Analysis Of Spatial Nonlinear Earthquake Responses Of Reinforced Concrete Frame Structures

Based on finite element method(FEM), a new spatial numerical model for nonlinear responses of reinforced concrete(RC) frame structures under 3-dimensional earthquake is proposed: The 3D FEM model for RC frame strucutres is composed of bar elements which represent beams and columns, and lumped mass is concentrated at the node of bar elements. By adopting variable stiffness element model, each bar elment is divided into three parts: two elasto-plastic zones at the two ends of the element and one elastic zone in the middle, which could take into account the stiffness change along the element. Borrowing ideas from the multi-spring model, the section in the elasto-plastic zone is divided into some steel springs and concrete springs which represent steel bars and concrete, and the constitutive relations with failure criterion for springs is defined to consider the tensile, compressive, bending behavior of the elements. During analysis, the stiffness of material in the elasto-plastic zones is changing as the displacement varies, and by the variable stiffness model the change can be expressed in the stiffness matrix of the bar element. Based on the proposed model, a software system is developed to simulate spatial responses of RC frame structures on the Visual C++ development platform. Verifying the simulation system by shaking table tests of two RC frame structures and other analysis examples covering structures under single-dimensional earthquake wave, two-dimensional earthquake wave and three-dimensional earthquake wave, the original structure of the model in test, it can be concluded that the simulation system can commendably simulate the nonlinear responses of RC frame structures by choosing appropriate hysteresis models under arbitrary routes of loading. The simulation system developed here can be used as an assistant tool for design of new building structures and assessment of existing building structures.