钢管混凝土柱组合梁框架的抗火性能研究

Jingxuan Wang, Wenda Wang, Zhongmao He School of Civil Engineering, Lanzhou University of Technology, Lanzhou 730050, P.R. China
Abstract: This paper presents a finite element analysis(FEA) model of concrete-filled steel tubular(CFST) columns to steel beam frame with RC slab to investigate the fire performance and provide reasonable fire resistance design method based on ABAQUS. The reasonable thermal and material models were chosed in the FEA model. Due to lacking of experimental datas about the fire behavior of composite frame, the FEA model results were verified by the fire performance of CFST columns to composite beam joint and CFST columns to RC beam frame experiments, respectively. Typical failure modes and displacement of beam and column versus fire time relationships were studied to calculate the fire resistance of the frame. The results show that the fire duration time of composite frame is increased significantly with the increased of the thickness of fire protection and decreased the fire load ratio of columns. The fire resistance of composite frame columns is larger than the single columns due to the absorption of heat and the constraint function of the reinforced concrete slab. Keywords: CFST columns to composite beam frame, fire resistance, finite element analysis(FEA) model, factors analysis
The 12th International Symposium on Structural Engineering
PRELIMINARY RESEARCH ON FIRE RESISTANCE OF CONCRETE-FILLED STEEL TUBULAR COLUMNS TO COMPOSTE BEAM FRAME
columns in a complete fire stage including cooling process under axial load. Wang et al.(2012) reported the mechanical performance of CFST columns subjected to full stage fire under axial load, eccentric load and bending load based on ABAQUS. Huo et al.(2010) presented the experimental results and finite element analysis of eight specimens of repaired concrete filled steel tubular columns to steel beam joints after exposure to fire. Song et al.(2010) tested three concrete filled steel tubular columns to steel beam joints with RC slabs under loading and fire. Tan et al.(2012) reported threedimensional FEA model of typical-full scale CFST column to RC beam joint in fire, which the slip between steel bars and concrete was considered. Little theoretical and experimental research, however, has been done to investigate the fire resistance and fire performance of composite frame with CFST columns. Han et al.(2010) reported six tests on reinforced concrete beam to CFST columns planar frames with RC slab subjected to ISO-834 standard fire. Based on this experiment, Han et al.(2012) performed theoretical investigation on the fire performance of these frames. From above, there is little reports about fire resistance of CFST columns to steel beam planar frame with RC
2.1 Temperature Field Analysis
The temperature field model of concrete filled steel tubular columns to composite beam frame was established by choosing reasonable steel and concrete thermal parameters and the boundary conditions which followed ISO-834 standard fire curve. Thermal conductivity coefficient, specific heat and desity of concrete and steel were defined in the heat transfer model. In the thermal analysis, steel tube, concrete, steel beam and RC slab are modelled using 8-node brick elements(DC3D8) and 2-node heat transfer link element(DCID2) is used for rebar. The steel tube and core concrete of frame columns, stud and beam, RC slabs and flange of beam are all connected with *TIE command, relative slip is not taken into consideration among them. The effects of heat convection and radiation are included as boundary conditions and heat transfers from air to frame during heating stage. In order to transfer accurately temperature of nodes and elements to mechanical analysis model, “NODE FILE, ENTER NT” command must be written in the input FILE(*.inp). 2.2 Mechanical Aanalysis Model
slab. This paper will develop a FEA model of this frame to investigate the fire resistance and deformation and failure mechanism based on ABAQUS.
2 THE FINITE ELEMENT ANALYSIS MODELFire can bring serious threat to person′s life and property. The research on the fire resistance of architecture structures is beneficial to maintain their safety and prevent their collapse when exposure to fire. In recent years, Concrete-filled steel tubular structures have been widely used in practical structure due to the favorable composite characteristics of steel and concrete materials which providing the merits of higher strength and stiffness, higher fire resistance than bare steel structure for concrete filled and better fire performance than reinforced concrete structure as the tube casting prevents spalling of the concrete(Han, 2007). It has important theoretical significance and practical value to invenstigate the fire performance of concrete filled steel tubular structure exposure to fire. Up until now, a large number of research results on fire performance of concrete filled steel tubular members and joint with CFST column have been done, including exposure to overall stage fire. Such as Yang et al.(2008) reported the analysis of concrete filled steel tubular columns after exposure to overall stage fire. Song et al.(2010) developed a FEA model to investigate the behaviour of CFST stub