Seismic Behavior And Structural Vulnerability Analysis Of FRP Confined Steel Reinforced UHPC Composite Columns

With the development of China’s engineering construction in the direction of towering,heavy load and long span,it is difficult for traditional reinforced concrete structures to meet the service needs of structures.The combined structure has become an important structural form from the idea of double optimization of material and crosssectional form.In this paper,the combined column form of Fiber Reinforced Composite(FRP)constrained section steel-ultra high performance concrete(UHPC)is proposed,and the cross-section steel with flange is placed in the center of the FRP pipe,and UHPC is poured in the void part to form an FRP-steel-UHPC composite column.The advantage of this combined column is that the lateral expansion of internal UHPC can be effectively reduced through the strong constraint of FRP,thereby improving the compressive performance and ductility of UHPC,and can also prevent the premature buckling of the internal section steel from instability failure.In addition,FRP pipe can be used as a formwork to improve construction efficiency and protect the environment.In this project,the quasi-static test of five FRP-constrained steel UHPC composite columns was carried out,and the ductility,stiffness and energy dissipation of the composite columns were analyzed.The results show that the composite column has the advantages of high bearing capacity,good ductility,high stiffness and high energy consumption.Based on the flat-section assumption,the calculation model of the combined column bending bearing capacity is derived,and the bending bearing capacity curve is drawn,and the comparative test results show that the proposed model has good accuracy.Furthermore,according to the reasonable stiffness ratio of beam and column,the composite column design is applied to a frame structure,and based on IDA analysis,the seismic risk curve and seismic hazard probability model of the frame structure using the combined column are obtained,and the safety reserve coefficient of the structure collapse resistance is calculated according to the seismic vulnerability curve and seismic risk probability model.