利用有限元方法对方中空夹层钢管混凝土和方实心钢管混凝土压弯扭构件的受力全过程进行计算，对比分析该两种构件的工作机理。分析结果表明，在压弯扭受力状态下，方中空构件与方实心构件抗扭承载力相当，方中空构件的延性优于方实心构件；截面角部处外钢管与混凝土的相互作用力远大于截面中部处的；两种构件的钢管与混凝土分别承担的纵向荷载与纵向应变关系曲线的整体变化趋势大致相同；方中空构件的内外钢管承担的扭矩大于方实心构件钢管承担的扭矩，夹层混凝土承担的扭矩小于核心混凝土承担的扭矩；由于钢管对混凝土的约束，使得混凝土承担了26%～33%的扭矩，而混凝土的存在阻止了钢管屈曲的产生。%Finite element method is adopted to analyze mechanism of the concrete-filled double skin steel tube (CFDST)and concrete-filled steel tube(CFST)members. The outer steel tube of CFDST and CFST members is square hollow section(SHS),and the inner steel tube of CFDST member is circular hollow section(CHS). This study finds that the ultimate bearing capacity of CFDST under combined compression-bending-torsion load is in accordance with CFST,but the ductility of the CFDST is better. The interaction between steel and con-crete in the corner is the largest in the cross section. The longitudinal loads born by steel tubes and concrete of CFDST and CFST versus longitudinal strain relationship curves are substantially the same. The torque born by steel tubes of CFDST is more than that of CFST,and the torque borne by sandwiched concrete of CFDST is less than that borne by core concrete of CFST. The concrete bears 26%~33%torque of the member due to the con-straint of steel tubes and prevents the buckling of steel tubes.
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