波形钢腹板(钢腹杆)-混凝土组合箱抗扭承载力试验与计算

为研究波形钢腹板（钢腹杆）-混凝土组合箱抗扭特性，进行了构件的抗扭承载力试验，结果表明:混凝土底板首先出现斜向裂缝，裂缝与混凝土主拉应变垂直，顶底板裂缝呈螺旋状开展，裂缝方向与主梁纵轴线约成45°；底板出现宽度较大的主斜裂缝，钢筋受拉屈服，组合箱受扭破坏。采用有限元软件ANSYS对扭转试验构件进行了非线性有限元分析，有限元分析结果与试验结果吻合良好。参照混凝土箱梁的开裂扭矩计算公式，建立了组合箱开裂扭矩的计算公式；应用混凝土箱梁变角度空间桁架理论，根据波形钢腹板（钢腹杆）-混凝土组合箱达到极限扭矩时可能出现三种破坏形式，建立了组合箱极限扭矩的计算公式。通过与试验结果和实桥截面有限元分析结果的比较表明，建立的波形钢腹板（钢腹杆）-混凝土组合箱抗扭承载力简化计算公式具较高精度，最大误差不超过10%，可运用于实桥计算。

EXPERIMENT AND CALCULATION ON TORSION BEARING CAPACITY OF CONCRETE COMPOSITE BOX SECTION WITH CORRUGATED STEEL WEBS AND STEEL TRUSS WEBS

To investigate the torsion behavior of concrete composite box sections with corrugated steel webs and steel truss webs, the torsion bearing capacity experiments were carried out. It is found that the diagonal cracks, perpendicular to the principal tensile strains of concrete, first appeared at the bottom plate. Then the cracks spirally developed at both the top and the bottom plates, and the angle between the cracks and the longitudinal axis of the main girder was approximately 45 degrees. Eventually, some larger diagonal cracks were observed at the bottom plate, and the specimens failed by torsion damage after steel rebar yielded in tension. The nonlinear finite element analysis (FEA) for torsion test specimens was simulated using finite element software ANSYS, and the results obtained by FEA agreed well with test results. The cracking torque formula of composite box sections was proposed with reference to the formula of concrete box girders. Using the variable-angle spatial truss model for concrete box girders, the formula of the ultimate torque for composite box sections was established according to the three probable torsion failure modes. In comparison with the results of model test and finite element analysis for actual structural size, the proposed formulas of torsion bearing capacity of concrete composite box sections with corrugated steel webs and steel truss webs had high accuracy, and the maximum error was less than 10%. The proposed formulas can be applied in practical bridge calculation.