A Combined-Index Study on the Influence of Earthquake Incidence Angle on the Seismic Performance of Reinforced Concrete Plan-Asymmetric Buildings

A study is performed to estimate the critical seismic incidence angle for a nine-story reinforced concrete dual system building, categorized as plan-asymmetric, by considering a combination of two demand parameters, the Maximum Inter-story Drift (MLID) along the height, and the Seismic Vulnerability Index (SVI). The influence of excitation directionality on the response of the building was investigated by nonlinear dynamic analyses, by applying seven scaled bidirectional ground motion records, oriented in eight incidence angles ranging from 0° to 315°, with a 45° increment. The scaling was made for a peak ground acceleration PGA = 0.30g, according to the elastic response spectrum specified for Bucharest by the Romanian seismic code P100-1/2013. From the results, it was found that the most unfavourable response due to a specific seismic excitation may occur at any angle of incidence, which is not necessarily 0° or 90°, and that the response depends not only on the structural configuration, but also on the excitation characteristics. In addition, the influence of the flexible edge (FE) on the structural demand in terms of SVI was studied. The maximum values for SVI were obtained for the most critical angle of incidence, which is the one that has the higher MLID values in the FE for all accelerograms.