Influence of FRP wrapping on reinforcement performances at lap splice regions in RC columns

Lap-splice regions are amongst the most critical regions of Reinforced Concrete (RC) members, especially in seismic design. The goal of wrapping with Fibre Reinforced Polymer (FRP) is provide confinement to concrete, however, a further important role is either to increase the bond between the reinforcement bars (in pre-cracked conditions) or to provide for bond (in fully cracked cover conditions). The proposed study aims to quantify the beneficial effect of this retrofit technique on the performance of the longitudinal reinforcement with a first attempt to account explicitly for the pointwise variability of confining stresses. For this purpose, both the reinforcement bar working stress and the anchorage length needed to prevent the bar slippage have been analytically assessed. The model has been validated against experimental tests and a good agreement with the model predictions has been found in both the cases of square and rectangular cross sections.