Seismic behavior of steel reinforced concrete column–steel truss beam hybrid joints

A research program on seismic behavior of steel reinforced concrete column–steel truss beam hybrid joints is carried out to support the design of the New China Science & Technology Museum built at Beijing City. Reversed cyclic loading tests on four specimens are first conducted to intensively investigate the seismic behavior of the hybrid joint. The load–displacement curves, shear behavior of the joint core, strength and stiffness degradations, ductility, energy dissipation capacity, deformation characteristics, etc. of the test subassemblies are analyzed. Two different failure modes can be observed in the tests, and the joints with flexural failure at the beam end illustrate higher stiffness and strength, better ductility and energy dissipation capacity than those with shear failure at the joint core. As a result, rational control of the failure mode is one of the most effective ways to enhance the seismic behavior of the joint. Based on the experimental observations, a design formula for shear strength of the joint core is derived using the shear model including the inner concrete compression strut, outer concrete compression strut and steel web panel shear mechanisms, and an analytical method for controlling the failure mode of the joint is also presented. Finally, the proposed method in this paper is verified by the experiment results and compared with other available methods provided in the current design codes and the literature.