THE İNFLUENCE OF THE AXİAL LOAD VARİATİON ON THE SEİSMİC CAPACİTY OF EXİSTİNG RC BUİLDİNGS

ABSTRACT The paper deals with the role of axial load on the seismic performance of existing RC buildings. The axial load variability is often neglected in seismic analysis, despite it can largely affect the capacity of RC columns. The limit chord rotation of columns, in fact, is a function of the amount of axial load. The sensitiveness of the rotational capacity of a column to axial load depends even by its concrete strength. If concrete presents poor mechanical properties, in fact, the sensitiveness of the columns’ capacity to the axial load is larger. In this work the axial load variation has been considered both in the seismic demand and capacity on a case-study, i.e. a 3D RC framed structure designed for vertical loads only. As regards the seismic demand, the relationship between axial load variation and type of performed analysis has been checked, by performing both a nonlinear static and a time-history analyses, in order to evaluate the effect of the dynamic response of the case-study on the axial load variation. As regards the seismic capacity, it has been found by considering the effective amount of axial load in each column and different assumptions about the concrete strength characterization.