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

Abstract

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.

Incorporating potential environmental impacts in building seismic design decisions

“…Several studies have considered collapse scenario assessments, considering drift threshold for example 5% (Yeow et al 2018b), or 12% (Welsh-Huggins et al 2020). Recent work from Murray et al (2022) suggests that story drift higher than 2% would result in a building that might require major repair for structural safety. In lieu of robust guidance on non-repairable threshold limits, a reasonable value should be used based on characteristics of the structural system and relevant literature.…”

Seismic fragility assessment of a RC frame considering concentrated and distributed plasticity modelling

“…However, it has an inherent limitation on its formulation that makes the simulation of the strain softening associated with rebar buckling difficult [11]. Lumped plasticity models are frequently used in structural analysis [14]- [16], since it is easier to implement [17]. When calibrated properly, it can capture degradation of strength and stiffness that is essential to collapse modeling.…”