Abstract

The results of an experimental program on two-way reinforced concrete (RC) flat slabs under punching shear due to central loading are presented in this paper. All the six RC slabs were designed according to ACI 318-08 code provisions. Two slabs served as control without any modification while the other four were strengthened in different ways: one with M16 screws and nuts, and three with CFRP rods. For strengthening in each case, 8 and 24 strengtheners were used. A method is proposed for predicting maximum loading capacity of slabs strengthened with CFRP rods and with epoxy resin in drilled holes. The results of the experiments showed that the selected strengthening method was not only able to improve the maximum loading and deformation capacity of the slabs but also avoided brittle failures likely to occur under vertical point loadings.

Introduction

Despite their wide applications in buildings and bridges in the past, reinforced concrete (RC) flat slabs have recently become a source of concern for their vulnerability to damage or failure in many old structures due to changes both in their usage and loading and in the relevant updated design codes. As a remedy to this situation, much attention in recent years has been focused on strengthening RC flat slabs. Attempts by many investigators to increase the shear capacity of existing slabs include, but are not restricted to, adding steel bars, steel rods, and shear bolts; steel jacketing; increasing column size; and applying FRP sheets or stirrups.