AbstractA spectrum of simplified methods for estimating building seismic drift demands is conceptualized. On one extreme are mechanics-based approaches that are derived solely from fundamental ...engineering principles. On the other end are purely data-driven models that are developed using parametric data sets generated from nonlinear response history analyses. Between these two extremes, there are models that combine elements of basic engineering principles and statistical learning (hybrid models). First, the benefits and drawbacks of four existing simplified seismic response estimation methodologies that fall within this spectrum of approaches are critically examined. Subsequently, a generalized framework for developing and validating hybrid and/or purely data-driven seismic demand estimation models is proposed. Using this framework, two new machine learning–based models are developed and rigorously evaluated. Finally, a comparative assessment of the existing and newly developed models is conducted while focusing on their predictive performance and the level of effort needed to implement them.
•A framework for assessing the post-earthquake structural safety of damaged buildings is presented.•The concepts of response and damage patterns are introduced and incorporated into a systematic ...methodology integrating probabilistic seismic demand analysis, component-level damage simulation and robust assessments of the residual collapse capacity.•Machine learning algorithms are used to explicitly link the response and damage patterns to residual collapse capacity of a damaged structure, and are able to probabilistically predict the structural safety states given any available information.•A series of predictive models including Classification and Regression Trees and Random Forests are developed and examined in detail to achieve the optimal model which balance multiple performance measurements.•In contrast to previously judgement-based methods for the tagging process, this innovative approach provides a solid statistical support for structural safety assessment.•High prediction accuracies are observed based on either response and damage patterns.
A machine learning framework is presented to assess post-earthquake structural safety. The concepts of response and damage patterns are introduced and incorporated into a systematic methodology for generating a robust dataset for any damaged building. Incremental dynamic analysis using sequential ground motions is used to evaluate the residual collapse capacity of the damaged structure. Machine learning algorithms are used to map response and damage patterns to the structural safety state (safe or unsafe to occupy) of the building based on an acceptable threshold of residual collapse capacity. Predictive models including classification and regression tree and Random Forests are used to probabilistically identify the structural safety state of an earthquake-damaged building. The proposed framework is applied to a 4-story reinforced concrete special moment frame building. Distinct yet partially overlapping response and damage patterns are found for the damaged building classified as safe and unsafe. High prediction accuracies of 91% and 88% are achieved when the safety state is assessed using response and damage patterns respectively. The proposed framework could be used to rapidly evaluate whether a damaged building remains structurally safe to occupy after a seismic event and can be implemented as a subroutine in community resilience evaluation or building lifecycle performance assessment and optimization.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK, ZRSKP
Summary
Aftershocks have been shown to exacerbate earthquake‐induced financial losses by causing further damage to structural and nonstructural components in buildings that have already been affected ...by a mainshock event and increasing the duration of disrupted functionality. Whereas seismic loss assessment under isolated events has been addressed thoroughly in previous studies, comparatively less has been accomplished in the area of loss assessment under sequences of mainshock‐aftershock ground motions. The main objective of the current study is to formulate a comprehensive framework for quantifying financial losses under sequential seismic events. The proposed framework is capable of accounting for the uncertainties in the state of structure due to accumulation of earthquake‐induced damage, the time‐dependent nature of seismic hazard in the post‐mainshock environment, and the uncertainties in the occurrence of mainshock and aftershock events. Application of the proposed framework to a 4‐story reinforced concrete moment frame shows that consideration of aftershocks could increase lifecycle earthquake‐induced losses by up to 30% compared with mainshock‐only assessments.
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BFBNIB, FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SAZU, SBCE, SBMB, UL, UM, UPUK
The increase in seismic activity after a large-magnitude earthquake coupled with the reduction in the lateral load-carrying capacity of the affected structures presents a significant human and ...financial risk to communities. The focus of this paper is placed on quantifying the impact of both the elevated post-mainshock seismic hazard as well as the mainshock-induced structural damage on the seismic risk of three reinforced concrete moment frame structures. The seismic hazard due to sequential earthquakes is examined in both pre- and post-mainshock environments. The time-dependent nature of seismic hazard in the post-mainshock environment is accounted for through the adoption of a Markov risk assessment framework. In the post-mainshock environment, the seismic risk is examined as a function of the time elapsed since the mainshock’s occurrence while in the pre-mainshock environment, the risk is investigated during an assumed lifespan of 50 years for the studied structures. For the buildings and the high-seismicity site used in this study, both the increased post-mainshock seismic hazard as well as the reduction in the structural capacity are found to have a great influence on the seismic risk. The substantial contribution of aftershocks to the collapse risk in the pre-mainshock environment highlights the need for a design procedure that accounts for the additional seismic risk from aftershocks.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK, ZRSKP
Tuned mass dampers (TMDs) are widely implemented in many types of structures, such as tall buildings, wind turbines, towers, and bridges, to enhance the structural performance subjected to seismic ...and wind loading. In the present study, we aim to comprehensively investigate the effectiveness of TMD, by performing seismic vulnerability assessment of a 20-story steel building equipped with TMD and considering the soil-structure interaction (SSI) effects. A suite of high-fidelity three-dimensional nonlinear finite element simulations—in which nonlinear constitutive models are adopted for both structural components and soil, and Domain Reduction Method (DRM) and Perfectly Matched Layer (PML) are utilized to inject the seismic ground motions and represent the semi-infinite contents of the soil media, respectively—are conducted to obtain the structural responses. Finally, the performance of TMD is examined by comparing the fragility curves obtained under different conditions, i.e., with and without TMD, with and without SSI. It is observed that the TMD can notably decrease the structural demands, while the SSI effects can increase the fragility of structures, especially under strong earthquakes.
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EMUNI, FIS, FZAB, GEOZS, GIS, IJS, IMTLJ, KILJ, KISLJ, MFDPS, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, SBMB, SBNM, UKNU, UL, UM, UPUK, VKSCE, ZAGLJ
•A Markov framework for seismic risk assessment under mainshock-aftershock sequences.•Mainshock versus mainshock-aftershock lifecycle seismic risk and loss.•Comparison between mainshock versus ...aftershock loss due to a hypothetical magnitude 7 event.
A framework for building-portfolio risk and loss assessment under mainshock-aftershock earthquake sequences is presented. The temporary increase in seismic hazard after a large-magnitude mainshock coupled with the reduction in the structural capacity under sequential ground motions are considered in the framework. For the inventory of reinforced concrete frames located in Los Angeles County, the annual rate of “complete” (HAZUS) damage and expected annual losses are, on average, 10% and 25% higher, respectively, when aftershocks are incorporated in the risk assessment procedure. A short-term risk and loss analysis after a hypothetical scenario mainshock on the Puente Hills fault showed a substantial increase in the seismic risk within one week after the mainshock. The aftershock-induced losses during the same period were estimated at approximately 30% of the losses due to the mainshock.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
•The seismic performance evaluation steps of FEMA P-58 have been applied to 15 RC frames.•The collapse risk and human and monetary consequences have been evaluated.•The effects of ductility, ...seismicity, height and redundancy have been investigated.•A thorough discussion on the reasons of variations is provided.
The main objective of this study is to employ performance-based earthquake engineering procedure to evaluate earthquake-induced risks in modern code-conforming reinforced (RC) concrete moment frames in terms of collapse risk and possible human and financial losses. A set of 30 archetype RC moment frames, designed based on the ASCE 7-05 and ACI 318-05 requirements, is selected for the evaluation purpose. The buildings are classified into 4-, 8- and 12-story and are designed with different levels of structural system ductility. The archetypes are assumed to be located in three zones with low, moderate and high levels of seismic hazard. The findings of the collapse assessment procedure indicate that the seismicity of the location significantly affects the collapse performance and the ductility, as long as the structure conforms to the requirements of modern design codes, has the least influence on the collapse risk. Also, it has been found that the expected annual repair costs lie in an interval with the minimum and maximum of 0.02% and 1.5% of the replacement cost and expected annual number of deaths ranges from 2×10−4% to 29×10−3% of the total occupants with the buildings located in the low seismicity zone having the minimum amounts of losses. Sensitivity analysis is employed to study the variations of earthquake consequences due to the variations in the design decisions.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK
AbstractEarthquake engineers lack well-founded consensus guidelines for selecting ground motion time series for sequential mainshock-aftershock events for use in seismic performance assessment. Past ...practice has seen sequences formed by coupling as-recorded mainshock and aftershock records and by using repeated mainshock records for both event types. Using mainshock-mainshock versus mainshock-aftershock record pairs, this paper assesses the structural performance of five ductile reinforced concrete frames with varying heights using sequential nonlinear response history analyses. Systematic differences are found in the frequency content of mainshock and aftershock records, which in turn produce expected differences in structural responses conditional on the dynamic characteristics of each structure. The outcome is measurable differences in the structural response, with mainshock-mainshock sequences potentially overestimating or underestimating seismic demand and risk relative to the use of more-appropriate mainshock-aftershock record pairs. This finding holds true even when mainshock-mainshock sequences are formed by preserving the magnitude and distance relationships between as-recorded mainshocks and aftershocks. The correlation between event terms of mainshock and aftershock ground motions recorded from the same sequence is found to have a significant impact on maximum story drift ratio. This paper provides recommendations for aftershock record selection that draw upon these results.
A number of simplified methodologies have been developed and used to estimate seismic drift demands in buildings. However, none of them have been systematically tested against a large number of ...buildings subjected to a diverse set of ground motions. This is partly attributed to the lack of existing databases of building designs, nonlinear structural models, and simulated seismic responses. This article introduces the development of a comprehensive database, which includes 621 special steel moment-resisting frames designed in accordance with modern codes and standards and their corresponding nonlinear structural models and seismic responses (i.e. peak story drifts, peak floor accelerations, and residual story drifts). The seismic responses for a subgroup of 100 steel moment-resisting frames subjected to three groups of site-specific ground motions (with 40 records each), at the service-level, design-based, and maximum considered earthquakes, are also included. The database has been utilized by the authors (in a separate study) to evaluate the performance of existing methods and develop data-driven and hybrid (combination of mechanics-based and data-driven) models for estimating seismic structural drift demands. The database can also be utilized in the development and implementation of a performance-based analytics-driven seismic design methodology.
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NUK, OILJ, SAZU, UKNU, UL, UM, UPUK
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