Push-over analysis of underdesigned r.c. frames: a case study in Catania

Most of the existing reinforced concrete buildings were designed according to early seismic provisions or, sometimes, without applying any seismic provision. Some problems of strength and ductility, like insufficient shear strength, pull-out of the rebars, local mechanism, etc., could characterize their structural behaviour. Therefore the presence of these problems requires a refined procedure of assessment of existing r.c. structures. For this aim an useful tool can be the pushover analysis of the structures, that is suggested by different advanced code and provisions. In this paper an innovative numerical model is presented. This model allows to take into account the most important mechanical phenomena that influence the non-linear behaviour of the reinforced concrete frames. The push-over analysis is made using a refined point by point model including an explicit formulation of the bond slip relationship and capable to take into account the effect of the distributed and concentrated non-linearity as the spread of plasticity along the member and the fixed end rotation. The results of the pushover analysis of an existing underdesigned building are also presented. This analysis includes also the estimation of the local demand of curvature ductility in beams and columns that is related with the interstorey drift.