The Progressive Collapse Behavior Of Steel-FRP Composite Bar Reinforced Concrete Frames

Explosion,fire or other accident loads may cause disproportionate or overall structural collapse,resulting in heavy casualties and property loss.Nowadays,reinforced concrete structure is one of the most widely used forms,how to improve the anti-progressive collapse ability of RC frames is an urgent problem to be solved.Combining the advantages of FRP and steel bars,SteelFRP composite bar(SFCB)exhibits stable post-yield stiffness,corrosion resistance,high tensile strength and mature industrialized preparation technology,all of which provide new ideas and research directions for strengthening the resistance of RC structures.Based on the actual structure,according to the 1:2 scale,nine beam-column substructures consisting of short columns and two-span continuous beams are designed to simulate the failure of the interior column of the RC structures.Ordinary steel bars are replaced by SFCB for the first time to study the progressive collapse resistance of SFCB reinforced concrete structures,and the model is studied by numerical simulation.The main works are as follows:In order to study the effect of SFCB on the progressive collapse performance of concrete structures,specimens were reinforced by SFCB with different post-yield stiffness ratios and FRP.SFCB was divided into FRP bars and steel bars separately for mixed configuration.Through the vertical quasi-static test method based on displacement control,the failure mode,peak capacity,load-displacement curve and crack development of different specimens were obtained.The effects of the SFCB on the continuous collapse performance of the concrete structure were compared.Nonlinear analysis on the progressive collapse behavior of each specimen was carried out by finite element software MSC.Marc.The load-displacement curve,the failure position and the strain were studied and compared with the test results.The results show that the model is agreeable with the ordinary reinforced concrete structures.The specimens with SFCB or mixed configuration have a high degree of coincidence in the flexural action and the arch compressive action,but there is a certain error in the catenary action.Aiming at concrete structures with ordinary steel bars,SFCB and mixed configuration,the formulas for calculating the peak bearing capacity of flexural action,arch compressive action and catenary action are proposed and compared with the experimental and simulation results.In the first two stages,the gap between the three results is small.In the catenary action stage,the calculated value is close to the simulated value,but larger than that of experiment.