Seismic Fragility Analysis Of Knee Braced RC Frame Structure Under Strong Earthquake

The ordinary reinforced concrete frame structure has low lateral stiffness,large lateral deformation and weak seismic resistance.Proper bracing in ordinary reinforced concrete frame structure can significantly improve the lateral stiffness of the structure,reduce the deformation of the structure,and increase the ability of the structure to resist earthquake damage.In this paper,the seismic performance of concrete frame structures supported by knee-braces is studied,and the application of knee-braces to seismic performance of concrete frame structures is analyzed.The main research contents of this paper include several aspects:(1)The effects of column section,eccentricity,high span ratio and axial force on the bearing capacity,stiffness,ductility and energy dissipation capacity of the structure are discussed through the finite element analysis of the single-layer duct-braced concrete frame structure.The results show that there are some differences in the seismic performance of the braced concrete frame structure under different column sections,different eccentricities,different height span ratios and different axial forces.(2)The effect of the knee-brace brace on the seismic performance of the multi-storey concrete frame structure was studied.The OpenSees finite element analysis software was used to compare and analyze the mechanical performance of the 5-storey ordinary concrete frame and the knee-brace brace concrete frame under the 8-degree fortification earthquake in common and rare earthquakes.The energy dissipation capacity and bearing capacity of the whole structure are improved,and the residual deformation is reduced by the application of the knee brace.(3)IDA method was used to compare and analyze the strong earthquake vulnerability of ordinary concrete frame and pin-braced concrete frame,and the analysis results showed that: Under the action of different types or intensities of ground motion,there are many differences in seismic performance and damping effect between the pin-supported frame and the pure frame,but on the whole,the seismic response of the pin-supported frame is much smaller than that of the pure frame,and the damping effect is enhanced with the increase of vibration intensity.The anti-collapse ability of the pin-supported frame is obviously stronger than that of the pure frame.