Theoretical Analysis And Numerical Simulation On Ultimate Bearing Capacity Of Square RC Short Column Strengthened With CFRP And Steel Tube

At present,due to design errors,improper construction,and functional changes of some reinforced concrete(RC)short columns in buildings,their bearing capacity is insufficient and cannot meet normal use functions.In consideration of economic viability and environmental protection,it is more reasonable and feasible to reinforce these buildings than to demolish and rebuild them.Therefore,it is necessary to study the reinforcement methods of RC short column.Existing studies have shown that CFRP and steel tube composite reinforced square RC short columns are effective and can significantly improve the bearing capacity,ductility,stiffness and other mechanical properties of the specimen.In order to further study the ultimate bearing capacity of CFRP and steel tube reinforced square RC short columns under axial compression and eccentric compression,based on the unified strength theory,this paper obtains the ultimate bearing capacity calculation formulas of the reinforced columns under axial load and eccentric load,carries out numerical simulations of the reinforced columns,and analyzes the stress and deformation of each component in the ultimate load.Based on these,this paper studies the influence of key parameters on the ultimate bearing capacity of the reinforced columns.The following are the main work and conclusions of this study:(1)Based on the unified strength theory,considering the influence of the section shape on the ultimate bearing capacity,using the limit equilibrium method,the ultimate bearing capacity theoretical formulas of the CFRP and steel tube reinforced square RC short columns under axial load and eccentric load are established.The ultimate bearing capacity formula under axial compression is degraded and analyzed.The verification results show that the formulas in this paper have high accuracy.(2)The initial stress method is used to apply the initial stress of the RC column to the reinforced column model.This paper establishes finite element models of the specimens under axial compression and eccentric compression.In addition,this paper verifies their correctness and analyzes reasons of errors.This paper further analyzes the stress and deformation of each part of the specimen,and the results show that the various materials of the specimen are fully used.Those show that the reinforced columns have good mechanical properties.(3)Using the previous theoretical formulas and finite element models to analyze models with different parameters,this paper studies how some parameters influence the ultimate bearing capacity of the reinforced column,and gets following conclusions: Increasing the thickness of CFRP and the thickness of steel tube,the ultimate bearing capacity of the reinforcement column under axial compression has a straight upward trend.The yield strength of steel tube and the strength of post-cast concrete have little effect on the ultimate bearing capacity of the reinforcement column under axial compression.The initial axial compression ratio of the RC column and the interface between the new concrete and the old concrete have no obvious influence on the ultimate bearing capacity of the reinforcement column under axial compression.Increasing the load eccentricity will significantly reduce the ultimate bearing capacity of the specimen under eccentric load.Increasing the thickness of CFRP and the strength of post-pouring concrete will significantly reduce the ductility of the specimen.