Seismic Capacity Design And Nonlinear Analysis Of Steel Reinforced Concrete Frame With Reduced Beam Sections

Compared with reinforced concrete (RC) structure, steel reinforced concrete (SRC) structure has characteristics of high bearing capacity and good ductility, so has been applied in engineering widely. However, under action of strong earthquake, plastic hinge at beam end may induce brittle fracture of welded joint between beam and column and entry joint core, which may reduce the seismic behavior of the SRC structure significantly. In this dissertation, reduced beam section is proposed for steel flanges at beam end so as to transfer the plastic hinge from the beam end to the reduced section. This may improve the seismic behavior of the SRC structure, and has important significance in theory and value in engineering.In this dissertation, the experimental investigation and theoretical analysis on seismic behavior of SRC frame with reduced beam sections are systematically performed, and the main research work and innovation achievements are included in the three aspects as following.(1) The experimental research on the seismic behavior of the steel reinforced concrete frame with reduced beam sections. Based on the Code recommendations an experiment on the SRC frame with reduced beam sections was performed under cyclic loading, the results of the experiment shows a beam joint damage mechanism. The deformation capacities, bearing capacities, ductility, energy dissipation capacities satisfied the seismic requests. The model frame positive ductility factor reaches 7.34 and the negative one reaches 7.4 which is satisfy the request of superior to 4 for the ductility factor of ordinary ductile frame.(2) Elastic-plasticity analysis of the steel reinforced concrete frame with reduced beam sections.Trough the push-over analysis of the experiment specimen frame, the obtained occurrence sequence of the plastic hinges and the members'failure are quite similar to experiment results. Based on that, parameters of the SRC frame has been modified to obtain many analysis cases. The occurrence sequence of each case plastic hinges and the frame seismic characteristics such as shear curve, bearing capacity, displacement ductility and failure mechanism comparison of the push-over analysis results showed: Beams and columns flexural strength ratioη,axial-compression ratio n and the reduced beam section cut depth c are the three main parameters that influence the failure mechanism of SRC frame with reduced beam sections. (3) Nonlinear finite element analysis of SRC frame with reduced beam sections. Based on the reactions characteristics of steel reinforced concrete, we establish the constitutional relationship of the steel reinforced concrete materials under cyclic loading. Considering the influence of non-linear, geometric non-linear and rigidity degradation factors, a numerical modeling with APDL program has been made to analyze the reactions capacities of the steel reinforced concrete frame under the cyclic loading. The comparison with the model experiment results shows that the two analyses are mostly identical which verify the feasibility and application of finite element to analyze steel reinforced structure.