| With the rapid development of civil engineering in China, civil engineering structures are heading towards large-scale and diversification. The situation that general strength steel is as the main material of reinforced concrete structures have been unable to meet the above requirements to achieve energy saving and emission reduction, green environmental protection and sustainable development of civil engineering. It has become an urgent task that developing low-cost high-performance reinforcement and study on its engineering applications. Beam-column joints which are widespread in buildings, bridges and other civil engineering structures are important components to ensure the structures work in integrality. The beam-column joints endure horizontal shear, vertical shear and bending moment under seismic action. The mechanical behavior of beam-column joints are quite complex. It is difficult to repair once the beam-column joints suffer damage. Study on the seismic performance of concrete beam-column joints reinforced with HRB500E high-performance steel bars in China is still in blank stage. therefore, it is necessary to conduct in-depth study on the seismic performance of high-performance reinforced concrete beam-column joints.In this paper, the pseudo-static test was conducted on three specimens of high-performance reinforced concrete beam-column joints. The beam-column joints were reinforced with HRB500E high-performance steel bars which were developed by Shougang Shuicheng Iron&steel(Group) Co., Ltd. The engineering feasibility, advantages and seismic performance of the beam-column joints reinforced with high-performance reinforcement were focused on. The characteristic values of beam-column joints seismic performance, such as beam end force-displacement hysteretic curves, skeleton curves and ductility factor were obtained through the experiment. The influence of beam reinforcement ratio and joint stirrup ratio on the seismic performance of high-performance reinforced concrete beam-column joints was studied.It can be seen that the high-performance reinforced concrete beam-column joints under low frequency reversed loads showed good ductility and energy dissipation performance according to the test phenomenon and characteristic values of seismic performance. The beam-column subassemblages can meet seismic design requirements. Increasing Beam reinforcement ratio can significantly improve the yield load and ultimate load of beam-column joints, but will increase the yield displacement of beam-column joints, and reduce beam-column joints’ductility. With the increase of the joint core stirrup ratio, the shear stiffness of beam-column joints is increased, and the yield displacement of beam-column joints is decreased, thus the ductility of beam-column joints is increased. Increasing joint core stirrup ratio can also improve the energy dissipation performance of beam-column joints. The smaller stirrup spacing of the joint core is, the smaller shear crack width and spacing is. through experimental Phenomenon, constant axial compression force on the top of column can delay joint core cracking, and deviate the cracking direction toward column axis. It can be found that the smaller beam bar diameter is, the better the performance of its bond and anchor is, by comparing the bond slip of beam bars through the joint for three specimens. The yield strength of High-performance reinforcement which is used as joint core stirrups can be fully exerted. Chinese code "Code for design of concrete structures"(GB50010-2010) specifies that when transverse reinforcement is used as shear reinforcement, its should take360MPa if it is greater than360MPa, while the tensile strength design value of HRB500E high-performance steel bars is435MPa. It can be seen that the code specification is too conservative, which may cause the amount of joint core stirrups excess, resulting in unnecessary waste of resources and the difficulties of construction.Disturbed Stress Field Model (DSFM) was obtained by improving the Modified Compression Field Theory, which can consider the effect of crack shear slip. is mainly used in the shear analysis of the stress turbulence district for the reinforced concrete (RC) element. The shear behavior analysis of reinforced concrete shear panels was conducted by the self programming based on DSFM. The shear strength of the shear panels was attained. Good agreement between the prediction results and the test results was achieved with an average ratio of the prediction results to the test results of1.16and a variance of0.11. Thus the accuracy and reliability of the self programming were validated. The shear behavior analysis of RC beam-column joints was conducted by the self programming based on DSFM. The obtained shear stress-strain relationship and shear strength of beam-column joints were compared with the experiment results. For the shear stress-strain relationship of beam-column joints prediction results was agreed well with the experiment results. For the shear strength of beam-column joints good agreement between the prediction values and the test values was achieved with an average ratio of the prediction results to the test results of0.87and a variance of0.23. The self programming based on DSFM is suitable for the shear behavior analysis of RC beam-column joints.Finite element models (FEMs) of high-performance and ordinary reinforced concrete beam-column joints were established using OpenSees. the parameters for shear panel component of the model beamColumnJoint element in the FEMs. can be set by the self programming based on DSFM. The simulation results were compared with the experimental results by numerical calculating. The beam end force-displacement hysteretic curves are in good agreement, which validates the use of numerical analysis method is reasonable, accuracy and versatility. Then parametric analysis was carried out on the high-performance reinforced concrete beam-column joints. The influence of beam reinforcement ratio, joint stirrup ratio and axial compression ratio on the seismic performance of the high-performance reinforced concrete beam-column joints were studied respectively. |
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