Summary
Reinforced concrete (RC) shear wall buildings with unreinforced masonry (URM) infilled moment frames are common in India and neighboring countries. This study assesses the influence of the ...URM infills on their seismic performance. Fully infilled, open first‐storied, and bare frame versions of a 25‐story shear wall building are considered. Multiple stripe analysis is conducted at five return periods to estimate their performance. Fragility functions for the collapse prevention limit state, which is based on seven engineering demand parameter exceedance thresholds, are generated and compared. The presence of infills (full or partial) is observed to have an overall positive effect on the performance of the RC frame‐shear wall buildings. The performance of the open first‐story building was comparable to that of the fully infilled building. The ratio of story shear carried by the moment frames and shear walls is studied at all return periods to understand the variation in frame shear wall interaction with increased damage for each building. In the case of buildings with infills, the frames carry a higher proportion of story shear at lower return periods. For all three buildings, the fraction of story shear carried by moment frames increases along the height of the building.
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FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SBCE, SBMB, UL, UM, 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.
The efficacy of various types of intervention measures intended to facilitate post-earthquake housing recovery can be evaluated ahead of time by using simulation models to quantify their benefits and ...tradeoffs. Towards this end, this paper presents a conceptual framework comprised of three components for modeling post-earthquake housing recovery. The modeling framework starts with a probabilistic assessment of building-level damage using recovery-based limit states that characterize post-earthquake functionality, inhabitability, and repairability. These limit states are the basis for the second component, which includes two different utility-based models for representing post-earthquake household decision making. Stochastic models to probabilistically quantify building-level recovery trajectories comprise the third and final component of the framework. Collectively, these alternative models can integrate the effect of building states, available resources, household decisions, and endogenous factors such as lifeline restoration. The modeling framework can be scaled to model spatiotemporal scenarios of housing recovery to inform jurisdictional-level policies, plans, and interventions to increase residential community resilience.
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NUK, OILJ, SAZU, UKNU, UL, UM, UPUK
•Multiscale cost-benefit analysis performed for Los Angeles Soft-Story Ordinance.•Implemented intensity- and time-based assessment for individual buildings.•Portfolio-scale cost-benefit evaluation ...conducted for hypothetical M 7.1 Puente Hills event.•Stochastic-event-set-based assessment performed at the portfolio scale.
A multi-scale (building-specific and portfolio) cost-benefit analysis of the Los Angeles soft-story Ordinance for woodframe residential buildings is presented. Building-specific loss functions (shaking intensity versus loss ratio) are computed by implementing the FEMA P-58 seismic loss assessment methodology on a set of archetype buildings that reflect the variations in key structural characteristics (e.g. 1st story wall layout, number of stories) of the approximately 12,000 buildings affected by the Ordinance. The cost-benefit ratio is assessed as the retrofit cost divided by the reduction in earthquake-induced losses that result from the retrofit. At the individual building level, both intensity and time-based cost-benefit assessments are performed. The latter uses the expected annual losses to determine the break-even time, which is the duration needed to recoup the upfront cost of the retrofit. The average break-even time when considering all archetypes is four to five years. At the portfolio-scale, an average cost-benefit ratio of 0.32 is obtained for a hypothetical Mw 7.1 Puente Hills scenario earthquake. A first-of-its kind stochastic event-set cost-benefit assessment is also performed, where all events (approximately 8000) that are significant to the region are considered. From this assessment, it was determined that the probability of achieving a desirable cost-benefit ratio (value between 0.0 and 1.0) within a 50-year period is approximately 0.9.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
Post-earthquake recovery models can be used as decision support tools for pre-event planning. However, due to a lack of available data, there have been very few opportunities to validate and/or ...calibrate these models. This paper describes the use of building damage, permitting, and repair data from the 2014 South Napa Earthquake to evaluate a stochastic process post-earthquake recovery model. Damage data were obtained for 1,470 buildings, and permitting and repair time data were obtained for a subset (456) of those buildings. A "blind" prediction is shown to adequately capture the shape of the recovery trajectory despite overpredicting the overall pace of the recovery. Using the mean time to permit and repair time from the acquired data set significantly improves the accuracy of the recovery prediction. A generalized model is formulated by establishing statistical relationships between key time parameters and endogenous and exogenous factors that have been shown to influence the pace of recovery.
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NUK, OILJ, SAZU, UKNU, UL, UM, UPUK
Surrogate models are growing in popularity within the earthquake engineering community because of their ability to increase the efficiency of computationally intensive tasks. This article examines ...the design of computer experiments (DoCE) for the purpose of developing seismic surrogate models. Two categories of DoCE approaches are discussed while underscoring the benefits and drawbacks of specific methods. Further insight is provided through an illustrative case study that develops surrogate models to predict the median collapse capacity and expected annual losses in single-family woodframe buildings with cripple walls. The implications of the chosen DoCE method on the predictive performance and efficiency (in terms of the required number of explicit simulations) of the associated surrogate models are closely examined. The results show that both factorial and Latin hypercube designs (LHDs) do not perform well when different approaches are used to generate the training and testing sets (i.e. out-of-design-type testing). An efficient hybrid design that combines an orthogonal array-based composite design with a small number of LHD samples is shown to produce a surrogate model with superior predictive performance.
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NUK, OILJ, SAZU, UKNU, UL, UM, UPUK
A framework for dynamically updating post-earthquake functional recovery forecasts is presented to reduce the epistemic uncertainty in the predictive model. A Bayesian Network (BN) model is used to ...provide estimates of the total recovery time, and a process-based discrete event simulation (PBDES) model generates forecasts of the complete recovery trajectory. Both models rely on component damage and duration-based input parameters that are dynamically updated using Bayes' theorem, as information becomes available throughout the recovery process. The effectiveness of the proposed framework is demonstrated through an application to the pipe network of the City of Napa water distribution system. More specifically, pipe damage and repair data from the 2014 earthquake are used as a point of comparison for the dynamic forecasts. It is shown that, over time, the mean value of the total recovery duration generated by the BN-based model converges to the observed value and the dispersion is reduced. Also, despite a crude initial estimate, the median trajectory generated by the PBDES model provides a reasonable approximation of the observed recovery within 30 days following the earthquake. The proposed framework can be used by emergency managers to investigate the efficacy of post-event mitigation measures (e.g. crew allocation, resource prioritization) utilizing the most current data and knowledge.
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NUK, OILJ, SAZU, UKNU, UL, UM, UPUK
AbstractThe goal of this paper is to facilitate a community of practice for disaster recovery modeling. This community should include hazard and disaster researchers without modeling experience and ...modelers with no experience in hazard and disaster research, not just the growing number of researchers that have experience with both. Disaster recovery modelers should develop mutual resources such as data sets, programming libraries, documentation, and terminology. For a community of practice to function, it needs to generate and appropriate a shared repertoire of ideas, approaches, and institutional memory. A potential shared repertoire of eight complimentary recovery modeling approaches to adopt, research, and advance is laid out. The largest need for lifeline recovery modeling—the most commonly researched recovery topic—is to research how to simulate lifeline infrastructure as sociotechnical systems in comprehensive, meaningful ways. For housing recovery modeling, a major gap is the inability to simulate rental dynamics, as well as the role of race and ethnicity. Lastly, a concerted and coordinated research effort is needed to create comprehensive platforms for simulating community recovery.
AbstractThe use of integral mechanical attachments (IMAs) in spatial free-form timber plate structures has been revitalized by the production of engineered boards and recent developments in digital ...fabrication and computer-aided design. Despite the widespread interest in utilizing such structural systems, there have been very few efforts to develop modeling strategies that can be used by practitioners. Detailed finite-element (FE) models are typically computationally expensive and require advanced expertise. Accordingly, this paper introduces a simplified yet robust macroscopic modeling technique for spatial free-form timber plate structures with IMAs. This approach employs only beam and spring elements to simulate the structural behavior. The macromodel was introduced and the associated mechanical properties were computed. FE models constructed using shell elements and the results from recent experiments performed on a full-scale prototype were used to verify the proposed macromodel. The results showed that the response of the macromodel was closely in line with that of the experiments and FE models. Despite its simplicity, the macromodel is robust and can simulate the behavior of integrally attached timber plates. It was also demonstrated that the computational time for the macromodel is significantly less than the FE simulation.
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