designed for this study, and a nonlinear finite element model was developed to represent a slice from the building plan. Nonlinear response history analysis was performed using a suite of ground motion records at the MCE_R-level with both the horizontal and vertical components of ground motion, with varying source-to-site distances and magnitudes. The results of this study show the relative contributions of horizontal and vertical ground motions on the axial forces in a perimeter column of the archetype building.

44. 3D Scanning Corroded Reinforcing Steel
Presenter: David Comaniciu, North Carolina State University. 
Topic Area: Structural Engineering

In high seismic areas, assessing damage in reinforced concrete structures is paramount for structural safety. The widespread issue of steel corrosion in concrete structures leads to mechanical property degradation and heightened susceptibility to seismic events, necessitating precise evaluation methods. 3D scanning offers a non-destructive way of assessing the extent of damage caused by corrosion, a well conditions like cracks and spalling. The collected data can enable the quantification of remaining strength and estimation of the structure's service life. Moreover, advanced computational techniques like finite element analysis and machine learning can be integrated to predict structural behavior under seismic loads. The potential advantages of this technology include improved safety, reduced maintenance costs, and enhanced disaster preparedness in earthquake-prone areas.

Thursday Poster Session & Reception 

5:30 PM – 7:00 PM, Willow

1. Building a Neural Network to predict Seismic Resilience of Concrete Box-Girder Bridges: A model-free approach
Presenter: Jacob Atkins, Oregon State University.
Topic Area: Big Data, Machine Learning, and Artificial Intelligence 

The growing emphasis on resilience in engineering, driven by environmental concerns and economic factors, has led to increased attention on the use of Machine Learning in structural analysis and design. Machine Learning (ML) methods have been around since the late 1950s, and gone through periods of both growth and stagnation while being applied to a litany of different problems in various fields. One of the contemporary applications of ML techniques is in the creation of resiliency models for structural analysis and design. ML algorithms hold significant potential for improving the accuracy and speed of predictive modeling. This potential is particularly vital in assessing the resilience of highway bridges, which play a critical role in ensuring efficient transportation and communication, especially in high seismic regions. The ML model can be used to increase the efficiency of resource allocation to retrofitting such bridges, or as a basis for further analysis. This project presents an innovative approach, leveraging Artificial Neural Networks (ANN), to model the seismic resilience of box-girder concrete highway bridges. Our primary objective is to conduct a comparative analysis, pitting ANN-based predictive seismic modeling methods against traditional regression and other common ML approaches. Through this research, we aim to shed light on the effectiveness and potential benefits of employing ML within the realm of structural analysis and design, thereby contributing to the evolution of engineering practices in the face of ever-growing resiliency demands.

2. ML Driven Terrain Unit Analysis
Presenter: Jessica Feenstra, WSP USA Inc.
Topic Area: Big Data, Machine Learning, and Artificial Intelligence

Terrain unit analysis is used in remote areas with little to no geotechnical or geological information to inform infrastructure design. This technique leverages available geospatial data and available geotechnical or geological data to interpret the surficial geology and anticipated conditions within the upper 20 to 30 feet of the subsurface. Terrain unit analysis is a time and labor-intensive process that involves interpreting and hand digitizing each terrain unit boundary based on observed surface features. Over the last 10 years, we have developed terrain unit maps spanning thousands of square miles across northern and interior Alaska, including a wide variety of permafrost terrain. In this paper, we leverage our extensive database of terrain unit data to train a convolutional neural network (CNN) to classify terrain units based on input geospatial images. Our training data is developed by extracting tiles of images clipped to each terrain unit, labeled with the centroid and corresponding terrain unit. We identify the performance of satellite imagery versus hillshade images from LiDAR, including various methods of shading in training the model. The CNN model incorporates transfer learning from vetted CNN architectures to boost model performance. Our trained CNN model is then used to classify tiles of imagery data extracted from unmapped areas of northern Alaska. Grouping analyses are performed on the centroids of the classified image tiles to aggregate the points into terrain unit polygons for these unmapped portions of Alaska. The automation of terrain unit mapping is a novel development in this field that will allow terrain unit maps to be accessible to a wider variety of infrastructure projects.

3. Data Driven Machine Learning Model to Predict Shear Wave Velocity of Coastal Sediments
Presenter: John Thornley, WSP USA Inc. 
Topic Area: Big Data, Machine Learning, and Artificial Intelligence 

Estimating Vs from cone penetration testing (CPT) data is of interest due to the widespread use and suitability of CPT for the characterization of coastal sediments. The application of machine learning (ML) algorithms in geotechnical engineering has received increased attention recently which brings the possibility of discovering new insights into how CPT data and Vs are correlated. The performance of models developed using ML at sites where no field data was available at the time of the prediction has not been widely tested. In this paper, the performance of an ML model developed for all soil types is evaluated using datasets from two seismic CPTs conducted on the coast of Alaska. The performance of the ML model is compared to the field-measured Vs and other widely used empirical correlations. The results show that the ML model outperformed the empirical correlations when applied to natural silt and sand materials. It did not perform as well when applied to coastal clays. The application of the ML model was partly successful. The “success” opens the possibility of using the ML model to estimate the shear wave velocity of offshore sediments without the need for expensive field testing. On the other hand, the “failure” of this approach indicates the difficulties in developing a truly “universal” model. Soil behavior index from CPT data may not be sufficient to characterize all soil types, especially for silt-sized materials that tend to exhibit clay-like behavior during cone penetration but sand-like behavior at rates of dissipation. A dataset of natural clays was added to the original dataset used to train the ML model. The updated model was then applied to the site and the site-specific performance of the model was improved. Results are discussed, and practical recommendations are made for predicting site-specific shear wave velocity using ML algorithms.

4. Machine Learning for Regression Analysis in Shake Table Data
Presenter: Kayla Erler, University of California San Deigo.
Topic Area: Big Data, Machine Learning, and Artificial Intelligence

The Seismic Response Modification Device (SRMD) test facility is essentially a high-capacity shake table, typically used for testing seismic protection devices such as seismic isolation bearings and dampers. An empirical model was initially developed to fit testing results of machine inherent forces; however, it was found to be inaccurate for small acceleration amplitude tests. Machine learning based algorithms are developed using regression analysis techniques to accurately model the inherent forces starting from a physics-based model. Relatively large data exists for model development with respect to many structural engineering applications. For complex nonlinear regression analysis of time series data, methods such as linear regression are well known for providing simple and interpretable results. These models require well-formulated relationships that may be difficult to fit or limited in the level of accuracy achievable. Questions addressed in the process of fitting these models relate to both model interpretability and validity of training data with small signal-to-noise ratios. Preliminary results show a feed forward neural network can provide significantly increased performance over the initially implemented traditional model. While this model provides enhanced improvement, some questions remain regarding the potential for increased reliability that may be achievable upon further architecture and loss modifications; however, results do not indicate that the machine learning model provides less reliability than that of an empirically derived relationship. An additional objective of this work was to provide developed codes readily accessible through the DesignSafe cyber infrastructure that is part of the NSF-funded Natural Hazard Engineering Research Infrastructure. The developed neural network training algorithm has been designed for ease of reconfiguration to alternative datasets with automated tuning features. Commentary exists in these projects on the process of model development and the trade-off between model accuracy and interpretability.

5. Enhancing Critical Information Integration to Reinforced Concrete Building Databases through Advanced Pose Detection Techniques
Presenter: Lissette Iturburu, Lyles School of Civil Engineering, Purdue University.
Topic Area: Big Data, Machine Learning, and Artificial Intelligence 

The automated identification of building characteristics for seismic vulnerability remains a challenge when developing building databases due to the sheer volume of buildings in urban areas. The diverse architectural styles of these buildings complicate the automated identification of building information. Deep learning techniques lose accuracy as they generalize information while the visual contents of a building exhibit a considerable range and diversity. To tackle such issues, this study leverages the pose detection technique on a common construction style: reinforced concrete buildings representing columns, beams, or floors on the façade. With an aim to enable the assessment of seismic vulnerability, the technique developed herein is conceived for buildings with up to six stories that are more likely to be moment-frame buildings. The main outcomes of this study are (1) the identification a framework that can streamline the automated detection of building frames, (2) the determination of critical elements for the implementation of this method in buildings such as the per-keypoint constant and, (3) the development of guidelines for data collection.

6. Characterization of the construction period of buildings in Beirut using multi-modal machine learning
Presenter: Mayssa Dabaghi, American University of Beirut.
Topic Area: Big Data, Machine Learning, and Artificial Intelligence

Multiple efforts have contributed to collecting data on the built environment in Beirut. However, these efforts usually rely on time-consuming and labor-intensive field visits that are prone to human errors. Such data are crucial to perform seismic risk and vulnerability assessments on a city scale. This work uses artificial intelligence practices for automated characterization of building construction period, which is related to expected structural performance. The proposed framework is applied to Beirut, where five construction periods are identified and used: pre1935, 1935-1955, 1956-1971, 1972-1990, and post1990. Data consisting of street-view images, construction period, number of floors, and location of buildings in Beirut is compiled from various sources. Three approaches for predicting construction period are explored: (1) the novel transformer-based Swin-T model with an input street-view image; (2) a fully connected neural network model with input tabular data that include the number of floors and socio-economic background of the building; and (3) a late fusion of the Swin-T model and fully connected neural network, thus using both types of inputs. The three approaches were trained on the same dataset and their overall accuracy on the test set was 72.74%, 60.53%, and 78%, respectively. The multi-modality model achieved the best performance and higher confidence in the predictions. It is used in a toy example to predict the construction period of buildings in a Beirut neighborhood and assess its vulnerability to an earthquake scenario. The earthquake consequences are simulated using the Regional Resilience Determination (R2D) tool developed by the NHERI SimCenter. The R2D tool requires as input a description of the earthquake scenario of interest and data on the built environment (the location, plan area, number of stories, year built, occupancy class, structure type, and replacement cost per square meter of each building), and outputs for each building the estimated damage and losses.

7. Near-real-time Earthquake-induced Fatality Estimation using Crowdsourced Data and  Large-Language Models
Presenter: Susu Xu, Johns Hopkins University.
Topic Area: Big Data, Machine Learning, and Artificial Intelligence 

When a damaging earthquake occurs, immediate information about casualties (e.g., fatalities and injuries) is critical for time-sensitive decision-making by emergency response and aid agencies in the first hours and days. Systems such as Prompt Assessment of Global Earthquakes for Response (PAGER) by the U.S. Geological Survey (USGS) were developed to provide a forecast of such impacts within about 30 minutes of any significant earthquake globally. However, existing disaster-induced human loss estimation systems often rely on early casualty reports manually retrieved from global traditional media, which are labor-intensive, time-consuming, and have significant time latencies. Recent approaches use keyword matching and topic modeling to identify human casualty-relevant information from social media, but tend to be error-prone when dealing with complex semantics in multi-lingual text data, and parsing dynamically changing and conflicting human death and injury number shared by various unvetted sources in social media platforms.  In this work, we introduce an end-to-end framework to significantly improve the timeliness and accuracy of global earthquake-induced human loss forecasting using multi-lingual, crowdsourced social media. Our framework integrates (1) a hierarchical casualty extraction model built upon large language models, prompt design, and few-shot learning to retrieve quantitative human loss claims from social media, (2) a physical constraint-aware, dynamic-truth discovery model that discovers the truthful human loss from massive noisy and potentially conflicting human loss claims, and (3) a Bayesian updating loss projection model that dynamically updates the final loss estimation using discovered truths. We test the framework in real-time on a series of global earthquake events in 2021 and 2022 and show that our framework effectively automates the retrieval of casualty information faster but with comparable accuracy to those now retrieved manually by the USGS.

8. A novel probabilistic residual drift model that yields more realistic predictions of irreparable damage in building performance assessments
Presenter: Adam Zsarnoczay, Stanford University. 
Topic Area: Building Codes and Building Performance

In this work, we introduce an end-to-end framework to significantly improve the timeliness and accuracy of global earthquake-induced human loss forecasting using multi-lingual, crowdsourced social media. Our framework integrates (1) a hierarchical casualty extraction model built upon large language models, prompt design, and few-shot learning to retrieve quantitative human loss claims from social media, (2) a physical constraint-aware, dynamic-truth discovery model that discovers the truthful human loss from massive noisy and potentially conflicting human loss claims, and (3) a Bayesian updating loss projection model that dynamically updates the final loss estimation using discovered truths. We test the framework in real-time on a series of global earthquake events in 2021 and 2022 and show that our framework effectively automates the retrieval of casualty information faster but with comparable accuracy to those now retrieved manually by the USGS. In modern, code-conforming buildings, the potential replacement of the entire building due to irreparable damage is often one of the most significant contributors to seismic risk. The permanent horizontal displacement of each floor is typically used to characterize the likelihood of experiencing irreparable damages. Such displacements are quantified by the residual interstory drift ratios along the height of the building. These quantities are challenging to approximate in a reliable manner with idealized empirical formulas. However, obtaining a sufficiently large sample from high-fidelity numerical analysis is not feasible either, especially in engineering practice. Hence, FEMA P-58, the current state of the art in seismic performance assessment, recommends fitting a probabilistic lognormal model to the small sample from numerical analysis and re-sampling that model to generate a large enough dataset for damage and loss assessment. This study proposes a new probabilistic model for residual drifts. The distribution of residual drifts typically does not follow a lognormal distribution, especially at small intensities where the likelihood of having no permanent deformations (i.e., zero residual drift due to elastic response) is non-negligible. Our model substantially improves the characterization of residual drifts by using a Weibull distribution that is conditioned on peak interstory drift values. The efficacy of this model is evaluated using the results of 5760 dynamic analyses of 18 archetypes of steel braced and moment frames. A case study with more than 1000 simulated residual drifts for a single building illustrates that our model yields a more realistic residual drift sample and reduces the bias in loss estimates compared to the conventional approach recommended in FEMA P-58. The proposed residual drift model will be available in the open-source Pelicun library to broadly support risk assessments both in engineering practice and academic research.

9. Behavior of Braced Frames with Elastic Spines
Presenter: Bryam Astudillo and Barbara Simpson, Stanford University. 
Topic Area: Building Codes and Building Performance

Recent advancements in seismic hazard mitigation and resilience have led to exploring and developing lateral-force resisting systems with enhanced performance goals. In this context, the Strongback Braced Frame (SBF) offers a more uniform drift distribution with building height and can better utilize the energy dissipation capacity of the chosen energy dissipators (e.g., Buckling Restrained Braces, BRB) by introducing an elastic spine (i.e., the strongback). However, properly sizing the spine, along with selecting and placing the energy dissipators, remains challenging and lacking standardized procedures due to 1) the kinematic and force compatibility between the pivoting spine and the energy dissipators and 2) the near-elastic higher modes that are present in this type of system; both closely governed by the selection of the spine strength and stiffness. This study investigates the response of strongback braced frames to develop a standardized design of the system. Eight-story archetypes are considered with variations in strongback implementation, such as embedding it into the main frame or keeping it separate. The results include the behavior of different archetypes, highlight the demands for sizing energy dissipators and elastic components of the spine, and underscore the near-elastic higher-mode demands arising from the inclusion of the spine. It is expected that results from this paper may inform future code-based provisions to adopt the use of near-elastic spines in enhanced performance systems such as the SBF.

10. Loading History Effects on Drift Capacity of Reinforced Concrete Columns Under Seismic Loading
Presenter: Sasan Dolati, Stantec. 
Topic Area: Building Codes and Building Performance

Experimental studies have indicated that the lateral and axial behaviors of concrete columns under seismic excitation can be highly dependent on loading history, particularly at high-damage states. However, most experiments on concrete columns have used fully reversed cyclic loading protocols, with only limited tests in the literature exploring the effects of loading history. Due to the lack of experimental data, continuum finite element models were constructed to cover a relatively wide range of column parameters and failure modes, with primary objective of quantifying the effects of loading history on both lateral and axial degradation of concrete columns. Eighteen column models representing experimentally tested columns were subjected to varying lateral loading protocols, including different axial load levels. A total of 116 simulations were conducted to axial failure. The effects of the lateral loading protocols on strength and deformation capacities of concrete columns were quantified. Relations for estimating reductions in drift capacities due to increased lateral cycling are proposed for both initiation of lateral strength degradation and initiation of axial degradation.

11. Seismic Performance of Discontinuous RC Shear Walls in TOC Overbuilds Designed Following Provisions in NBCC 2020
Presenter: Jose Centeno, Mott MacDonald.
Topic Area: Building Codes and Building Performance

The principle of transit-oriented communities (TOC) is to integrate transit, residential, and commercial spaces, enhancing city neighbourhoods and creating more complete places to live, work and play. The city of Toronto is expecting development of several TOCs in the next 10 years alongside the delivery of new rapid transit projects. In some cases, a TOC building can be an overbuild, with its structure built above the transit station. This can lead to some of its reinforced concrete shear walls being discontinued at the station roof, developing a possible weak storey irregularity as per NBCC 2020. This study describes the seismic design for one such prototype: a 27-storey reinforced concrete TOC structure supported at level 3 by transit station infrastructure - located in Toronto, Canada. Following NBCC 2020 seismic design provisions, the Seismic Force Resisting System (SFRS) must not have a weak-story irregularity.  This study proposes that, generally SFRS consisting of RC shear walls with discontinuities, must address three failure mechanism conditions that can lead to a weak-story: overturning failure, diaphragm failure and wall shear failure. A design methodology is proposed to simplify the design of susceptible structures, addressing each mechanism in turn. The effectiveness of this process is evaluated using incremental dynamic analysis.  The study finds that providing the necessary distribution of wall strength and capacity design of the transfer diaphragm can be critical in preventing a weak story failure. While the Canadian Concrete Code (CSA A23.3) may allow for an upper bound design limit for diaphragm design, this study concludes that with discontinuous walls, this may be insufficient in preventing a weak story failure. The study’s findings indicate that the proposed methodology could potentially enhance the seismic design of SFRS with discontinuous RC walls. However, additional research is necessary to evaluate its practical application.

12. Seismic Design Criteria for Functional Recovery Performance
Presenter: Kristen Blowes, University of British Columbia, Vancouver.
Topic Area: Building Codes and Building Performance 

Structural strength and stiffness requirements currently codified in seismic design provisions in the United States aim to protect life-safety, but do not ensure tenant recovery following an earthquake. With the development of new recovery-based design provisions, there is an ongoing effort to assess the impact of designing for stricter strength and stiffness requirements on functional recovery time. In this study, we assess over 20 systems currently codified in ASCE 7-22 with (1) increased design strength requirements, (2) reduced drift limits, and (3) enhanced nonstructural component detailing. Representative engineering demand parameters are used to estimate structural and nonstructural component damage and resulting functional recovery times using the ATC 138 methodology, as implemented in the Seismic Performance Prediction Program (SP3). Functional recovery time results are then used to develop structural system design criteria and nonstructural component design requirements. Results of this study will ultimately support the upcoming 2026 NEHRP design recommendations.

13. Building Code Compliance: Impact on Seismic Risk in Alaskan Housing
Presenter: Maria Jose Echeverria, University of Colorado Boulder.
Topic Area: Building Codes and Building Performance

This study examines the performance implications of compliance with building code seismic requirements for Alaskan housing. While building codes and standards offer strategies for achieving safety and resilience of structures, and most people care about and expect safe housing, adherence to these strategies is inconsistent or absent in many places. For example, in Alaska, which is at risk from the significant hazard of earthquakes common in the Pacific Northwest, some jurisdictions mandate and enforce modern codes with plan reviews and inspections. However, others lack the capacity or regulatory will to define and regulate housing construction, a concern due to the state's seismic risk. This study aims to scrutinize the implications of non-compliance with codes by examining key hazard-resistant building practices in Alaska and assessing their impact on seismic risk mitigation. We conducted fieldwork and interviews to identify key housing construction practices for seismic design, emphasizing practices that, although vital, are not always present. Common deficiencies identified were inadequate shear wall quantities and distributions, incorrect aspect ratios for shear walls, inappropriate thickness for wood structural panels, and inadequate fastening. Then, we evaluated the potential risk reduction achieved through compliance, relative to the baseline of typical building practice, with these practices across various housing designs representing Alaskan construction. These typologies encompass a range of design considerations relevant to seismic resistance. The study quantifies risks of structural collapse and housing functionality loss through performance-based engineering and nonlinear simulation models. The findings underscore the significance of compliance with hazard-resistant building practices in Alaskan housing and advocate for minor yet crucial practice modifications to enhance the safety and resilience of these structures. While the study is centered in Alaska, its findings highlight the importance of hazard-resistant practices applicable to wood frame housing and underscore the need to protect vulnerable communities, irrespective of regional regulatory differences.

14. Comparison of Recovery Time Prediction Methodologies using Observations from December 2022 Ferndale Earthquake
Presenter: Jakub Valigura, Arup and SEAONC.
Topic Area: Climate, Multi-hazard Modeling, and Earthquake Resilience

Many recent earthquakes around the World have shown that while our building codes may be adequate in protecting lives, they are not adequate from a community resilience perspective. Function of services and hence buildings that house them is essential for community resilience. Several methodologies have been recently developed that can guide and help structural engineers to design buildings with explicit recovery time goals. Among the most used are ATC-138 that expends on FEMA P-58 framework, Resilience-Based Earthquake Design Initiative (REDi), TREADS developed by researchers at University of British Columbia, and F-REC. The outcome of each of these methods is prediction of recovery time. However, the assumptions and details of calculations within each differ. The intent of this poster and presentation is to provide a comparison of these methods. First on methodology level – the assumptions and details of the methods will be compared. We will highlight commonalities as well as points of departure between the methodologies. The second part of the paper will examine recovery time results and compare them between the methods and to real world example. To that, we will use recordings from instrumented building that withstand the December 2022 Ferndale earthquake. The recordings are publicly available. The building was examined after the earthquake and hence the extent of damage and recovery times are known. The analysis will be performed by both methodologies developers as well as practicing engineers to further compare the relative differences between the users.

15. Towards Linking Hydroclimatic Change and Earthquake Hazard in Hawke’s Bay, New Zealand
Presenter: Kaleigh Yost, The Pennsylvania State University.
Topic Area: Climate, Multi-hazard Modeling, and Earthquake Resilience

Many regions with high earthquake hazard are also experiencing severe impacts from climate change, including increasingly frequent and severe hydroclimatic events. For example, the Hawke’s Bay region on the East coast of Aotearoa, New Zealand’s North Island, has high earthquake hazard due to its proximity to the Hikurangi Subduction Zone. The 1932 Mw 7.8 Hawke’s Bay Earthquake caused severe damage to the city of Napier and remains the deadliest natural disaster in the country's history. More recently, the unprecedented Cyclone Gabrielle moved across the North Island in February 2023, through Hawke’s Bay, and caused an estimated $8 billion in storm and flooding damages. As communities in Hawke’s Bay begin to rebuild post-cyclone, it is paramount that adaptations for flooding and storm events also incorporate considerations for the ongoing seismic threat to the region. Further, it is necessary to consider how hydroclimatic changes will impact coseismic hazards like soil liquefaction. In this project, we aim to quantify (1) how groundwater and soil profile saturation in Hawke’s Bay is influenced by seasonal fluctuations, future sea level rise, and increasingly severe storm events, and (2) how these changes in groundwater impact liquefaction hazard in the region. In this presentation, we describe our ongoing field testing program designed to quantify the geotechnical and evolving hydrological conditions at two case study sites that had observations of liquefaction after the 1932 earthquake. The outcomes of this project will support the building of sustainable and resilient communities that can anticipate and mitigate the multi-hazard threats of the future.

16. Simulating multiple disaster effects in Southern California
Presenter: Mustafa Arghistani, University of Bologna, Italy. 
Topic Area: Climate, Multi-hazard Modeling, and Earthquake Resilience

Natural disasters, e.g., earthquakes and coastal flooding, pose significant threats to coastal cities on the West coast. Whilst remarkably challenging, the modeling of multiple disaster effects in coastal areas has been recently deemed essential to support decision-making in preparedness and mitigation of low probability and high consequence disasters. With the main intent of informing and inspiring possible mitigation actions, the study presented herein explores the effects of multiple disasters in Southern California, while dismissing any vain aim of being a truthful representation of future events. The city of San Diego, critically located in a border region, is chosen as a preliminary focus of this study as it is exposed to multiple natural hazards, including earthquakes originating from the San Andreas fault, and the risk of coastal flooding due to rising sea levels and storm surges. Amongst the available simulation tools, HAZUS MH by the Federal Emergency Management Agency (FEMA) is used for its versatility and ease of implementation, which facilitate the integration of various datasets and modeling capabilities and enable a comprehensive analysis of disaster scenarios. By simulating the effects of earthquake and coastal flooding events, this research informs on the often overlooked but particularly devastating potential compound impacts of multiple events, with emphasis on assessing the vulnerability of local communities and understanding the cascading effects of damage to the civil infrastructure on the recovery efforts. The results show that particular focus should be given to the transportation infrastructure, as this plays a critical role in disaster resilience, being essential for maintaining connectivity and facilitating emergency response. This research shows that understanding how damage to transportation infrastructure affects recovery efforts is crucial for an efficient resource allocation and rapid restoration of essential services after disaster events.

17. Quantifying Community-Scale Functional Recovery of Buildings after Earthquakes
Presenter: Pouria Kourehpaz, The University of British Columbia.
Topic Area: Climate, Multi-hazard Modeling, and Earthquake Resilience

Post-earthquake functional recovery of buildings plays an integral role in community resilience. While rigorous methodologies have been proposed to assess the recovery trajectories of individual assets, community-scale functional recovery assessments involve multifaceted complexities (e.g., various levels of spatial correlations, and Interdependencies) and remain underexplored. This study proposes a computational framework to extend the building-level recovery assessment framework, TREADS (Tool for Recovery Estimation And Downtime Simulation), to community-scale assessments. The concept of repair class is redefined at a building level rather than at a component level to identify the recovery state hindered by the extent of damage to the building. Distinct asset-level fragility models are generated for each repair class and integrated with an appropriate consequence model to estimate earthquake-induced repair times. The total downtime to functional recovery for each building is then computed by combining repair times and the delays caused by impeding factors that occur before repairs commence, such as inspection, financing, and contractor mobilization. The temporal recovery trajectory at the community scale is estimated by considering buildings with various occupancy types. Additionally, resource limitations in the region and correlations between impeding factors across buildings are considered. The proposed framework is implemented in downtown Vancouver, BC, Canada, encompassing buildings from different eras, construction materials, and occupancy types. This research can offer valuable insights to inform policy decisions toward accelerating post-earthquake community recovery and enhancing resilience.

18. Sensitivity of seismic ground response analyses of marine land reclamation profiles to the consideration of earthquake causal rupture parameters in selection of input ground motions
Presenter: James Dismuke, Schnabel Engineering. 
Topic Area: Geotechnical Engineering

Seismic ground response analyses are typically performed to assess the nonlinear dynamic behavior of soils in the design of marine land reclamations in high seismicity regions. These analyses require a selection of input ground motions, for which seismic design codes generally recommend having seismic-hazard-consistent earthquake causal rupture parameters, such as rupture mechanism, magnitude, and source-to-site distance. This study investigated the impact of including earthquake causal rupture parameters in input ground motion selection criteria on the results of one-dimensional and two-dimensional seismic ground response analysis of marine land reclamation profiles. Multiple seismic ground response analyses were performed to cover a range of marine land reclamation soil conditions and response spectral amplitudes. Candidate ground motion catalogues were developed considering hazard-consistent secondary intensity measures, both with and without bounds placed on earthquake causal rupture parameters. Sets of ground motions were selected from these catalogues based on their fit with the respective target response spectrum. Input-to-surface amplification factors and permanent horizontal crest displacements were calculated for the various input ground motions and marine land reclamation profiles. The results of the analyses were compared to assess the differences in responses calculated with input motions selected using the different approaches for considering earthquake causal rupture parameters.

19. VS30-based relationship for Chinese site classification
Presenter: Junju Xie, Institute of Geophysics, China Earthquake Administration.
Topic Area: Geotechnical Engineering

Classification of engineering sites is essential when considering site conditions for seismic fortification in seismic design codes. However, because of the different site classification methods currently used, it is difficult for the seismological and engineering communities in China to share site metadata (e.g., site classes) and relevant results with the international communities.This issue also prevents the Chinese communities from utilizing the well-established models that are based on the time-averaged shear wave velocity for the top 30 m (V_S30). We first assembled the shear wave velocity (V_S) profile data from various sites in China, Japan and California, to study the statistical characteristics of V_S30 and the equivalent shear wave velocity (V_Se, time-averaged within soil layers for no more than 20 m). We found that a single V_Se parameter was insufficient to distinguish between the different Chinese site classes, especially for site classes III and IV that consider soil layers deeper than 20 m. However, the V_S30 values for the Chinese site classes from I_0 to IV exhibit significant distinctions. We developed a new V_S30-based site classification system for the Chinese sites. We determined the boundaries of V_S30 between the Chinese site classes by maximizing the rate of correct classification. Our new system of classification facilitates the connection of Chinese site classes with well-developed V_S30-based models and site data sharing between Chinese and international scientific communities.

20. Liquefaction Resistance of Cemented Sands
Presenter: Laura MC Luna, University of California, Davis.
Topic Area: Geotechnical Engineering

Soil liquefaction during seismic shaking poses a significant geohazard, having the potential to lead to extensive infrastructure damage during earthquake events. As a result, a reliable assessment of the potential for soil liquefaction is crucial in evaluating seismic risk. Liquefaction triggering relationships primarily rely on case histories that are most abundant for young, uncemented sands. However, quantifying the effects of soil cementation on cyclic resistance is challenging because of the limited case histories available, and the difficulties in soil sampling without destruction or damage to the cementation bonds. The burgeoning field of bio-cementation has led to the availability of an unprecedented laboratory dataset on the dynamic behavior of cemented sands. This poster leverages the results from an extensive cyclic direct simple shear (DSS) testing program on bio-cemented sands to explore the effects of soil cementation on liquefaction resistance. A relationship is established between the level of cementation (expressed as the ratio of the cemented to uncemented shear wave velocity), the number of cycles to liquefaction, and the cyclic resistance based on available data. The cyclic resistance under cemented conditions is then compared against the baseline uncemented scenario, quantifying the improvement ratio associated with each level of cementation. These findings offer valuable insights into cementation effects, informing future studies on natural cementation and bio-mediated ground improvement techniques.

21. Cementation and Bond Degradation of Biocemented Sands
Presenter: Piyush Vyas, University of Southern California (USC).
Topic Area: Geotechnical Engineering 

Biocementation has emerged as a potentially environmentally sustainable ground improvement technique with promising practical applications such as liquefaction mitigation, erosion control, and construction material creation. However, prior to implementing this innovative technology in the field it is essential to assess the degradation behavior of calcite bonds in biocemented sands. This research delves into the influence of cementation and bond degradation on the mechanical properties of soils, with a particular focus on the initial shear modulus (G_max) as an indicator. Resonant Column tests are performed to determine G_max . This study utilizes Enzyme Induced Calcite Precipitation to induce cementation between sand particles. The study explores bond degradation and cementation effects in moderately and lightly treated sands. The stress-strain behavior of biocemented sand is influenced by several mechanisms, primarily cementation bonds and interparticle stress (especially following bond degradation). To investigate, test specimens with three levels of cementation (0,1 & 3% Calcite Content) are prepared under a confinement pressure of 50 kPa, followed by incremental stress with increment of 10kpa, after the treatment. At each stress level, G_max is estimated, shedding light on the variation of G_max with stress level and its correlation with the phenomena of cementation and bond degradation. The overarching goal of this study is to determine the stress level at which cemented sand transition’s to uncemented sand behavior and how this varies with relative density. The identified threshold signifies the point at which influence from bonds have been superseded by friction from interparticle stress, which provides a material constraint for engineering analysis and design.

22. Consistently estimated ground motion intensity measures at liquefaction case history sites
Presenter: Renmin Pretell,  University of Nevada Reno. 
Topic Area: Geotechnical Engineering

The state of practice for assessing liquefaction triggering relies on relations that use the peak ground acceleration (PGA) at the ground surface and the earthquake magnitude (M) to represent the seismic demand leading to liquefaction or lack thereof. PGAs at liquefaction case history sites have often been taken as equal to the PGA at the nearest seismic station, sometimes with 1D site response analyses to account for differences in site effects. When a seismic station was unavailable, ground motion models (GMMs) or judgment were used. These traditional approaches fail to account for one or both of the following: (1) The differences in path and site effects between the liquefaction site and the nearest ground motion recording, and (2) the PGA spatial correlation. Furthermore, alternative ground motion intensity measures (IMs), such as cumulative absolute velocity (CAV), may be more efficient for predicting liquefaction triggering, but they are unavailable. This study addresses these limitations. A consistent approach for computing ground motion IMs is presented, and four ground motion IMs are computed at liquefaction case history sites in the Next Generation Liquefaction (NGL) database, namely PGA, peak ground velocity (PGV), Arias Intensity (I_a), and CAV. This framework adjusts ground motion IMs estimated using GMM by correcting the expected over- or underprediction. The newly estimated ground motion IMs show discrepancies when compared against legacy values. A comparison of the newly estimated and legacy PGAs shows discrepancies ranging from 50 to 200%. This finding suggests the need for revisiting such models or developing new ones. An openly accessible tool for the utilization of the presented framework is introduced.

23. Validating Liquefaction Case Histories using Earthquake Simulations: 1933 Long Beach Earthquake
Presenter: Sajan K C, University of Southern California (USC). 
Topic Area: Geotechnical Engineering

The Los Angeles basin lies in an active tectonic region and accommodates the second largest population in the United States. Several historical earthquakes have revealed the susceptibility of significant portions of the basin to liquefaction. Among them is the M_w 6.4 Long Beach California earthquake that occurred on March 11, 1933. Liquefaction was reportedly observed at several locations within a distance range of 12 to 15 km from the Newport-Inglewood fault, most of which were close to the coast. The earthquake was recorded by only three strong motion seismometers. However, there is low confidence regarding the quality of the recorded strong motions due to the limitations of the instruments (i.e., clipping of both horizontal components of the recordings). Earthquake simulations have yet to be used to study liquefaction for events with very sparse ground motion recordings, at least in the Southern California region. This study aims to evaluate the efficacy of employing earthquake simulations to assess historic events with observed liquefaction features using documented information from the 1933 Long Beach earthquake. The rupture scenario, as developed by Hough and Graves (2020), for this earthquake will be leveraged to generate synthetic waveforms using the broadband platform. The generated waveforms will be used to conduct 1D site-specific response analysis at locations where liquefaction was observed. These efforts will be supplemented and complimented using field based measurements, which will be procured from literature where available or gathered using passive techniques (temporary seismometers). Using the resulting hazard characterization from the earthquake simulations, an estimate of the spatial distribution of liquefaction will be provided for the 1933 Long Beach event.   

24. Assessing Emergency Healthcare Accessibility in Metro Vancouver, BC under M9 CSZ Earthquakes
Presenter: Kiranjot Kaur, University of British Columbia. 
Topic Area: Lifelines

Given the proximity of Metro Vancouver, BC to the Cascadia Subduction Zone (CSZ), capable of producing Magnitude 9 earthquakes, understanding the seismic performance of the region’s critical infrastructure including healthcare and transportation systems is an important endeavour to inform owners and emergency planners. This poster presents a framework for performing a regional assessment of the accessibility of emergency healthcare facilities in Metro Vancouver, BC under a suite of 30 physics-based ground motion simulations of M9 CSZ earthquakes. In partnership with infrastructure owners, this assessment is based on real data from Metro Vancouver. The framework assesses the performance of buildings on hospital campuses and bridges on the major road network using the NHERI-SimCenter R2D tool, a state-of-the-art application for seismic risk assessment. Accessibility is assessed using a two-step floating catchment area analysis of the regional road network, as implemented in ArcGIS. Damage state estimates for hospital buildings are used to estimate a reduction in hospital capacity. Damage states for the bridge assets that lead to safety concerns are modeled on the road network as inaccessible nodes and links. Using the two-step floating catchment area analysis, a comparison of accessibility is performed for four scenarios: (1) baseline analysis (no damage), (2) considering hospital damage, (2) considering bridge damage and (4) considering both hospital and bridge damage. The poster presents a novel assessment of assets in Metro Vancouver under M9 CSZ physics-based ground motions and brings together both building damage and transportation analysis to measure healthcare accessibility. The results demonstrate the importance of examining interdependent systems when performing regional assessments and can be used by infrastructure owners and emergency managers to better understand the potential impacts of major earthquakes on healthcare accessibility in Metro Vancouver.

25. Prioritizing buildings for retrofit considering new sediment thickness maps for Massachusetts combined with existing liquefaction hazard maps and high resolution fo data for Greater Boston
Presenter: Christina Sanon, Tufts University
Topic Area: Multidisciplinary

When an earthquake occurs, local site conditions can contribute to structural damage through soil amplification and liquefaction. In light of growing recognition of seismic vulnerabilities in regions historically considered “low risk,” this poster presents a high-resolution seismic hazard assessment for use as a building vulnerability assessment for the commonwealth of Massachusetts. The seismic landscape of the state, while not traditionally associated with high seismic activity, combined with the high percentage of unreinforced masonry structures, demands a proactive approach for identifying at-risk structures to ensure resilience in the face of potential earthquakes. Using the 2023 National Seismic Hazard Maps published by the USGS with the 2020 NEHRP recommended seismic provisions in the ASCE 7-22 design code, and recently published state-wide NEHRP site conditions map (Pontrelli et al. 2023), we first establish the design shaking levels across the state. The state-wide NEHRP site conditions map relies on a newly published high resolution sediment thickness map of Massachusetts (Mabee et al., 2023) and regional geophysical data to estimate sediment velocities (Vs_avg) and fundamental site periods (f_o) (Pontrelli et al. 2023). In addition, we include high resolution liquefaction hazard and f_o maps for Greater Boston. For demonstration, we evaluate a state-wide building inventory and establish a vulnerability index that includes shaking hazard, liquefaction hazard, and soil-building resonance hazard. Given that the site conditions in Massachusetts are known to lead to strong soil resonance due to large impedance contrasts at the soil and bedrock interface, we investigate the prevalence of soil-building resonance across the building inventory.

26. Using ShakeAlert Earthquake Early Warning to Reduce Earthquake Losses
Presenter: Gabriel Lotto, University of Washington.
Topic Area: Multidisciplinary

The ShakeAlert Earthquake Early Warning System, managed by the US Geological Survey and several partner universities across the West Coast, is currently operational in Washington, Oregon, and California. It detects earthquakes and triggers alerts and automated protective actions, giving individuals and organizations seconds to tens of seconds of advance warning before shaking begins. A well-known use of the ShakeAlert System is cell-phone based alerting via apps and operating systems. A lesser-known application involves using ShakeAlert Messages to trigger customized, automated actions that protect utilities, transportation networks, infrastructure, and schools. This poster will examine case studies of technical applications of earthquake early warning systems in the US, and discuss the information pathways involved in turning seismic shaking into protective actions.

27. NDSHA Scenario Seismic Hazard Map, Vancouver, b.c. Area: XeRis Methodology
Presenter: James Bela, International Seismic Safety Organization / Oregon Earthquake Awareness.
Topic Area: Multidisciplinary

Neo-Deterministic Seismic Hazard Assessment NDSHA is the new multi-disciplinary scenario- and physics-based approach for the evaluation of seismic hazard and safety—with demonstrated "Overall Prediction Accuracy and Simulation Validation for Real-World Applications”. Building upon a long experience of successful practice with DSHA, NDSHA now convolves a comprehensive physical knowledge of: (i) seismic source process; (ii) propagation of earthquake waves; (iii) combined interactions with site conditions—and thus effectively accounts for the tensor nature of earthquake ground motions. Standard NDSHA, using geological and geophysical data, computationally estimates an envelope of scenario ground-shaking characteristics from both: (1) the largest historically observed earthquake within a region; and (2) also from the Maximum Credible Earthquake MCE. Because each scenario is always “a real earthquake”, it therefore does not require considerations of either probabilistic hazard model temporal representations of earthquake “likelihood”, or scalar empirical GMPEs. Some NDSHA applications performed at an international level will be presented, together with some preliminary results for ground shaking scenarios in both the Vancouver Island and Vancouver, BC mainland areas. Earthquakes and Sustainable Infrastructure presents a new NDSHA paradigm for seismic safety - detailing in one volume the ‘state-of-the-art’ scientific knowledge on earthquakes and their related seismic risks, and the actions that can be taken to reliably ensure greater safety and sustainability. Thirty chapters of the book provide comprehensive reviews and updates of NDSHA research and applications so far in Africa, America, Asia and Europe — evidences and case histories illustrating the overall prediction accuracy of NDSHA and its robust validation for real-world applications leading to more reliable procedures for seismic hazard assessment evaluations. 

28. Advancing the Use of Scenarios in Mitigating Earthquake Risk
Presenter: Janise Rodgers, GeoHazards International.
Topic Area: Multidisciplinary 

Scenarios of hypothetical disasters and their impacts have been prepared and used for over 50 years. Our work explores how lessons from past geologic hazards scenarios and new advances in adjacent practice domains from risk communication to multi-hazard modeling can advance the use of scenarios for pre-disaster mitigation. With support from the U.S. Agency for International Development and the U.S. Geological Survey, we interviewed 158 scenario users and developers across Ecuador, Nepal, New Zealand; and California, and reviewed literature on (a) scenarios and scenario-component studies; (b) scenario impacts; and (c) eight topic areas in which advancements may contribute to more effective geologic hazards scenarios: community engagement at the grass-roots level; risk communication; public policy; guidance for scenario-based mitigation planning; multi-country, cross-border scenarios; secondary or induced hazards; multiple scenario approaches and robust scenario event selection within a single hazard; and methods for using scenarios across multiple geologic hazards. Key findings included the critical importance of co-production with local stakeholders, who should be involved from the beginning of scenario efforts; the usefulness of two-way communication about risks and impacts, in concrete terms meaningful to decision-makers; credibility being strongly related to scientific quality (judged by reputation of the developer, scientific consensus, and data quality), relevance, plausibility, among other factors; and that scenarios were part of a complex mix of influences that led to mitigation programs being implemented, with significant advocacy effort required for success. Based on these findings and a series of practitioner workshops, we ideated improvements to scenario development practice and prepared a guidance document. Key improvements we recommend include a focused co-production effort beginning at the planning stages, including a strong commitment to creative, joint solutioning; early engagement of decision-makers and an orientation toward action; and methods to more broadly consider multiple scenarios, including from different hazards.

29. Bridging the gap between engineering and society: communicating earthquake risk via media
Presenter: Alyssa Yearick, San Diego State University.
Topic Area: Multidisciplinary

To minimize the impacts of disasters, it is crucial to understand how effectively information is communicated, especially in the context of seismic events and for a broader range of communities, including those with minority-majority populations. Recent global disasters, e.g., the 2023 Turkey earthquake sequence and the 2021 Haiti earthquake, underscored the urgent need to educate society about preparedness; specifically, clear discursive constructions in natural disasters established at the scientific level are necessary to develop effective, diverse and inclusive information strategies to address language barriers during times of crisis, ultimately reducing injuries, minimizing property damage, and providing diverse communities with long-term seismic resilience. In the context of the pre-event phase, this project leveraged the collaboration between journalism and earthquake engineering researchers to investigate how earthquake-related information is conveyed and received amongst diverse communities. Considering that risk perception varies temporally and within cultural context, this research focused on understanding earthquake risk communication in the San Diego region, where approximately one-third of the population is Spanish-speaking, and more than 100,000 people cross the US-Mexican border every day to go to school and/or work. An M6.9 earthquake scenario simulation for the Rose Canyon fault, running through downtown San Diego to Mexico, was first considered to quantify the local earthquake risk and identify the communities critically affected. Further, by analyzing media coverage of earthquake risk over the past decade, this research explored strategies for effectively communicating seismic risk to the diverse population in San Diego, also seeking feedback within the community. The results of this multi-level analysis highlight the importance of developing diverse and inclusive approaches to effectively convey essential seismic risk information and creating a communication landscape able to minimize disruptions, accelerate recovery, and contribute to the preparation efforts of the San Diego 2050 vision.

30. Practical Applications of Non-Ergodic Seismic-Hazard Analysis
Presenter: Bahareh Heidarzadeh, ENGEO Incorporated.
Topic Area: Other 

Ground-motion models (GMMs) are generally based on the ergodic assumption wherein global averages and aleatory variability from global datasets are assumed to be applicable at a site of interest. In reality, there are generally systematic differences between the GMM predictions and observed ground motions at a site of interest. To overcome this issue, non-ergodic methodologies have become more common. Non-ergodic approaches involve refinement of one or more of the terms in the GMM (i.e., source, path, and site) and allow for the use of a lower aleatory variability. This poster focuses on practical applications of non-ergodic methodologies. There is a focus on refinement of the GMM site term, which is the most commonly refined GMM term in practice. The poster presents multiple case histories that illustrate similar trends, wherein the ergodic models underestimate spectral accelerations at the fundamental site period and overestimate spectral accelerations over other broad period ranges.

31.Incorporating centrifuge tests and simplified tools to analyse complex 3D seismic soil-structure interaction of offshore foundations
Presenter: James Go, Arup.
Topic Area: Other

Resilient renewable energy is key to the world’s energy transition and offshore wind is crucial to a successful energy transition. As offshore wind farms are built in highly seismic areas, the renewables industry needs cost-effective methods to ensure the safety of wind turbines under earthquake loading. Together with industry and academia, Arup has developed cost-effective design methods to analyse a complex nonlinear problem. Current codes offer limited guidance on soil-structure interaction under seismic loading. Performing time history analysis of full three-dimensional (3D) dynamic soil-structure interaction (DSSI) models provide the most accurate method for the seismic assessment of offshore wind turbines. However, 3D DSSI is a computationally intensive and timeconsuming process and demands a high level of seismic, structural and geotechnical expertise. Another challenge is the lack of actual records of offshore wind turbines undergoing earthquake loading. The lack of case histories require validation of the assumptions and methods used in the design methodology using physical tests. To address these challenges, Arup, together with our client and collaborators, applied the following strategy: 1. Validation of 3D DSSI using centrifuge testing; and 2. Calibration of simplified beam-on-nonlinear spring using 3D DSSI. By combining the use of centrifuge testing and simplified models, Arup and its partners were able to increase the efficiency of performing DSSI analyses, reduce the cost of setting up complex 3D DSSI models, and ultimately improve the safety of offshore wind turbines under seismic loading. This work is being shared in a joint industry project to update recommended practice for the seismic design of offshore wind power plants.

32. Implementing Rupture Directivity Effects Into PSHA
Presenter: Jeff Bayless, AECOM
Topic Area: Other 

The effects of rupture directivity on near-fault ground motions are known to be significant and should be included to accurately estimate the hazard, especially for long-period ground motions (Abrahamson, 2000). However, these effects are not explicitly accounted for in typical ground motions models, and therefore not in typical probabilistic seismic hazard analyses (PSHAs) because substantial confusion exists in practice about which directivity models to use and how to apply them to the median and aleatory variability of GMMs, especially to complex multisegment rupture models (Donahue et al., 2019). In the response spectral approach, which we adopt, rupture directivity effects are considered by including adjustment factors to the elastic acceleration response spectrum at 5% damping. This approach lends itself readily to inclusion into PSHA (Rodriguez-Marek and Cofer, 2009). This work describes an update to our 2020 rupture directivity model (Bayless et al., 2020), including formalized instructions for adjustments to the median and aleatory variability of the ground motion model to which it is applied. Additionally, we provide guidance on implementation, including deterministic and probabilistic applications, and methods for modeling hypocenter locations and multi-segment ruptures. The result is a comprehensive model suitable for use in future PSHAs, including those performed as part of the USGS National Seismic Hazard Model. The model applies to strike-slip earthquakes only. A future update will address directivity effects for other styles of faulting.

33. Large-scale experimental testing of segmented braces for post-earthquake repair of concentrically braced frames
Presenter: Willy  Mrema, Marquette University.
Topic Area: Post-earthquake emergency response/planning

Special concentrically braced frames (SCBFs) designed to the minimum seismic loads defined by ASCE/SEI 7 are expected to sustain damage in large earthquakes due to yielding, buckling, and fracture of the braces. This inelastic action is intentional, as it provides a mechanism for energy dissipation and helps limit demands elsewhere in the structure, but braces that have sustained significant yielding, residual deformation, or fracture will require repair to restore resistance and ductility. While component replacement is an obvious repair strategy for these systems, this is potentially difficult and costly due to member size and accessibility limitations (e.g., presence of architectural finishes). However, the most severe brace damage is typically concentrated near the midspan, where local deformations develop and eventually precipitate fracture due to low-cycle fatigue; therefore, damage in this region is the primary motivation for post-earthquake repair. To facilitate repair of SCBF braces and hence return to building functionality, the efficacy of a proactive, repair-oriented design approach with segmented (spliced) braces is under investigation in a current NSF-funded research program. These segmented braces allow for rapid replacement of the brace midspan segment while retaining other components of the SCBF (brace end segments, connections, beams, and columns). Large-scale experimental testing of SCBFs with segmented, hollow structural section (HSS) braces is being conducted at the Marquette University Engineering Materials and Structural Testing Laboratory. The test specimens consist of a one-story, single-bay SCBF with one diagonal brace. The frames are loaded quasi-statically using a fully reversed, cyclic loading protocol to impose deformations consistent with large seismic demands. The tests are intended to validate the seismic behavior of SCBFs with segmented braces in both as built and post-repair conditions to ensure that the proposed repair strategy is capable of restoring sufficient strength, stiffness, and deformation capacity.

34. Earthquake Loss Estimations for Istanbul in Pre- and Co-Seismic Phases
Presenter: Ufuk Hancilar, Bogazici University.
Topic Area: Risk Modeling and Insurance

Istanbul, with its history dating back 8,000 years and a population exceeding 16 million today, is under the threat of an M7+ earthquake that may occur in the branches of the North Anatolian Fault System in the Marmara Sea. Intensive and comprehensive efforts are underway for risk mitigation, emergency response management and ultimately to make Istanbul earthquake resilient. This paper provides recent outcomes of our long-lasting studies for earthquake risk assessment of Istanbul. Probable loss estimations based on several scenarios are presented in terms of number of causalities, damages in the building inventory, infrastructure systems (i.e. sanitary and waste water, natural gas, electricity and roadway networks), historical and cultural heritage and in the industry, as well as the resulting economic losses. The components, working algorithm and the outcomes of the Istanbul Earthquake Rapid Response System, which is operational 24/7 online mode, are also introduced.

35. The Center for Collective Impact in Earthquake Science (C-CIES): Transforming Earthquake Science and Engineering
Presenter: Aaron Velasco, University of Texas at El Paso.
Topic Area: Seismology and Earth Science

The Center for Collect Impact in Earthquake Science (C-CIES), a catalyst project funded by the National Science Foundation, is working toward becoming a full-fledged interdisciplinary research center that focuses on high-impact, low-probability earthquakes, with an emphasis on community engagement. The mission of C-CIES is to foster inclusive earthquake science with the aim of increasing resilience in regions under-prepared for earthquakes. C-CIES aims to create an interdisciplinary research center that embodies a collective impact framework to improve understanding of earthquakes and associated hazards in an equitable, accessible, and sustainable manner. C-CIES will conduct fundamental earthquake science and develop strategies for better identifying and quantifying seismic hazards in several focus regions including Puerto Rico, the Intermountain West, the Central U.S., and the Eastern U.S. We will extend those results to apply to many other regions of the world. Using collective impact, C-CIES’s research will prioritize the needs of vulnerable populations that have been historically underserved by current earthquake science, engineering, and public policy. To accomplish its vision and mission, C-CIES currently funds pilot projects that address critical earthquake science questions with strong social impact and community engagement plans. All research projects will be evaluated using the five elements of collective impact: common agenda, mutually reinforcing activities, shared metrics, and the backbone organization. We believe incorporating collective impact and fostering inclusive earthquake science will transform how earthquake and associated hazard science is being conducted, leading to fundamental breakthroughs that will profoundly and positively impact communities throughout the country.

36. Prediction of Ground-Motion Mean Period for Cascadia Subduction Earthquakes
Presenter: Emrah Yenier, PhD, Poster, Second Call.
Topic Area: Seismology and Earth Science

Mean period (T_m) is used as a scalar measure of ground-motion frequency content for estimating the seismic demand on geotechnical and structural systems. T_m is defined as the weighted-average period based on Fourier amplitudes (Rathje 2004). Current predictive models have been evaluated on crustal or global subduction earthquake datasets. In this study, we developed a regional predictive model of T_m for Cascadia Subduction Zone earthquakes. We used ground motions from the Cascadia Subduction Zone available in the NGA-Subduction dataset (Mazzoni et al. 2022). Most recordings were obtained from intra-slab events with magnitudes between M4 and M7. We supplemented these records with synthetic ground motions compiled from the M9 Project (Frankel et al., 2018). Our predictive model accounts for the effects of source, path, and local site condition on T_m. For hazard-significant earthquake scenarios in Pacific Northwest, we found that T_m attains comparable values (i.e., 0.4 to 0.6 seconds) for interface and intra-slab events at non-basin sites. They are similar to the mean period estimates for shallow crustal earthquakes based on Du (2017). However, within the Seattle Basin, a strong influence of deep sediments on T_m is observed for interface events. Interface events attain notably larger mean periods (i.e., approximately 2.0 seconds) than intra-slab and crustal events (i.e., approximately 0.5 to - 0.7 seconds) at sites where the sediment thickness is greater than 6 km. These findings highlight the significance of ground motions from Cascadia Subduction Zone interface events with rich long-period content in Seattle area, especially for structures and slopes that are heavily influenced by the frequency content of expected ground motions.

37. School Lessons Learned - Case Studies of Oregon State School Building Retrofits
Presenter: Eddie Vega, Holmes US. 
Topic Area: Structural Engineering

This poster presentation highlights case studies of multiple seismic retrofit projects done in the State of Oregon by Holmes US. This poster will discuss different retrofit needs, project schedule constraints, various funding systems and other related topics for the school projects of focus. These school retrofit projects span over multiple years and different aspects of the various phases will be highlighted from planning, design, and construction. The presenter, Eddie Vega, is a structural engineer with Holmes US. He has been passionate about seismic safety in schools since getting involved with EERI’s School Earthquake Safety Initiative in 2014.

38. Damage Assessment for Balloon-Type CLT Shear Wall Systems Subjected to M9 Earthquake Scenario
Presenter: Ehsan Ferdosi, UBC.
Topic Area: Structural Engineering

The use of Engineered Wood Products is growing heavily in large and tall structural applications due to their high strength-to-weight ratio, versatility for prefabrication, and carbon and energy efficiency. However, for more widespread adoption, more comprehensive assessments are required to address all sensitive aspects of using this material. For instance, the performance of the structures that utilize heavy or mass timber products in their Seismic Force Resistant Systems (SFRS) in seismic-prone areas is still widely unknown. In addition, with the new seismic performance measures, like seismic resilience, more effort is needed to assess the seismic performance of engineered timber structures. This study focuses on damage assessment for engineered timber structures after a seismic event. In this regard, the performance of a conventional timber-based structural system is compared to a more resilient hybrid option in terms of the damage state of the structural elements of the SFRS when subjected to the M9 earthquake scenario. A monolithic balloon-type CLT shear wall system with dowel-type hold-downs represents the conventional construction practice. In contrast, a double CLT shear wall system with link beams and the same hold-downs represents the hybrid option. For comparison, 10-story archetypes are designed for each structural system. Afterward, probabilistic seismic performance evaluation for each structural system is performed considering uncertainty in the hazard source, structural performance, and occurrence of the damage. The results show that the elements of the hybrid system sustained far less damage compared to the conventional system, demonstrating the effectiveness of the resilient solutions. Additionally, the study confirms that connections play a critical role in achieving more resilience in timber-based structures. Overall, this study provides important insights into the seismic performance of timber-based structures in seismic-prone areas and highlights the need for further research.

39. Multi-angle, nonuniform excitations: Effect on cable-stayed bridges
Presenter: Eleftheria Efthymiou, The University of Texas at Tyler. 
Topic Area: Structural Engineering

The definition of the spatial variability of the ground motion (SVGM) is a complex and multi-parametric problem. Its effect on the seismic response of cable-stayed bridges is important, yet not entirely understood to date. This study presents the effect of the SVGM on the seismic response of cable-stayed bridges by means of the time delay of the ground motion at different supports, the loss of coherency of the seismic waves, and the incidence angle of the seismic waves. The focus is the effect of the SVGM on cable-stayed bridges with various configurations in terms of their length and of design parameters such as the pylon shape and the pylon–cable system configuration. The aim of this study is to provide general conclusions that are applicable to a wide range of canonical cable-stayed bridges and to contribute to the ongoing effort to interpret and predict the effect of the SVGM in long structures. This work shows that the effect of the SVGM on the seismic response of cable-stayed bridges varies depending on the pylon shape, height, and section dimensions; on the cable-system configuration; and on the response quantity of interest. Furthermore, the earthquake incidence angle defines whether the SVGM is important for the seismic response of the cable-stayed bridges.

40. Experimental tests to estimate inelastic displacement demands
Presenter: Fabiola Claure, North Carolina State University.
Topic Area: Structural Engineering

Accurately estimating displacement demands in bridges under earthquake loads is essential to predict damage. Previous studies have shown that current practice can lead to displacement underestimation, which has become a critical issue for the structural engineering community. This underestimation is related to the assumption of the damping model. A nonlinear time history analysis might be the most accurate method to estimate inelastic displacements, but its complexity involves careful attention to the input data. This study investigates the impact of the chosen damping model on the estimation of inelastic displacements by nonlinear time history analysis, considering the ground motion characteristics to which the structure is subjected. The outcomes from the analytical models are compared with the results of the first set of shake table tests performed at North Carolina State University. These tests consist of single-degree-of-freedom reinforced concrete columns, 12 inches in diameter, with a 28-kip mass block on the top. The specimens were subjected to two different loading protocols, consisting of multiple motions with increasing amplitudes. The events selected for the table motion were the 1985 Llolleo and the 1995 Kobe earthquake. The amplitude scales and the events were selected based on the desired limit states to achieve the shake table characteristics and the sensitivity to the damping model variation, which were determined based on the nonlinear time history analysis results. The outcomes provide insights into the most appropriate damping model assumption and essential data for estimating displacement demand to improve structural engineering design practices.

41. Experimental Study on Steel for Seismic Resistance 
Presenter: Ferit Gashi, Sapienza University of Rome. 
Topic Area: Structural Engineering

This paper summarizes the experimental campaign carried out for the development of a new steel energy dissipative devices named Slit Dampers (SDs) designed for earthquake protection of structures. SDs consist in shear steel plates with appropriately shaped cut-out portions of material for allowing maximum spread of plastic deformation along the device and then maximizing the hysteretic dissipative behavior. A total of eighty-two steel shear plates with different openings and thicknesses are tested to investigate their behavior under cyclic pseudo-static loading. Six types steel shear plates are studied, including the SD with narrow slits that divide the plate into rectangular links, and the butterfly fuse with a diamond-shaped opening that create butterfly shape links in the plate. Other varying test parameters are: loading rate, material strength, and the number of in-parallel damper elements. It is expected that the proposed model can be successfully used to predict the behavior of dampers in real-world applications.

42. Mass Timber Walls with Buckling-Restrained Boundary Elements (BRBs): Application to a Three- and a Six-Story Building 
Presenter: Gustavo A. Araújo R., Department of Civil and Environmental Engineering, Stanford University. 
Topic Area: Structural Engineering

Hybrid mass timber-steel systems offer a promising solution, blending the aesthetic and sustainable advantages of timber with the ductility and stable energy dissipation properties of steel. Properly detailed mass timber walls with steel energy dissipators can deform well into the inelastic range during earthquakes with stable energy dissipation and, in some instances, low-damage seismic performance. This poster explores two NSF-funded projects: the Emmerson Lab Launch Initiative (ELLI) and the Converging Design project, both focusing on experimental testing of mass timber walls with steel unbonded buckling-restrained boundary elements (BRBs). ELLI, conducted in October 2022, involved quasi-static cyclic testing of a three-story building at Oregon State University, offering valuable insights into the behavior of mass timber walls with BRBs, including BRB-timber connection design. The findings from ELLI guided the subsequent Converging Design project, set for October 2023. This project will conduct shake-table testing on a redesigned six-story building, involving the deconstruction of the top four stories of the existing NHERI TallWood 10-story building and the redesign of the lateral system in the North-South direction to accommodate BRBs in the first story. The experimental and numerical results from ELLI and Converging Design highlight the potential of integrating BRBs with mass timber walls, showcasing enhanced seismic performance with minimal structural damage.

43. Fiber-Based Seismic Damage Models with Damage Indices for Damage and Collapse Assessment of Reinforced Concrete Bridge Piers
Presenter: Jessica Gonzalez, California State University Long Beach. 
Topic Area: Structural Engineering

Earthquakes can inflict major structural damage to reinforced concrete (RC) bridges, and even more so when they are near-fault earthquakes. Since bridge piers are a vital component of bridges, the purpose of this research is to assess the seismic performance of RC single-column pier-supported bridges with flexural failure under near-fault ground motion by analyzing ductility coefficients and damage indices. To simulate the damage progression of RC bridge piers under earthquake loadings, two innovative nonlinear fiber-based finite element models (FEMs) were proposed. The FEMs also take into account the global buckling of longitudinal steel bars, the cracking and spalling of cover concrete, and the effects of bond-slip. The two nonlinear fiber-based FEMs were titled: model 1 (bond-slip excluded) and model 2 (bond-slip included). Both models underwent nonlinear static cyclic pushover analyses and nonlinear response history analyses. The simulation results were compared with available pseudo-dynamic test results. Model 1 proved to be more optimal than Model 2 when assessing the seismic performance of RC single-column pier-supported bridges under near-fault ground motion. The proposed FEMs can denote the damage state at any stage and the gradual accumulation of damage in RC bridge piers which allows for a more accurate seismic assessment. The proposed fiber based nonlinear FEMs, along with the use of ductility coefficients and proposed damage indices, can support engineers when assessing the damage state of RC bridge columns in a computationally effective manner in order to avoid bridge failure during future earthquake events.

44. Numerical evaluation and design of bolted intermodular connection for high-rise mass timber modular buildings
Presenter: Juan S. Zambrano-Jaramillo, Oregon State University.
Topic Area: Structural Engineering 

Intermodular connections are required to assemble the volumetric modular units as part of the building's gravity system, to accommodate the building drifts, and to transfer the lateral loads through the diaphragm to the lateral force-resisting system. Considering that the stiffness and the location of the intermodular connections influence the diaphragm response of the buildings. This numerical study evaluates the translational and rotational stiffness of the intermodular connection based on two design configurations. To compare the performance of the established intermodular connections, 3D finite element models in Abaqus were developed for further validation with experimental tests. The configurations of the proposed connections were analyzed with varying bolt and steel plate sizes subjected to monotonic lateral load to study their shear and moment capacity. The numerical models were used to comprehensively analyze the connection components and their influence on the connection strength and capacity to accommodate the building drifts and transfer the lateral loads. The study showed that the connection capacity relies on the combined effect of shear and tension of the bolt elements and the shear strength of the mass timber columns. In addition, the study allowed the authors to better understand the expected behavior of the proposed connections before the experimental testing required for their calibration, based on the lack of details on mass timber intermodular connections. Finally, this study suggests recommendations for the connection design to perform the experimental testing based on the configuration that showed a better numerical performance in strength and deformation capacity.

45. Large-scale seismic testing of External Socket connections
Presenter: Julio A. Samayoa, NC State University. 
Topic Area: Structural Engineering 

Accelerated bridge construction (ABC) is gaining popularity worldwide due to its many benefits, including reduced total delivery time, minimized traffic impact, improved construction quality, and shorter on-site construction time. In seismic regions, one of the critical aspects of ABC is the design of the connections between the precast elements. As part of an ongoing research program at NC State, five large-scale specimens of RC column-to-cap-beam with external socket connections were tested under reverse cyclic conditions. External sockets offer significant advantages over internal sockets, particularly in reducing cap beam or foundation strain demands. The series of tests explored different socket heights while maintaining similar material strengths for the structural members and connections. In addition, advanced non-contact instrumentation techniques, such as digital image correlation and an optoelectronic measurement system, were used to measure the external socket's displacement fields and the column's strain demands. Results have shown that it is possible to achieve the performance of cast-in-place connections with different socket heights, considering specific conditions regarding the strength of the different components of the external connection. In conclusion, the results of large-scale tests represent an essential step forward in understanding the mechanics of external socket connections and could significantly improve ABC design, helping to create more efficient and effective connections for bridges.

46. Seismic hazard mitigation of tall buildings with mid-level isolation
Presenter: Konstantinos Kalfas, The University of Texas at Tyler.
Topic Area: Structural Engineering 

Mid-level seismic isolation has become a valuable solution for tall buildings to effectively separate the various parts having several functions, and thus different seismic performance requirements, with the main advantage being the interruption of the flux of energy between the upper and lower stories. The isolation layers that are introduced at various heights of the buildings may filter the inertial forces transmitted to the superstructure and improve the seismic behavior of the whole system. This paper studies a 20-floor building and several mid-story configurations where the isolation layer is located at several heights, in order to discuss the performances of each model and to assess the best location along the height of the structure. OpenSees is employed to calculate the high non-linearities of the models and to consider the interaction between the vertical loads and the horizontal forces. The various responses are discussed in terms of shear forces, accelerations and drifts, demonstrating the potentialities of inter-story isolation as a means of base isolation.

47. Shake Table Tests of Flexible Slide-Rocking Structures
Presenter: Mohammadreza Farooghi-Mehr, University of Nebraska-Lincoln.
Topic Area: Structural Engineering 

Freestanding structures are not attached to the ground or at their base and are free to slide, rock, and even overturn during seismic events. This class of structures includes classical columns, statue-pedestal systems, various mechanical and electrical components, certain types of bridge columns, and more. Analytical and experimental studies of rigid freestanding structures have highlighted the importance of friction at the base of the structure, and that sliding, and slide-rocking behavior have considerable impact on the rate of overturning. On the other hand, studies of flexible freestanding structures have emphasized that elastic and vibratory motion are non-negligible and similarly impact the rate of overturning, even for structures that would ordinarily be classified as rigid. Despite these observations, relatively little is known regarding the seismic performance and vulnerability of freestanding structures accounting for both structural deformation and sliding modes of response. To address this knowledge gap, an analytical and experimental campaign are ongoing to understand the role of material and geometric parameters on the seismic performance and vulnerability of these structures. To this end, this poster describes a full-scale shake table testing campaign in which a flexible steel tower was tested in multiple configurations to vary key parameters including the slenderness, rocking radius, natural frequency, and coefficient of friction. Each configuration was tested to approximately 100 earthquake records, including several tests of repeatability, as well as subjected to system identification and slow-pull tests. Results highlight that there is a change in modes of energy dissipation as a function of natural frequency and slenderness. Structures with lower natural frequencies were observed to display increased elastic behavior, as expected. This led to a reduction in overturning for taller structures, while this led to an increase in overturning for squatter structures.

48. Drift-based fragility curves for reinforced concrete structural walls prone to out-of-plane buckling
Presenter: Paul Acuna, North Carolina State University. 
Topic Area: Structural Engineering 

Reinforced concrete structural walls (RCSW) are commonly used in high-seismicity regions to provide lateral stiffness in medium to high-rise buildings. While RCSW have historically performed well, an unexpected failure mode was observed in recent major seismic events, such as the 2010 Chile and 2011 New Zealand earthquakes. In both cases, out-of-plane buckling instability near the base ends of the lowest-level walls was noted. This failure mode was first reported in 1985 as part of a lab experimental program. It motivated the generation of two phenomenological models to predict the likelihood of RCSW undergoing out-of-plane buckling instability. However, this failure mode was never seen on a real structure until the Chile and New Zealand earthquakes. New approaches were then developed to improve the prediction capacity of existing models. This study conducts a fragility analysis on 12 tested walls where out-of-plane buckling instability is the primary failure mode, identifying five damage states. Story drift was selected as the engineering demand parameter (EDP), and the resulting drift-based fragility curves offer valuable insights for designers and owners, aiding them in assessing the likelihood of RCSW failure due to out-of-plane buckling instability.

49. Cyclic load test of Cantilever Stiffened Buckling Restrained Brace with Low-yield Steel
Presenter: Young K. Ju, Korea University. 
Topic Area: Structural Engineering 

Framed structures are often vulnerable to damage caused by earthquakes, and one highly effective method used to mitigate such damage is the Buckling Restrained Braces (BRBs). BRBs can be divided into two main types: the concrete or mortar-filled BRB and the all-steel BRB. While the former requires curing time after filling and is more prone to developing voids, the latter has been favored by several studies due to its ability to handle deformation caused by tension and compression. However, controlling local buckling remains a significant challenge with all-steel BRBs. To address this issue, this study proposes a new type of BRB called the Cantilever Stiffened Buckling-Restrained Brace (CAS-BRB). This innovative design utilizes low-yield steel and a cantilever-type stiffener to ensure the tension length remains unaffected. The cantilever length does not occupy the displacement-bearing length during tensile loads, which reduces the core deformation rate. On the other hand, when a compression load is applied, the core experiences buckling, and the stiffener comes into contact to constrain local buckling and enhance rigidity. The CAS-BRB design has effectively mitigated damage caused by severe earthquakes and is a suitable alternative to the traditional all-steel BRB. The study aimed to develop a new BRB type that meets performance certification criteria while maintaining force stability and following the loading protocol of the American Institute of Steel Construction standard. Through experimentation, it was confirmed that the effectiveness of this innovative design is influenced by the cantilever length, which emphasizes its efficiency.

50. Assessing Structural Resilience to Tsunami Threats: Fragility Analysis and  Damage Control Limit States
Presenter: DoSoo Moon, University of Hawaii at Manoa.
Topic Area:Tsunamis

Tsunamis represent significant coastal threats, often causing extensive harm due to their infrequent occurrence. The precise assessment of these hazards is inherently challenging due to their rarity. While existing literature emphasizes the importance of sustainability and resilience in hazard planning, a notable gap exists in the availability of comprehensive fragility curves. This research, based on the guidelines provided by the American Society of Civil Engineers (ASCE 7), focuses on evaluating the structural resilience of a reinforced concrete building under the threat of tsunamis. Fragility curves are developed using various intensity measures over two tsunami cycles. Structural and reliability analyses are employed to estimate failure probabilities, and the impact of tsunamis on a model building is simulated through static pushover analysis, nonlinear static time history analysis, and nonlinear dynamic time history analysis to understand structural behavior. Additionally, the study includes an assessment of serviceability and damage control limit states. Fragility analysis, utilizing nonlinear dynamic time history and nonlinear regression techniques, is conducted to evaluate the structures vulnerability at various damage states, considering increasing inundation depths and flow velocities. The findings from static pushover and dynamic time history analyses effectively predict engineering demand parameters. This research underscores the importance of applying ASCE 7 guidelines to model the effects of tsunamis on critical infrastructure and assess their structural robustness. The resulting fragility curves provide valuable insights into how structures withstand varying tsunami intensities, with an added focus on servicability and damage control limit states. Furthermore, the study emphasizes the potential benefits of incorporating actual tsunami data, if available, in future research. This could significantly enhance hazard assessments and predictions, contributing to more informed decision-making in coastal planning and disaster management.