ELASTIC-PLASTIC ANALYSIS OF A LONG-SPAN CONCRETE FILLED STEEL-TUBE TRANSMISSION TOWER UNDER EARTHQUAKE ACTION
The elastic-plastic analysis of a long-span Concrete Filled Steel-Tube(CFST) transmission tower under earthquake actions is studied by the static method and the dynamic method,including: 1) fine FEM models of a CFST tower and a tower-line system are built and the nonlinear material models including steel-tube and CFST are also modeled.2) shear forces on supports obtained by a mode-decomposition response spectrum method are distributed at all nodes based on the structural first-order mode value and then the nodal loads increase step by step in order to impel materials into plastic status until calculation cannot converge.Static analysis shows there are some steel-tube elements failed but no any CFST element failed and the limit load is decided by the steel-tube elements.3) a seismic record is selected to analyze the seismic elastic-plastic behaviors of the tower by a time-history analysis method.The dynamic analysis shows a lot of elements enter the plastic status soon after earthquake action and there are some steel-tube elements failed but no any CFST element failed at last time,so the tower can achieve the goal: no collapse in the big earthquake.The two methods both show the weakest part is in the middle of the tower.