Seismic sequence effects on three-dimensional reinforced concrete buildings

Repeated earthquakes strongly affect the inelastic response of structures and cause in many cases more adverse effects in comparison with the corresponding single ground motions, such as the accumulation of structural and non-structural damage as well as the increment of deformation demands. Numerous research studies have been recently published in the pertinent literature to investigate this phenomenon but most of them are limited either to single-degree-of-freedom (SDOF) systems or to two-dimensional multi-degree-of freedom (2-D MDOF) systems such as multi-storey planar framed structures. With special regard to reinforced concrete (RC) buildings, this study investigates for the first time the inelastic response of three-dimensional (3-D) structures subjected to repeated earthquakes. More specifically, two three-storey and two five-storey RC buildings, which are regular and irregular along their height, are examined under five real strong multiple earthquakes where their two horizontal components as well as the vertical one are taken into account. The investigation focuses on the examination of the maximum displacements, maximum residual displacements, maximum interstorey drift ratio, maximum residual interstorey drift ratio, damage indices and ductility demands. Finally, the building structures under consideration are analyzed for different siting configurations to investigate the effect of earthquake direction incident. It is concluded that the multiplicity of earthquakes should be taken into account for the reliable seismic design of reinforced concrete structures.