Research On Mechanical Performance Of Reinforced Concrete Column Based On Buckling Restrained Reinforcements

The survey finds often the plastic hinge happened at the end of columns after the earthquake,concentrated embodying in compressive buckling of longitudinal reinforcements and crushing of the core concrete.The buckling of longitudinal reinforcements is particularly serious in some old structures because of not carried out in accordance with the ductility seismic design method.Although more transverse reinforcements at the plastic hinge are provided in now structural design,it is hard to avoid buckling of longitudinal reinforcements.In addition,too many transverse reinforcements may cause the internal reinforcements crowded and difficulty in casting concrete.Once serious buckling of longitudinal reinforcements is happened in RC columns,the bearing capacity drops rapidly,also causing the difficulty to repair after the earthquake because of the plastic deformation of longitudinal reinforcements.At present,the study of domestic and foreign scholars has confirmed that buckling of longitudinal reinforcements would make degradation of bearing capacity,but to prevent the buckling of longitudinal reinforcements is still a lack of research,especially reports about development of the buckling restrained reinforcements are very rare.To complete the study of buckling of longitudinal reinforcements,the factors of buckling of longitudinal reinforcements was analyzed on the basis of study home and abroad;A buckling restrained reinforcement was developed,and the axial compressive and cyclic beheavior was carried out.Axial compressive test on RC Columns with buckling restrained reinforcements was carried out.A fiber element numerical modeling method is presented considering the buckling behavior of longitudinal reinforcements.The research work of this paper mainly includes:(1)The numerical simulation analysis considering the buckling behavior of reinforcements is carried out based on ABAQUS software.A entity finite element numerical modeling method considering the buckling behavior of reinforcements is presented,and the influence of the rebar diameter,yield strength,length to diameter ratio(L/D),and the loading way.The study have shown that axial compressing behavior of longitudinal reinforcement bars only depends on the L/D parameter,cyclic loading behavior is influenced by loading history,plastic deformation,cumulative damage and L/D.(2)A buckling restrained reinforcement was developed,its mechanical performance under axial compressive and cyclic loading was studied,and the test results are analyzed in the numerical simulation.A normalized stress-strain relationship considering influence of length of restrained collars on the stiffness of reinforcements after yielding based on experiment and numerical simulation analysis results.(3)RC columns of C10 and C30 concrete with buckling restrained reinforcements were tested under axial compression,verifying the effectiveness of proposed buckling restrained reinforcement can improve the ductility performance of reinforced concrete column.(4)A fiber element numerical modeling method was presented considering the buckling behavior of longitudinal reinforcements based on the Meakawa constitutive model considering buckling in OpenSees finite element software,the modeling method was verified through the UW-PEER database test,and considering the influence of axial compression ratio on the buckling of longitudinal reinforcements.