Influence of ground motion duration on damage index-based fragility assessment of a plan-asymmetric non-ductile reinforced concrete building

The role of ground motion duration on the seismic performance of building structures remains unclear. This paper presents results on the effects of ground motion duration on the seismic behaviour of a 3-D plan-asymmetric reinforced concrete building. A three-story reinforced concrete building tested in Europe is used as a case study. A nonlinear model of the building with fibre-section distributed inelasticity displacement-based beam-column elements is subjected to two ground motion sets: (1) long-duration bi-directional earthquake ground motions, and (2) short-duration bi-directional earthquake ground motions. A new ground motion selection procedure is proposed to isolate the effect of duration on the structural response and on damage assessment. For comparative studies, long- and short-duration ground motions are selected so that they have similar response spectra. The damage assessment is performed analysing global and local responses. Global responses of the structure are evaluated in terms of peak roof drift ratios, peak interstory drift ratios (IDRs), IDR envelopes, normalized roof displacements relative to motion of the centre of gravity of the roof, and dissipated energy. Local responses assessed include moment-curvature or moment-rotation response in beams and columns as well as the hysteretic energy dissipated at selected sections of the structure. Two damage indices available in the literature are used to characterize the level of damage that the structure experiences, through damage index-based fragility curves that are developed as part of the work. For the short-duration motions, fragility curves developed independently from interstory responses and from the damage indices are similar, thus providing confidence into the use of the damages indices for fragility curve development. In addition, results indicate that for the vintage plan-asymmetric building analysed, the ground motion duration plays a role in the damage predicted using the two damage indices.