Influence of ground motion duration on the dynamic deformation capacity of reinforced concrete frame structures

Data‐driven models for seismic damage and loss assessment of buildings have become more common in recent years due to the availability of large repositories of recorded and synthetic ground motions coupled with structural response simulation data. This paper explores the benefits of using bivariate and multivariate fragility functions to estimate earthquake‐induced damage and economic loss in high‐rise buildings. The dataset used in this study encompasses 15,000 simulations of modern high‐rise reinforced concrete shear wall buildings ranging from eight to 24 stories which are subjected to ground motion records at five different intensity levels. The proposed functions are conditioned on average spectral accelerations and ground motion significant duration. The results indicate that bivariate fragility functions improve damage state prediction success (Brier score) by 16%, and multivariate fragility functions by 24% relative to conventional univariate functions (standard of practice). To develop multivariate functions, nominal and ordinal probit regression models are fit to the dataset. While both models yield satisfactory predictive performance, ordinal functions can lead to a 15% reduction in misclassified collapse instances, that is, the minority class. Univariate functions tend to overestimate seismic losses at lower intensity levels while underestimating them at higher intensities. These loss estimates are significantly improved when bivariate or multivariate building fragility functions are used. Given the increase in the use of physics‐based ground motion simulations and/or multi‐variate ground motion models, from which multiple intensity measures can be extracted, a shift toward a more complex representation of fragility functions, for example, multivariate curves, is necessary and inevitable. The proposed functions are used to evaluate the performance of a portfolio of modern high‐rise reinforced concrete shear wall buildings at four sites across the Seattle, Washington metropolitan area under a potential magnitude‐9 Cascadia subduction zone earthquake scenario. The results indicate that the proposed functions can be beneficial in enhancing damage state predictions and loss estimates at a regional scale.

Section: Fragility Modelsmentioning

confidence: 99%

Toward multivariate fragility functions for seismic damage and loss estimation of high‐rise buildings

Kourehpaz,

Molina Hutt,

Lallemant

2023

“…Using the same set of motions, Hwang et al 29 quantified the effect of ground motion duration on economic losses in steel moment frame buildings and found that the most significant increase in loss results from duration's role in increasing collapse risk for mid-and high-rise buildings. Bhanu et al 30 quantified the difference in F I G U R E 1 Framework for assessing the level of damage at which a building's seismic performance is impaired dynamic deformation capacity-the level of story drift at which a building becomes unstable-of structures under longand short-duration motions, and found that longer duration motions are associated with a lower dynamic deformation capacity. They attribute this difference to the increased impact of cyclic deterioration and P-Δ effects when ground motions have a significant duration larger than 25 s.…”

Section: Related Previous Workmentioning

confidence: 99%

“…quantified the effect of ground motion duration on economic losses in steel moment frame buildings and found that the most significant increase in loss results from duration's role in increasing collapse risk for mid‐ and high‐rise buildings. Bhanu et al 30 . quantified the difference in dynamic deformation capacity—the level of story drift at which a building becomes unstable—of structures under long‐ and short‐duration motions, and found that longer duration motions are associated with a lower dynamic deformation capacity.…”

Section: Related Previous Workmentioning

confidence: 99%

A framework for assessing impaired seismic performance as a trigger for repair

Murray

Liel

Elwood

2021

Uncertainty about when post-earthquake repairs are needed delays decision making, and can lead either to unnecessary demolition or repair, or to inadequate repair actions. This study proposes a framework for assessing the effect of earthquake damage on the future seismic performance of a building. In this framework, we first assess drift demands during a maximum considered earthquake (MCE R ) level ground motion in an undamaged building, and then compare the drift demands in the same building during the same motion when it has been damaged by a prior shaking. We assess each building for a range of prior shaking events and 15 MCE R -level motions. From these analyses, we determine the relationship between damage in the first motion-quantified as peak story drift demand-and the MCE R -level motion drift demands-quantified as the ratio of peak drift demands in the damaged building to those in the undamaged building. This trend is used to indicate the level of damage at which performance is impaired, and repair is needed due to structural safety concerns. We apply this framework to a set of single-degree-of-freedom structures and reinforced concrete moment frame buildings representative of construction in the United States. The results show that code-conforming structures do not see significant drift amplifications in the damaged building when story drifts in the damaging motion do not exceed 2%, indicating they would not require major repairs for structural safety. Structures with less deformation capacity saw larger amplifications, and were affected when story drift demands in the damaging motion were lower. We also found that stiffer structures tend to see larger amplifications of drift demands.

“…2 Recent studies by the authors have made the case to potentially incorporate the "duration" factor in design by adjusting the dependable deformation capacities of structures as an alternative approach that can be more widely applied across different design codes. 9,10 This study makes use of the findings of these studies to derive such a method.…”

Section: Introductionmentioning

confidence: 99%

“…Recent studies by the authors on steel and RC moment frames found that as ground motion duration increases, not only do structures tend to collapse at lower intensities but also at smaller deformations. 9,10 The deformations associated with collapse, termed as dynamic deformation capacity (DDC), were found to be around 25% lower under a long duration set as compared to a spectrally equivalent short duration set for both kinds of frames.…”

Section: Introductionmentioning

confidence: 99%

Drift‐based risk‐oriented method for the explicit consideration of ground motion duration in seismic design

Bhanu,

Chandramohan,

Sullivan

2023

Self Cite

This study proposes a method to explicitly account for ground motion duration in seismic design by modifying structural deformation capacity. An equation is presented to adjust the design drift limit prescribed in the New Zealand standard NZS 1170.5, based on the anticipated reduction in structural deformation capacity for ground motion durations longer than a critical value. The proposed relationship is used to derive designs corresponding to three duration targets each for two case‐study steel moment frame buildings ‐ a 4‐storey and a 12‐storey, located on a site in Nelson, New Zealand. Hazard‐consistent collapse risk assessment of the design versions is conducted using a structural reliability framework employing incremental dynamic analysis. Results indicate that buildings designed for lower drift limits have a lower mean annual frequency of collapse. The application of the proposed method is found to reduce the variation in the collapse risk of steel frame buildings designed for different duration targets, compared to the existing approach. The method proposed in this study is simple and easy for practical applications and can be modified for other design codes and a range of structural typologies.