Simplicity versus accuracy trade-off in estimating seismic fragility of existing reinforced concrete buildings

This paper investigates the trade-off between simplicity (modelling effort and computational time) result accuracy in seismic fragility analysis of reinforced concrete (RC) frames. For many applications, simplified methods focusing on “archetype” structural models are often state-of-practice. These approaches may provide a rapid-yet-accurate estimation fragility, requiring relatively small amount input data resources. However, such fail to capture specific deficiencies and/or failure mechanisms that might significantly affect final assessment outcomes (e.g. shear beam-column joints, in-plane out-of-plane infill walls, among others). To overcome these shortcomings, alternative response considered this all characterised by mechanics-based approach explicit consideration record-to-record variability modelling input/demands. Specifically, compares three different approaches, each refinement: 1) low refinement - non-linear static (either analytical SLaMA or pushover analysis), coupled with capacity spectrum method; 2) medium time-history equivalent single degree freedom (SDoF) systems calibrated based either SLaMA-based pushover-based force-displacement curves; 3) high multi-degree (MDoF) numerical models. In cases, curves derived through cloud-based employing unscaled real (i.e. recorded) ground motions. 14 four- eight-storey RC frames showing plastic distribution infills analysed using method. The results show SDoF is not substantially superior respect estimated median (for damage states) generally falls within ±20% (generally as an under-estimation) corresponding estimates from MDoF analysis, slightly-higher errors for uniformly-infilled latter error range increases up ±32%. dispersion over-estimated 30%. Although bias levels non-negligible, their rigorous characterisation can potentially guide analyst select/use derivation approach, depending needs context, calibrate appropriate correction factors more methods.