Seismic Behavior Of Steel Reinforced Concrete Frame With Dog-bone Type 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, dog-bone type 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 structure with dog-bone type reduced beam section are systematically performed, and the main research work and innovation achievements are included in the three aspects as following.(1) Experimental study and theoretical analysis on seismic behavior of beam-column joint of SRC frame with dog-bone type reduced beam sections. Through test of 7 full-scaled beam-column joint specimens under cyclic loading, the bearing capacity, ductility, energy dissipation and hysteretic characteristics of the beam-column joints of SRC frame with dog-bone type reduced beam sections are studied. The reliability of the dog-bone type reduced beam sections and prefabricated integral constitution is verified. The failure mechanism and damage performance of the beam-column joint and the function of the dog-bone type reduced beam sections on the bearing capacity of the beam-column joint are investigated. The results show that the beam-column joint of SRC frame with dog-bone type reduced beam sections has good ductility, strong deformation ability and high energy dissipation, therefore has advanced seismic behavior.(2) Experimental investigation and theoretical analysis on seismic behavior of SRC frame structure with dog-bone type reduced beam sections. Through test of a two-span, three-storey one-third scaled SRC frame model under cyclic loading, the bearing capacity, ductility, stiff degeneration, ability of energy dissipation, hysteretic characteristics, failure mechanism of the frame structure and the function of dog-bone type reduced beam sections on integral bearing capacity of frame are studied. The design method for seismic capacity of SRC frame structure is further investigated. The results shows that the SRC frame structure with dog-bone type reduced beam sections has good ductility, strong deformation ability and high energy dissipation and bearing capacity, so as to meet the requirement for the seismic behavior of general ductile frame.(3) Nonlinear finite element analysis on seismic behavior of SRC frame structure with dog-bone type reduced beam sections. According to mechanical characteristics of SRC, a constitutive relationship applied for SRC material under cyclic loading is built. Based on the above experimental investigation, employing the separated modulus theory and considering the influence of nonlinearity of material and geometry and rigidity degeneration and so on, the bearing capacity of beam-column joint and hysteretic characteristics of structure of the SRC frame with dog-bone type reduced beam sections under cyclic loading are investigated. The calculated results are much coincided with the tested results. This proves that the design method for SRC structure based on the separated modulus theory is feasible and applicable.