Study On Seismic Performance And Fragility Of Concrete Columns With HRB635 High-strength Reinforcement

The use of high-strength steel bars in reinforced concrete members can effectively reduce the amount of steel bars and solve the problem of steel congestion,which has obvious economic advantages and reduces the difficulty of construction.At present,the research on the seismic performance of concrete columns with 600 MPa and above high-strength reinforcement in China and abroad is not sufficient.In order to provide theoretical and experimental basis for the popularization and application of high-strength steel bars,this paper studies the seismic performance of HRB635 high strength reinforced concrete columns.The main research work and results of this paper are as follows:(1)Ten concrete columns with HRB635 high-strength steel bars and two concrete columns with HRB400 steel bars as longitudinal reinforcement equal-strength substitution control groups were tested by quasi-static test.The loading process and failure mode of the specimens were studied,and the hysteresis curve,skeleton curve,bearing capacity,ductility and energy dissipation performance of the specimens were analyzed.(2)According to the test results,the influence of key parameters,such as axial compression ratio,concrete strength,stirrup strength,longitudinal reinforcement strength and longitudinal reinforcement equivalent strength substitution,on the stiffness,bearing capacity,deformation and energy dissipation capacity of high-strength reinforced concrete columns was evaluated.The strain variation of longitudinal reinforcement in specimens and whether the strength of HRB635 steel bars can be fully utilized when used as longitudinal reinforcement in column members are analyzed.(3)Based on the Open Sees software,the finite element simulation analysis of the stress process of the test specimen is carried out.By comparing with the experimental results,the rationality and feasibility of the analysis model are verified.The influence of concrete strength,design axial compression ratio,stirrup strength and unilateral reinforcement ratio on the seismic performance of high strength reinforced concrete columns is further analyzed and evaluated by using the checked finite element analysis model.(4)Five damage states of high-strength reinforced concrete column are proposed,and the damage phenomena are described.The quasi-static test specimens of high-strength reinforced concrete columns at home and abroad are collected.The displacement angle is selected as the deformation performance index,and the displacement angle of the specimens corresponding to each damage state is counted.The logarithmic normal distribution form is used to fit the experimental displacement angle datas under various damage states,and the vulnerability curve of high-strength reinforced concrete columns is established.By goodness-of-fit test,the two are in good agreement.The influence of design parameters such as design axial compression ratio,shear-span ratio,concrete strength and longitudinal reinforcement ratio on the vulnerability curve of high-strength reinforced concrete column is analyzed and discussed.