Axial compressive strength of preloaded CHS stubs strengthened by CFRP

Abstract

Failure process of circular hollow section (CHS) stubs strengthened by carbon fiber reinforced polymers (CFRP) at both unloading and preloading conditions was experimentally investigated. A total of 11 CHS stub specimens were tested under axial compressive loads. The specimens are divided into three categories: un-strengthened CHS stubs, CFRP-strengthened CHS stubs at no preloading condition, and CFRP-strengthened CHS stubs at preloading condition. The compressive strengths of the specimens were investigated by considering the effects of several parameters including preloading percentage, the number of CFRP laminates, the tube thickness and the configuration of CFRP laminate. For the preloaded CHS stubs, their yield strengths after CFRP strengthening reduce slightly with an increase of the preloading. However, the ultimate strengths of the CFRP-strengthened CHS stubs at different preloading percentages are almost same, i.e., the CFRP strengthening efficiency is not influenced by the preloading conditions. Finite element (FE) model was also established, and the accuracy of the FE model is verified through comparing the FE simulations with the experimental results. Using the presented FE model, parametric study is carried out to study the efficiency of CFRP strengthening technique to improve the ultimate strength of CHS stubs at preloading condition. The effects of wall thickness and diameter-to-thickness ratio of the steel tube and the CFRP wrapping method on the strengthening efficiency of CFRP to CHS stubs are also investigated.