Axial Compression Behavior Of CFRP Confined Rectangular Concrete-filled Stainless Steel Tubular Stub Columns

Carbon fiber reinforced polymer(CFRP)is widely used in engineering construction and damaged reinforcement due to its high specific strength.At present,there are systematic researches on CFRP confined concrete short columns and common carbon steel tube concrete short columns at home and abroad,but the research on CFRP confined stainless steel tube concrete(CFSST)is still in its infancy.Therefore,this paper systematically studies the compression bearing capacity of CFRP-CFSST composite members.In order to understand the mechanical properties and failure mechanism of CFRP confined concrete-filled rectangular stainless steel tubular stub columns under axial compression,28 specimens of 7 groups were tested under axial compression,and the effects of length width ratio,CFRP layers and steel tube thickness on the axial compression properties of specimens were studied.The results show that the bonding of CFRP has obvious effect on improving the compression bearing capacity of members;increasing the thickness of steel tube can effectively improve the bearing capacity of specimens,and the larger the length width ratio is,the more prone the specimens are to be subjected to compression bending failure,resulting in the decline of bearing capacity.Based on the analysis of the stress situation of CFRP-CFSST composite members under compression,the compression bearing capacity of the members is divided into three parts: the compression bearing capacity of stainless steel tube,the compression bearing capacity of core concrete and the benefit of CFRP reinforcement.Combined with the unified theory of twin shear strength and von Mises yield criterion,the calculation formula of bearing capacity with high effectiveness and reliability is put forward.In order to further study the influence of various parameters on the bearing capacity of CFRP-CFSST composite members,the finite element model of CFRP-CFSST composite members was established by using ABAQUS software.The factors influencing the finite element numerical simulation results,such as element type,material properties,mesh generation,boundary conditions and contact treatment,were discussed.The failure mode,peak load and load displacement diagram obtained by numerical simulation are compared with the experimental results respectively.The results show that the finite element model established in this paper has higher accuracy.At the same time,the load displacement curves of composite members under different parameters are compared and analyzed,the failure mode and ultimate bearing capacity of components under different parameters are obtained,and the influence of concrete strength on the bearing capacity of composite members is further analyzed.It is found that with the increase of concrete strength,the bearing capacity of the member increases,but the increase range decreases with the increase of concrete strength.