Cyclic Performance of RC Columns with Inadequate Lap Splices Strengthened with CFRP Jackets

The cyclic performance of non-seismically designed reinforced concrete (RC) columns, strengthened with carbon fiber reinforced polymer (CFRP) jackets, was analytically and experimentally investigated herein. Three cantilever column specimens were constructed, incorporating design parameters of the period 1950s-1970s, namely with concrete of a low compressive strength, plain steel bars, widely-spaced ties and inadequate lap splices of reinforcement. The specimens were strengthened using CFRP jackets and were subsequently subjected to cyclic inelastic lateral displacements. The main parameters examined were the length of the lap splices, the acceptable relative bar slipping value and the width of the jackets. The hysteresis behaviors of the enhanced columns were compared, while also being evaluated with respect to those of two original columns and to the seismic performance of a control specimen with continuous reinforcement, tested in a previous work. An analytical formulation was proposed for accurately predicting the seismic responses of the column specimens, comparing the actual shear stress value with the ultimate shear capacity of the concrete in the lap splice region. The test results verified the predictions of the analytical model, regarding the seismic performance of the strengthened columns. Moreover, the influences of the examined parameters in securing the ductile hysteresis performance were evaluated.