Finite element modelling of CFRP jacketed CFST members under flexural loading

In this era, using concrete filled steel tubular (CFST) members has become very popular in the construction industry; at the same time, ageing of structures and deterioration of members are often reported. Therefore, actions like implementing strengthening techniques with the new materials become essential to combat this problem. Due to their in-service and superior mechanical properties, carbon fibre reinforced polymer (CFRP) composites make an excellent candidate after upgrading. The aim of this study is to experimentally investigate the suitability of CFRP in strengthening of CFST members under flexure. Among eighteen beams, nine beams were strengthened by full wrapping (fibre bonded at the bottom throughout the entire length of beam) and the remaining nine beams were strengthened by partial wrapping (fibre bonded in-between loading points at the bottom). The effect of CFRP layers on the moment carrying capacity of CFST beams was investigated. Also a nonlinear finite element model was developed using the software ANSYS 12.0, to validate the analytical results such as load–deformation and the corresponding failure modes. The experimental results revealed that beams strengthened by partial wrapping failed by delamination of fibre, even before attaining the ultimate load of control beam but the beams strengthened by full wrapping exhibited more enhancements in moment carrying capacity and stiffness. From the numerical simulation and experiments, it is suggested that if any appropriate anchorages are provided in partial wrapping scheme to avoid delamination of fibre, then it will be turned into a fine and economical method for strengthening of CFST members.

► This study aimed to develop optimum wrapping schemes of FRP technology for CFST beams under flexure.
► CFRP strengthening significantly increases the moment carrying capacity of the CFST members.
► Data are used to develop design guidelines for the design of FRP strengthened steel structures.