Research On Seismic Behavior And Design Calculation Theory Of Seismic-damaged Steel Reinforced Concrete Frame Structures With Strengthening

Steel reinforced concrete(SRC)structure possesses excellent seismic behavior and good endurance.Seismic damaged buildings are unsuitable for integral overthrow reconstruction or blind reinforcement.Structures or components of unreasonable reinforcement suffered from earthquake again,which causes catastrophic damage,tend to immediate or progressive collapse resulting in a large number of casualties and economic losses.Therefore,it is necessary to propose a reliable retrofitting method for seismic-damaged SRC structures and to study how to evaluate the seismic performance and shear strength of structures after retrofitting.The main contents are described as follows:1.Experimental research on seismic behavior of seismic-damaged SRC frame columns and frame joints with strengthening.Ten 1/2-scaled frame column models and nine 1/2-scaled frame joint models are designed and manufactured according to the current codes.Seismic retrofitting on damaged models is conducted using carbon fiber reinforced polymer(CFRP)and enveloped steel jacket.Seismic performances of models before and after retrofitting are studied under lateral cyclic loads test method.Destruction mode,hysteretic curves,skeleton curves,energy-dissipating capacity,strength degradation,stiffness degradation and displacement ductility of models before and after retrofitting under lateral cyclic loads are acquired.Seismic performance and retrofitting effects of models before and after retrofitting are compared and analyzed.2.Experimental research on seismic behavior of seismic-damaged SRC frame structures strengthened with enveloped steel jackets.According to current codes,an one third scaled 2 bays,3-stories model of SRC frame is designed and manufactured.The under lateral cyclic loads test method is used to simulate the seismic damage.Enveloped steel jacket is applied on retrofitting the seismic damaged models,and the experimental research on its seismic behavior is performed under lateral cyclic loads.Hysteretic curves,skeleton curves,ductility coefficients,energy dissipation coefficient,stiffness degradation and bearing capacity degradation of the specimens before and after retrofitting under lateral cyclic loads are acquired.Seismic performance of models before and after retrofitting are analyzed.3.Nonlinear finite element analysis on seismic behavior of seismic-damaged SRCstructures with strengthening.Based on the reduced material performance method,the relationship between the damage index and the constituent materials is constructed.A three-dimensional finite element analysis model is established by using ABAQUS finite element software,and the calculated results are much coincided with the tested results.4.Shear capacity analysis of seismic-damaged SRC frame columns and frame joints with strengthening.Based on the “truss-arch” model theory,the theoretical formula for calculating the shear capacity of seismic-damaged SRC frame columns after retrofitted is derived.The resistant mechanism and failure pattern of SRC frame joint are analyzed based on experimental and finite element analysis.Horizontal resisting elements are determined,and the theoretical formulas for calculating the shear capacity of seismic-damaged SRC frame joints after retrofitted are proposed.The calculated results are much coincided with the tested results,which indicate that the formula is feasible.