Extensive experimental investigations into the behavior of reinforcement concrete and steel frames with infill have been conducted worldwide. However, there are very few systematically created and ...publicly available databases on infilled frame experiments. This article assembles a database of 264 experiments on single-story infilled frames, which includes specimens with different types of frames and panels. It has been utilized by the authors (in separate studies) to develop (1) empirical equations for modeling the infill panels as equivalent struts and (2) machine learning models for failure mode classification. The intent is for the database to be augmented and further used in various other applications in studying the seismic behavior of masonry-infilled frames.
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NUK, OILJ, SAZU, UKNU, UL, UM, UPUK
AbstractDuring an earthquake, buildings are simultaneously excited by multiple (horizontal and vertical) ground motion components. In the design process, the combinatorial effects of multicomponent ...horizontal loading are commonly determined using simplified methods such as the percentage (e.g., 100%–30%, 100%–40%) and square root sum of squares (SRSS) rules. In this paper, the state of the art in assessing the effectiveness of combination rules for orthogonal seismic effects is first reviewed. Prior studies are categorized based on the adopted analysis method (e.g., response spectrum versus response history), type of structural system, presence of structural irregularities, and considered demand parameters. A recent attempt to evaluate the combination studies using strong motion data is also discussed. Subsequently, the adoption of combination rules in popular codes and standards is presented and discussed including the conditions that trigger their implementation. Based on the review of prior research on the topic, it is concluded that the structural engineering community has not reached a consensus on the relative effectiveness of the various orthogonal combination methods. The paper concludes with a comprehensive discussion that covers specific challenges, knowledge gaps, and suggestions for future research.
This paper presents a computationally efficient collapse fragility assessment approach that leverages the collaborative filtering (CF) technique. The proposed method randomly selects and runs a ...subset of the nonlinear response history analyses (NRHAs) required for the incremental dynamic analysis. The structural performance in the omitted cases is then estimated using CF, which requires significantly less time and effort than the nonlinear structural analysis. The NRHA‐based and CF‐generated building performances are then assembled to determine the empirical probability of collapse at each intensity, which is later fitted with a lognormal distribution to obtain the median collapse capacity and associated dispersion. The proposed approach is applied to three steel moment frames, demonstrating that it can reduce the required NRHAs by 50% while providing a reliable collapse fragility estimate for the selected ground motion sets (FEMA P695 44 far‐field records and a site‐specific record‐set). The results from sensitivity analyses reveal that the proposed method is reasonably robust unless the input parameters are assigned extreme values.
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BFBNIB, FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SAZU, SBCE, SBMB, UL, UM, UPUK
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
Aftershocks can exacerbate the financial losses and functionality disruption to buildings damaged by a preceding mainshock event. A framework is presented for determining the optimal set and timing ...of activities that are performed on an earthquake-damaged tall building in the aftershock environment. The optimization objective is to minimize the cumulative aftershock loss while considering the necessary safety precautions. To this end, the Markov Process and Dynamic Programming methodology are implemented. The specific post-mainshock actions that are considered include whether to evacuate the building, when to reoccupy the building if it was previously evacuated, whether to repair the building and if so, when to start and stop the repairs. The results for a 42-story reinforced concrete building show that the algorithm is able to balance the need for evacuation during the period of high aftershock seismic hazard with a timely resumption of occupancy and necessary repair activities to minimize functional disruption.
•A framework for optimal decision-making for earthquake-damaged tall buildings in the aftershock environment is presented.•The Markov Process for mainshock-aftershock risk-based assessment is integrated with Dynamic Programming (DP).•The optimization seeks to minimize the cumulative aftershock loss while ensuring repair-worker and occupant safety.•The DP balances the tradeoff between repair-worker and occupant safety and the disruption cost of the evacuated building.•When the decision is made to repair the damaged building, the optimal time to start and stop the repairs is assessed.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
Event‐based methods are commonly used to assess the risk to distributed infrastructure systems. Stochastic event‐based methods consider all hazard scenarios that could adversely impact the ...infrastructure and their associated rates of occurrence. However, in many cases, such a comprehensive consideration of the spectrum of possible events requires high computational effort. This study presents an active learning method for selecting a subset of hazard scenarios for infrastructure risk assessment. Active learning enables the efficient training of a Gaussian process predictive model by choosing the data from which it learns. The method is illustrated with a case study of the Napa water distribution system where a risk‐based assessment of the post‐earthquake functional loss and recovery is performed. A subset of earthquake scenarios is sequentially selected using a variance reduction stopping criterion. The full probability distribution and annual exceedance curves of the network performance metrics are shown to be reasonably estimated.
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BFBNIB, DOBA, FZAB, GIS, IJS, IZUM, KILJ, NLZOH, NUK, OILJ, PILJ, PNG, SAZU, SBCE, SBMB, UILJ, UKNU, UL, UM, UPUK
As an alternative to conventional seismic force resisting systems, controlled rocking steel braced frames (CRSBFs) can effectively eliminate permanent structural damage after earthquakes. Together ...with the rocking action in the braced frame, post-tensioning (PT) elements and fuse members are used to provide self-centering and energy dissipation, respectively. This study firstly aims to assess the influence of design parameters related to the fuse and PT materials on the seismic response of CRSBFs. These factors include the yield strength, initial stiffness, and strain hardening ratio of the fuse, the initial force and modulus of elasticity of the PT strands, and the gravity load on the rocking column. Additionally, different analysis cases are considered to include the effects of frame aspect ratio and earthquake intensity level. Nonlinear response history analyses are performed with factor combinations generated using a design of experiment methodology. The second goal of the study is focused on optimizing the seismic response of CRSBFs with respect to the influential factors identified in the sensitivity analyses. Using a response surface methodology and desirability approach, multiple-response optimization is applied to determine the design variable values needed to simultaneously minimize the maximum transient and residual roof drift ratio and peak floor acceleration. Among other results, it is found that the fuse strain hardening ratio and PT strand modulus of elasticity do not significantly influence the seismic response demands in CRSBFs. The results of the multi-response optimization demonstrate that the initial PT force is most useful for minimizing all three seismic response demand parameters.
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EMUNI, FIS, FZAB, GEOZS, GIS, IJS, IMTLJ, KILJ, KISLJ, MFDPS, NLZOH, NUK, OBVAL, OILJ, PNG, SAZU, SBCE, SBJE, SBMB, SBNM, UKNU, UL, UM, UPUK, VKSCE, ZAGLJ
This study aims to compare the collapse probability of reinforced concrete infilled frames designed in accordance with modern Indian seismic codes. Multiple versions of bare and infilled (both fully ...and partially) frames are considered. A total of 33 frames are divided into eight sets based on the parameter being varied, namely, the quality and thickness of infills, design code, aspect ratio, and number of stories. The collapse probability is evaluated through multiple stripe analysis with eight stripes corresponding to different return periods. A set of 40 ground motions, consistent with the site-specific uniform hazard spectra corresponding to each return period, is selected. Results suggest that the frames designed for pre-2016 Indian codes perform considerably worse than those designed for post-2016 Indian codes, which are on par with other national codes. The effect of collapse probability of addition of infills to bare frames is found to be negligible to significantly negative depending on factors such as adopted design code, relative strength of infill strut to columns, aspect ratio, and number of stories. Four-story frames perform worse than 8-story frames. Interestingly, the 8-story open first story frames, designed for modern codes, are not found to be significantly more vulnerable than their fully infilled counterparts.
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NUK, OILJ, SAZU, UKNU, UL, UM, UPUK
•A quantitative relationship between 100/p% rule and collapse risk is built.•SCBF building designs based on 100/30%, 100/65%, and 100/100% rule are compared.•Collapse could occur due to inadequate ...100/p%-rule-based column force demand.•Taller buildings benefit more from conservative 100/p% rule in column design.•Collapse risk does not change linearly with the p value in 100/p% rule.
In the seismic design of structures, the combinatorial effects of multiple horizontal ground motion components are often determined using the 100/p% percentage rule (i.e. designs based on 100% in one direction and p% in the other). In this study, a reliability-based methodology is developed to explicitly link building collapse caused by percentage-rule-based-underestimation of the design force demands to the adopted p% value. The methodology is applied to three special concentrically braced frame (SCBF) buildings (4, 8, and 12 stories) with corner columns shared by orthogonal frames. Each building case is designed using the 100/30%, 100/65%, and 100/100% percentage rule. Response history analyses using bidirectional and unidirectional loading are performed on nonlinear structural models to obtain the “true” demands and percentage-rule-based demands, respectively. Models constructed with and without considering SCBF column failure are utilized within the overall reliability-based framework to isolate the effect of underestimated design force demands on collapse performance. A quantitative relationship between the adopted p% value and building structural collapse risk is established. The results show that there is a nonlinear relationship between an increase in p% and the benefits in terms of reduced collapse risk. Also, taller buildings are shown to benefit more from conservative (higher) p% values compared to shorter ones.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
•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
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