Post-earthquake Functionality Research Articles

Quantitative evaluation method for post-earthquake functionality loss of pedestrian flow pathways within a complex building using evacuation and rescue simulation

The complex building is a single building, characterized by its large size and complicated structural systems, such as high-rise-buildings, long-span-podium, and large underground space, as well as diverse functions. The pedestrian flow pathways within a complex building play a crucial role in urgent evacuation and rescue following seismic events. This study proposed a quantitative method for evaluating the functionality loss of pedestrian flow pathways within the complex building following seismic events. The method performed the component fragility analysis and constructed the speed reduction models that considered the variations of occupants' motions under different damage states of various nonstructural components. To evaluate the functionality loss of pedestrian flow pathways, the evacuation and rescue scenarios were established by analyzing the maximum speeds and behavioral delays of occupants at different spatial locations within the post-earthquake complex building. Based on the simulation, a quantitative index was constructed. Finally, a process accounting for uncertainties such as component damage was presented by generating the engineering demand parameters. A case study was employed to demonstrate the functionality loss of pedestrian flow pathways on each floor and in different areas within the post-earthquake complex building, which has reference significance for improving the post-earthquake complex building 's evacuation capacity as soon as possible to deal with secondary risk.

Multilevel assessment method for post-earthquake functionality of medical buildings considering component–department–floor interdependencies

The assessment of the post-earthquake functionality of medical buildings (PEFMB) is critical for the post-earthquake emergency response, recovery, and resilience-based seismic design of medical buildings. Hospitals are complex functional systems that exhibit multilevel functional coupling from components to departments to floors. Existing methods have challenges, including the difficulty of considering the impact of different departments located on different floors on medical functions, and a lack of multilevel performance improvement strategies for enhancing post-earthquake medical functionality. A multilevel assessment method for the PEFMB that considers component–department–floor interdependencies (CDFI) was developed in this study. This method establishes a functional logical relationship between components and departments using fault tree models of typical departments. A multilevel functional coupling relationship among the components, departments, and floors was established by incorporating floor nodes to reflect the impact of departments located on different floors. This enabled the assessment of the PEFMB considering the CDFI. Furthermore, methods for identifying critical failure paths in the PEFMB were developed, and multilevel performance improvement strategies by adjusting medical equipment and departments along the critical failure path were recommended. The proposed method is demonstrated using an outpatient building. The main conclusions are as follows. (1) The proposed multilevel assessment method enables quantitative assessment of the PEFMB and exhibits good scalability. (2) This method provides a clear and intuitive visualization of the critical failure path in healthcare functionality under seismic conditions. The proposed multilevel improvement strategies can enhance the post-earthquake functionality of medical buildings at multiple levels, which provides a valuable reference for the seismic design of medical buildings.

A Novel Technique for Improving Cyclic Behavior of Steel Connections Equipped with Smart Memory Alloys.

Residual drifts are an important measure of post-earthquake functionality in bridges and buildings, and can determine whether the structure remains fit for its intended purpose or not. This study aims at investigating numerically, through finite element (FE) analysis in ABAQUS, the cyclic response of exterior steel I beam-hollow column connection using welded shape memory alloys (SMA) bolts and seat angles. This is followed by validating the numerical model using an accredited experimental data available in the literature through different techniques, (1) SMA bolts, (2) SMA angles, (3) SMA bolts and angles. The parameters investigated included: SMA type, SMA angle thickness, SMA bolt diameter, SMA angle stiffener and SMA angle direction. The cyclic performance of the steel connection was enhanced further by varying the bolt diameter, plate thickness, angle type and direction. The results revealed that the connections equipped with a combination of SMA plates and SMA angles reduced the residual drift by up to 94%, and doubled the self-centering capability compared to conventional steel connections. Moreover, the parametric analysis showed that Fe-based SMA members could be a good alternative to NiTi based SMA members for improving the self-centering capability and reducing the residual drifts of conventional steel connections.

Post-earthquake building services downtime distribution: a case study of the 2016 Kumamoto, Japan, earthquake

AbstractSeismic damage to building services systems, that is, mechanical, electrical, and plumbing systems in buildings related to energy and indoor environments, affects the functionality of buildings. Assessing post-earthquake functionality is useful for enhancing the seismic resilience of buildings via improved design. Such assessments require a model for predicting the time required to restore building services. This study analyzes the downtime data for 250 instances of damage to building services components caused by the 2016 Kumamoto earthquake in Japan, presumably obtained from buildings with minor or no structural damage. The objectives of this study are (1) to determine the empirical downtime distribution of building services components and (2) to assess the dependence of the downtime on explanatory variables. A survival analysis, which is a statistical technique for analyzing time-to-event data, reveals that (1) the median downtime of building services components was 90 days and, 7 months after the earthquake, the empirical non-restoration probability was approximately 32%, (2) the services type and the building use are explanatory variables having a statistically significant effect on the downtime of building services components, (3) the log-logistic regression model reasonably captures the trend of the restoration of building services components, (4) medical and welfare facilities and hotels restored building services components relatively quickly, and (5) the 7-month restoration probability was observed to be highest for electrical systems, followed by sanitary systems, then heating, ventilation, and air conditioning systems, and finally life safety systems. These results provide useful information to support the resilience-based seismic design of buildings.

A genetic algorithm framework for seismic retrofit of building portfolios to enhance community resilience

Earthquakes can impose significant human, societal, and economic burdens, emphasizing the necessity of community preparedness, including mitigation. Seismic retrofitting, a key preparedness measure, seeks to enhance structural resilience against earthquakes. Despite the effectiveness of community-level plans, challenges persist in quantifying their effectiveness and optimizing resource allocation. To address these challenges, this paper introduces a genetic algorithm (GA) framework designed to optimize seismic retrofitting of building portfolios in communities, aiming at achieving community-level resilience goals. The proposed framework, part of a simulation-based approach, probabilistically models building damage and post-earthquake functionality of the community. It calculates seismic retrofit levels (in terms of percentage shift in the median of fragility curves) for each building archetype, considering different shifts in the damage fragility curves and the percentage of retrofitted buildings for each retrofit level. The optimization problem maximizes average post-earthquake functionality, constrained by available community funds. The proposed GA framework is illustrated using the real-world example of Salt Lake City, Utah, in collaboration with the NIST Center for Risk-based Community Resilience Planning, showcasing its application through the Interdependent Networked Community Resilience Modeling Environment (IN-CORE). The results of the considered illustrative example reveal substantial improvements in community functionality under different budget scenarios and retrofit levels. The GA framework represents a significant advancement in supporting informed decisions for community resilience. Community leaders can use its outputs to make informed decisions, considering specific factors and trade-offs between benefits and costs.

Seismic resilience evaluation of granular column-supported road embankments on liquefiable soils

In this study, the seismic resilience of granular column-supported road embankments on liquefiable soils is examined to enhance the understanding and seismic design of resilient transportation infrastructure. A nonlinear dynamic analysis of embankments on liquefiable soils is performed, and the results are validated against centrifuge test data. In the assessment, a functional analysis framework encompassing fragility, vulnerability, and restoration functions is employed to evaluate the robustness and recovery of embankments. The resilience of embankments is quantified by the comprehensive life-cycle resilience index (R), which considers various factors, such as the embankment height, the liquefiable soil thickness, and the area replacement ratio (AR) of granular columns. A simplified design method is proposed that involves a model for rapidly assessing the resilience state of embankments under varying seismic intensities. The analysis highlights the essential role of granular columns in mitigating liquefaction-induced damage during seismic events, improving robustness, and recovering post-earthquake functionality, and a practical and reliable tool is developed for assessing embankment resilience across diverse seismic scenarios.

A novel method for post-earthquake functional evaluation of city building portfolios

Enhancing the seismic resilience of city building portfolios is crucial to mitigating the impact of seismic disasters. A novel method is proposed to evaluate the post-earthquake functionality of city building portfolios, which can serve as the foundation for assessing the seismic resilience of cities. This method incorporates multiple dimensions of functional evaluation, ranging from structural and nonstructural components to city building portfolios, elucidating the mechanism of functional assemblies from lower to higher dimensions. The calculation of the physical functionality of individual buildings relies on the functionalities of their structural and nonstructural components, which are determined using the functional mapping method. The impacts of infrastructure failures on the functionality of individual buildings are explored using the hierarchical belief rule base inference method based on the evidential reasoning algorithm (BRBI-ER). A technique that combines Point of Interest analysis and visual interpretation is utilized to classify building portfolios into three types: single-function building portfolios, multi-function building portfolios, and integrated-function building portfolios. A cumulative functional correlation model and an integrated functional correlation model using BRBI-ER are established to evaluate the functionality of these types of building portfolios. The results can contribute to predicting the risk of functional losses before earthquakes, guiding the recovery process after earthquakes, and taking proactive measures to improve the seismic resilience of cities.

Shaking table tests of power distribution cabinets: Physical damage, post-earthquake functionality and seismic response evaluation

Power distribution cabinets (PDCs) are widely used in several critical facilities to ensure the power supply and distribution. Although these cabinets may suffer seismic damage during earthquakes, and result in cascading functionality, economic and life losses, they have received little attention in terms of seismic performance. Therefore, there is an increasing need to understand the performance of such equipment during earthquakes. This study conducted shaking table tests on three PDCs to investigate the seismic performance and dynamic responses. Both physical damage and post-earthquake functionality evaluation were conducted during shaking table tests. The seismic responses of tested cabinets including natural frequency, stress, acceleration, and deformation responses were presented in detail. Seismic qualification levels of tested cabinets based on existing rules were also introduced. This paper not only enlarges the experimental database of the seismic performance of PDCs, but also provides basic data and rules for performance-based seismic evaluation of such nonstructural components.

Dead people aren’t resilient

Resilience, achieving rapid recovery so that society can bounce back from a disaster, is a desirable goal, but sometimes the focus should be only on safety. The 2023 Turkey/Syria earthquake illustrates the case where limited resources should be prioritized on safety, that is, the collapse prevention performance objective, rather than the significantly more expensive goal of post-earthquake functionality.

Implications of 5G rollout on post-earthquake functionality of regional telecommunication infrastructure

Telecommunication infrastructure (TI) is becoming increasingly vital in modern society, where information exchange is needed in almost all aspects of the built environment, business operations, and people's daily lives. The ongoing 5G rollout will lead to a paradigm shift in regional TI deployment landscape, with increased seismic hazard exposure particularly due to the densely deployed small cells. As TI is known to be vulnerable to seismic hazard impacts yet necessary for post-earthquake emergency response, this study carries out a pioneering effort in quantifying the post-earthquake TI failures and functionality to better support risk mitigation decision-making. We propose a novel seismic risk assessment framework for regional 5G TI, by holistically integrating regional seismic hazard analysis, infrastructure seismic exposure data, electric power infrastructure seismic fragility modeling and network connectivity analysis, as well as wireless TI functionality modeling. The proposed framework is evaluated based on a hypothetical regional infrastructure testbed located in Memphis, Tennessee, subjected to several earthquake scenarios. From a reference heterogeneous 5G TI deployment scenario, the results indicate that significant performance degradation of 5G TI is expected especially after major earthquake events. Enabled by the proposed framework, we further compared the efficacy of several risk mitigation strategies and pertinent implications are provided.

Seismic Performance of U-Shaped Connection for Prefabricated Steel Plate Shear Wall

In this investigation, a U-shaped connection (U-C) was introduced for a prefabricated steel plate shear wall with beam-only connections. This design replaces a portion of shear bolts with tension bolts to enhance bolt efficiency and reduce the overall bolt count, and it is suitable for a prefabricated high-rise steel structure. Four 1/3 scale specimens were designed, and an array of performance aspects including failure modes, hysteretic behavior, skeleton curves, energy dissipation capacity, stiffness degradation, and key performance indicators were systematically investigated through a combination of quasi-static tests and finite element analyses. The results showed that the combination arrangement of tensile and shear bolts in U-C effectively reduced the usage of bolts used and reduced installation costs; under low cycle reciprocating loads, the ultimate bearing capacity and energy dissipation capacity of a beam-only-connected prefabricated steel plate shear wall with U-shaped connection (BPSW-U) had slightly decreased compared with the prefabricated steel plate shear wall with discontinuous cover-plate connection (DCPC). Nevertheless, the BPSW-U excelled in preserving the integrity of the frame beams, channeling structural plastic deformations primarily into the infilled steel plate. This design feature ensures that post-earthquake functionality recovery can be achieved by simply replacing the infilled steel plate.

Post-earthquake functionality assessment for urban subway systems: Incorporating the combined effects of seismic performance of structural and non-structural systems and functional interdependencies

Post-earthquake functionality assessment for urban subway systems: Incorporating the combined effects of seismic performance of structural and non-structural systems and functional interdependencies

Seismic behaviors of self-centering steel structural joints with phased energy dissipation

To reduce residual deformation in steel moment-resisting frames under seismic actions and facilitate rapid post-earthquake functionality recovery, a self-centering steel structural joint with phased energy dissipation was proposed. This joint achieves self-centering capability through the restorative force provided by prestressing steel strands. Additionally, it employs two energy dissipation mechanisms, namely frictional sliding between the friction plate and the T-stub web and the plastic deformation of the T-stub itself, at different stages to dissipate seismic energy. This approach enables effective phased energy dissipation. Cyclic loading tests were conducted on four full-scale specimens with varying initial prestressing forces of steel strands and bolt pretension. This study obtained seismic performance parameters of the specimens, including hysteretic curves, skeleton curves, stiffness degradation, and energy dissipation. Furthermore, the phased energy dissipation mechanisms of these specimens at different loading stages were investigated. It was found that the loading process of the specimens could be divided into three stages: elastic stage, sliding stage, and strengthening stage. During the elastic stage, the specimens remained closed, with all components in an elastic state. As the loading progressed to the sliding stage, the specimens dissipated energy through frictional sliding between the friction plate and the T-stub web. In the strengthening stage, the primary energy dissipation mechanism of the specimens was the plastic deformation of the T-stub. Moreover, the initial prestressing force of the steel strands had significant influence on the bending capacity and self-centering capability, while the bolt pretension mainly affected the energy dissipation capacity and bending capacity of the specimens.

Damage classification after the 2009 L’Aquila earthquake using multinomial logistic regression and neural networks

Post-earthquake surveys represent a fundamental tool for managing the emergency phase after a strong earthquake. In Italy, the evaluation of the post-earthquake functionality of ordinary buildings is based on the AeDES forms (Agibilitá e Danno nell’Emergenza Sismica, or equivalently, Rapid Post-Earthquake Damage evaluation forms). This form includes information on the building and records of the observed damage classified according to type and intensity in 60 subclasses. Based on the observed damage and expert judgment, the buildings are clustered into six risk classes, from A to F. The assigned class is used to calculate the maximum economic reimbursement owed for the reconstruction or repair of the building. However, often the cluster assignment is not entirely objective due to the inherent responsibility associated with a less conservative assessment. This paper uses the data from the 2009 L’Aquila earthquake to develop classification models based on multinomial logistic regression (MLR) and artificial neural networks (ANN) calibrated with data theoretically less influenced by personal biases. The proposed models, particularly the MLR, are intended to support the decision-making of the evaluation team in future updates of the AeDES forms. This approach cannot substitute expert evaluation, which is always necessary for complex scenarios but may mitigate the impact of subjectivity and can provide an indication of the expected outcome of the survey.

A Quantitative Evaluation Model for the Seismic Resilience of Water Supply Systems Based on Fragility Analysis

A quantitative evaluation model is proposed to assess the seismic resilience of water supply systems. The water supply system is divided into three parts: water sources, aboveground infrastructures, and underground pipeline network, and importance factors for the different parts are quantified. Resilience demand is expressed as the desirable functionality loss and the recovery time of the water supply system after an earthquake. First, seismic fragility models are established for the different components of the water supply system. A water quality index is utilized to represent the impact of earthquakes on the water sources, the seismic performances of aboveground infrastructures are represented by fragility curves, and the repair rate in terms of number of repairs per kilometer is adopted for the pipeline network. Then, the post-earthquake functionality of the water supply system is quantified based on seismic fragility analysis. Changes in the water quality index are used to indicate the functionality losses related to water sources, the functionality losses of aboveground infrastructures are represented by the economic losses derived from component fragility curves, and post-earthquake functionality losses in the underground pipeline network are quantified by hydraulic simulations. The functionalities of the three parts are calculated separately, and then the overall system functionalities are obtained as the sum of the weighted functionalities of the three parts. Finally, a repair strategy is developed and the recovery time is calculated considering the system damage scenarios, system functionality analyses, and resource reserves. The proposed resilience assessment model considers all components of the water supply system, and the results are reliable when the basic information is complete and accurate.

SEISMIC RETROFIT OF SUBSTANDARD RC BRIDGES USING CONTEMPORARY MITIGATION MEASURES

As essential infrastructure components, existing substandard bridges may cause significant economic losses at the urban scale as they are prone to different damage modes under seismic excitations. Due to the large number of existing RC bridges in earthquake-prone regions and the continuous updates in seismic design criteria, there is increasing interest in developing effective seismic retrofit techniques for enhancing the performance of these structures. This study thus investigates the effectiveness of contemporary retrofit measures for upgrading the seismic performance of RC bridges, namely ultra-high-performance concrete (UHPC) jackets and self-centering energy dissipating (SCED) braces. Detailed fiber-based numerical models are developed for scaled RC bridge substructures retrofitted with the adopted mitigation measures. The hysteretic behavior of the bridge substructures from quasi-static cyclic loading experiments conducted in previous studies is utilized to verify the developed fiber-based models. The validated modeling approaches of retrofit strategies are then applied to an old benchmark bridge located in a medium seismicity zone. The inelastic response of the benchmark bridge substructure before and after the retrofit with different mitigation measures is assessed using the verified fiber-based numerical models. The results demonstrate that the retrofit measures increased the lateral strength of the bridge bent by 37.5%. Also, 10% improved ductility was observed in the UHPC retrofitted bent. This performance assessment study enabled the selection of effective measures to mitigate the vulnerability of substandard bridge members to ensure their post-earthquake functionality.

Seismic resilience assessment of bridges considering both maximum and residual displacements

The residual displacement of the bridge column has a great influence on evaluating earthquake damage and seismic resilience of bridges. However, the residual displacement is rarely considered when assessing post-earthquake functionality and seismic resilience of bridges. An evaluation method for seismic damage of bridges is proposed in this paper by introducing both the maximum drift (MD) and residual drift (RD) of the bridge column as engineering demand parameters. The damage states and damage probability of bridges under earthquakes are determined through the joint probability density function and used to evaluate the functionality loss and recovery of bridges after earthquakes. A seismic resilience assessment framework of bridges considering both MD and RD is proposed and applied to assess the seismic resilience of a two-span reinforced concrete (RC) bridge. The results indicate that RD greatly impacts the probability of collapse damage of bridges. The evaluated functionality loss of the bridge considering both MD and RD is larger than that considering the single MD index after the earthquake. When both MD and RD are taken into consideration, the evaluated seismic resilience is smaller than the result considering the single MD index. The maximum reduction of seismic resilience is 14.1% at the peak ground acceleration (PGA) of 0.7 g. With the increase of PGA, the seismic resilience considering both MD and RD is similar to that only considering MD. The seismic resilience can be overestimated when RD is not taken into consideration.

Post-earthquake functionality assessment of MRFs enhanced by resiliently lateral-resistant and bottom systems

The accumulated stiffness and strength degeneration of rigid bottom joints and uneven lateral deformation mode of the moment-resisting frame (MRF) during earthquakes can result in disastrous structural failures. Damage accumulation, excessive residual inter-story drift, and the lack of self-centering behavior and energy-dissipation capacity in structures are major challenges in controlling losses after earthquakes. This paper aims to propose a self-centering energy-dissipation (SCED) system that enhances the seismic performance of MRFs. This system, called the resilience-enhanced MRF (ReMRF), utilizes a rocking truss as a lateral-resistant structure and incorporates two bottom joints with SCED capabilities into the MRF design. These bottom joints, referred to as the Buckling Restraint Steel Plate (BRSP) bottom joint and the Light Self-Centering (LSC) bottom joint, are composed of key components such as BRSPs and post-tensioned (PT) strands, respectively. Structural design methods and parameters for the rocking truss and bottom joints are discussed to determine optimal values for balancing stiffness demand, SCED capacity, and construction convenience. Special attention is paid to the working stability of the bottom joints during earthquakes and the effectiveness of the SCED system. Results indicate that the performance of the bottom joints and the SCED system is in line with expectations. The findings from both pushover and time history analyses have substantiated that ReMRF outperforms MRF in terms of achieving higher seismic performance objectives. It is intuitively demonstrated by several quantitative metrics derived from static and dynamic analyses, including the overstrength factor, ductility factor, drift concentration factor, peak inter-story drift, and residual inter-story drift.

Scenario-based earthquake damage assessment of highway bridge networks

In earthquake-prone regions, the evaluation of seismic impacts on bridges is crucial to mitigation, emergency, and recovery planning for highway networks. The degree of bridge damage determines the cost and time required for repairs and the level of post-earthquake functionality including disruption of transportation network, increased costs due to reduction of traffic flow and restricted access to emergency routes. The article presents the methodological development and implementation of an interactive web application for rapid geospatial assessment and visualisation of earthquake damage scenarios of municipal highway bridge networks based on open access datasets. The proposed framework consists of the following successive models: hazard, inventory, damage, and impact. The seismic hazard model generates spatial distribution of the shaking intensity for earthquake scenarios in terms of ground motion intensity measure using ground motion prediction equations based on seismic hazard model for Eastern Canada. The shaking intensities are then modified with local site amplification factors based on the Canadian highway bridge design code values. The inventory model provides a database of existing bridges based on open-access data which are then classified according to their seismic vulnerability. The damage model assesses seismic performance of classes of bridges by applying respective fragility functions represented as probabilistic relationships between the intensity measure and the degree of expected damage. The impact model evaluates the post-earthquake traffic-carrying capacity of the highway network based on the predicted damage including repair cost as a percentage of replacement cost of bridges and inspection priority. The web-application is demonstrated with a bridge network in Quebec City including 117 bridges subjected to 180 earthquake scenarios. The proposed methodology is particularly useful to facilitate direct communication of potential impacts to emergency managers and city transport officials.

Assessing the Seismic Demands on Non-Structural Components Attached to Reinforced Concrete Frames

Nonstructural components (NSCs) are the systems that are attached to the floors of a building structure. NSCs have become critical in sustaining post-earthquake functionality while constructing seismic-resilient structures. The seismic behavior of the NSCs primarily depends upon the behavior of the structure to which the NSC is attached. Building structures are subjected to earthquake loads and behave differently when the supporting soil type varies. In light of this, this study investigates the seismic demands on NSC attached to the floors of an elastic-reinforced concrete building frame supported by different soil types. The present study considered a regular building frame and a building frame with mass irregularity on the lower story. A total of 3 sets of 11 horizontal spectral-matched ground motions consistent with each soil type are considered. Floor response spectra (FRS) can be used to measure the seismic load on non-structural components. Primarily, it was found that the ordinates of FRS depend on the floor height, the vibration periods of the building, and the soil type. The presence of mass irregularity at the lower story amplified the floor response at all floor levels. Additionally, the values of floor spectral acceleration increase as soil flexibility increases. The amplification factors are critical for generating the floor response spectra, and their variation along the building height is discussed. The floor acceleration was found to vary non-linearly with the height of the building. Finally, artificial neural networks (ANNs) are employed to develop the prediction models for dynamic amplification factors. The results calculated by the dynamic time history analyses are utilized to validate the proposed prediction models.