Mechanical behavior of lattice steel reinforced concrete inner frame with irregular section columns under cyclic reversed loading

A 1/2.5-scaled model of two-bay and three-story inner frames, which consisted of reinforced concrete beams and lattice steel reinforced concrete (SRC) irregular section columns, was constructed and tested under low cyclic reversed loading. Elasto-plastic features, integral and inter-story lateral stiffness degradation and the loading capacity of the structure were analyzed. Test results indicate that the lattice SRC inner frame has uniform lateral stiffness and the stiffness degradation process tends to be moderate. The relationship between story drift and the ratio of story stiffness degradation were obtained. The strength degradation appears to increase with the increment of displacement, but the effect is not obvious under the three cycles of each displacement level. The method of forming plastic hinge at the bottom of column is applicable for the calculation of story shear bearing capacity corresponding to the plastic moment of lattice SRC frame with irregular section columns. The elasto-plastic behaviors of the frame in positive and negative directions are similar. The ultimate elasto-plastic story drift rotation is larger than the limit value specified by the Chinese Code for The Seismic Design of Buildings (GB50011-2010), indicating that the capacity of collapse resistance of lattice SRC frame is higher. Compared with the reinforced concrete frame with irregular section columns, the ductility and energy dissipation capacity of lattice SRC frame structure are much better. The failure mechanism of the frame is the beam-hinged mechanism, which satisfies the seismic design principle of strong column and weak beam.