Seismic Performance Analysis of Concrete Composite Torsional Columns Strengthened with CFRP Based on Cohesion Model

The mechanical properties of CFRP-concrete interface are important factors affecting the seismic performance of CFRP reinforced structures. A bilinear cohesive force unit based on nonlinear softening mechanical behavior was established to simulate the bonding interface of CFRP reinforced structures. Considering the material nonlinearity of concrete and rebars, the seismic performance of CFRP reinforced concrete composite torsional columns was analyzed by finite element method. In order to verify the rationality of the method and improve the arrangement of CFRP, the stress variation, the failure mechanism of the interface and the bearing capacity of the structure were analyzed. The results were compared with the experimental results and the finite element analysis results without considering the interface bonding slip. The results of finite element analysis showed that the tensile stress, bonding interface stress and damage variables of CFRP were large in the middle and corners of the section, but small at the junction of CFRP. The stripping failure expanded from the edge of CFRP with large stress to the middle during the loading process. The structural failure process obtained by finite element analysis was basically consistent with the experimental results, which revealed the influence of bonding interface degradation on the seismic performance of CFRP reinforced concrete columns. The relative error between the maximum load obtained at each stage and the experimental results was less than 10%. Without considering the degradation of bond interface properties and the stripping of CFRP, the contribution of CFRP to the bearing capacity in the strengthening stage was overestimated. The cohesive force model of bond interface could provide a reference for seismic performance analysis of CFRP reinforced concrete composite torsional columns.