Strengthening of circular RC column-foundation connections with GFRP/SMA bars and CFRP wraps

摘要

In this study, a new method is proposed for strengthening circular reinforced concrete (RC) column to foundation connections with Glass fiber reinforced polymer (GFRP) and shape memory alloy (SMA) bars and carbon fiber reinforced polymer (CFRP) wraps. Six specimens of circular RC column-foundation connections were cast and tested. One specimen was used as the control; i.e., without strengthening. Two specimens were strengthened with longitudinal GFRP bars of different sizes. The fourth specimen was strengthened with the combination of longitudinal GFRP bars and CFRP wraps. The two other specimens were strengthened with longitudinal SMA bars; one with and the other without CFRP wraps. The column top of these specimens was under a constant axial compressive load and cyclic lateral displacements, simultaneously. Through a set of laboratory tests, the parameters of lateral load capacity, energy dissipation capacity, residual displacement, initial stiffness, and ductility ratio of the specimens were studied. Test results showed that these parameters were improved significantly in the specimens strengthened with GFRP bars compared to the control specimen. The SMA strengthening bars were able to reduce the residual deformation of the connections. Also, the combination of the SMA bars and CFRP wraps increased the ductility ratio parameter. In the analytical part of the study, a subroutine was adopted for modeling the SMA materials. This subroutine was linked with ABAQUS software for the analysis. The analytical results showed a good correlation with the experimental results.