Effects of ground motion orientation on prediction of seismic demands of a single-story RC structure

This study investigates the influence of strong ground motion orientation on seismic response of a single-story reinforced concrete (RC) structures. For this purpose, three dimensional, single-story, single-bay asymmetric RC structure tested on shake table and its symmetric version are used. The numerical models of the structures in which reinforcement slip deformations taken into account are established according to the modelling technique validated in the "Blind Prediction Contest" conducted at the 15th World Conference on Earthquake Engineering. 30 pairs of near-field ground motion records are selected for bi-directional nonlinear time-history analyses. Horizontal components of ground motions are rotated from 0o to 360o with 10o increments. Selected and rotated ground motion records are scaled to get compatible with the target spectrum. Nonlinear time-history analyses are performed by applying simultaneously the horizontal components of those ground motions to the numerical models. The results for both asymmetric and symmetric structural models revealed that change in the ground motion incidence angle may result almost 4 times larger story drift ratio demands compared to the result obtained by using as-recorded ground motion records. However, when the averages of the maximum story drift ratio demand obtained from all analyses are considered, the change in the demands depending on the ground motion incidence angle remains around 15%.