Nonlinear Analysis Of Axially Compressed Concrete Steel Tube Composite Columns Filled (CFST) Under Fire

Fire resistance of structures is an important subject in structural engineering. Currently, the research on fire-resistant performance of reinforced concrete columns concrete filled steel tubular columns and steel reinforced concrete columns have been already carried on by domestic and international. The concrete filled steel tube(CFST) composite columns as a new types of composite columns be studied more late,and studies on mechanics performance under normal temperature. primarily ,Therefore,the research of mechanics performance under fire and after fire be more seldom seen. Along with our country high building of quick development, the better exertive space will be provided to a kind of new types of composite columns, the mechanics performance under fire be studied is extremely essential.According to this kind of purpose, the former related subjects firstly are summarized in this article, the finite element modeling of CFST composite columns is created by the finite element software of ansys, temperature field of CFST composite columns and ultimate lode bearing capacity are analyzed. The main work is as follows:(1) The most familiar thermal and mechanical behaviors of concrete and steel at elevated temperature over the world are summarized and compared. The thermal and mechanical parameter is fixed for this thermal analysis and thermal-mechanic coupling calculation.(2) The methods to calculate the temperature field of section are summarized, the surface effect elements are created in the CFST composite columns surface, and the nodes are established around CFST composite columns, which be used to imitates between fire source and sureface of column thermal transmission.;Based on this foundation,The effects of different parameters such as burning time, surfaces exposed to fire, thickness of steel tube, dimensions of cross section and position coefficient on the temperature field are analyzed.(3) The ultimate lode bearing capacity is analyzed about the axial pressing of CFST under the fire, and the reduction coefficient is calculated, influencing parameters such as burning time, dimensions of cross section, characteristic value for providing stirrup, steel ratio, reinforcement ratio, yield strength of steel tube, position coefficient and axial compressive strength of concrete are discussed in detail.