| Hollow flange beam(HFB) is a thin-walled bending member with unique cross section. The top and bottom flanges are two closed triangular steel tubes, middle web is a thin-walled steel plate. Due to the simple process and excellent performance, the HFB have been widely used in China and abroad. Rectangular steel tube flange beam is a new type of cross section beam which developed based on Australian hollow flange beam. Rectangular steel tube flange beam studied in this paper are divided into four cross sections: the top flange is rectangular steel tube and the bottom flange is steel plate, the top and bottom flanges are both rectangular steel tubes, in the other two cases, the top flanges are rectangular steel tubes filled with concrete to form thin-walled concrete filled steel tubular flange beams. The thin-walled concrete filled steel tube flange beam can give full play to the mechanical properties of concrete and steel, respectively. The presence of concrete can also avoid the occurrence of local buckling for steel tube, so as to improve its bearing capacity.The main work of this paper are as follows:1. The bending capacity experiments of three simply supported rectangular steel tube flange beams are finished which are applied concentrated forces on middle span. The failure mode, stress-strain relationship for section and load-displacement relationship for the top and bottom flanges of three different types of rectangular steel tube flange beams are analyzed and studied, and then, the ultimate bearing capacity of three specimens are got.2. According to the neutral axis position of different sections, the theoretical calculation formula of elastic bending bearing capacity and plastic ultimate bending bearing capacity of four kinds of sections simply supported concrete filled rectangular steel tube flange beams is derived. Considering the two kinds of core concrete constitutive relationship respectively, the comparation and anslysis of elastic bending bearing capacity of two kinds of sections concrete filled rectangular steel tube flange beams are conducted. Using superposition theory and unified theory of concrete filled steel tube, plastic ultimate bending bearing capacity of two kinds of sections concrete filled rectangular steel tube flange beams is compared and analysed.3. Using finite element analysis software ABAQUS and selecting suitable constitutive relationship for concrete and steel with considering the material nonlinearity, static simulation analyses for rectangular steel tube flange beams of four different cross sections are conducted. Then the bending moment- curvature curves(M-Φ)of four members are got. The correctness and applicability of the theoretical formulas and finite element analysis methods are verified by comparing theortical, experimental results with finite element results of four kinds of rectangular steel tube flange beams. |
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