变截面波形钢腹板组合箱梁剪应力计算研究

Research on shear stress calculation in variable cross-section of composite box girder with corrugated steel webs

为研究变截面波形钢腹板组合箱梁腹板的剪应力计算和承剪比问题,考虑梁底线形变化,选取一个变截面微元段进行受力分析,计入弯矩、剪力和轴力的共同作用,推导变截面波形钢腹板组合箱梁的腹板剪应力计算的通用公式,方便工程应用。为验证公式的准确性,结合一座实际工程,分析集中荷载和自重作用下有限元结果与通用公式计算值的差别,由此获得腹板承剪比例。研究结果表明:通用公式计算结果与有限元结果吻合良好,剪应力计算中变截面效应引起的"附加剪应力"不可忽视;同时钢腹板承剪比受梁底线形变化的影响较大,越靠近根部截面,随着梁底线形指数n的增加,钢腹板承剪比下降迅速;梁底线形采用1.8次和2次抛物线时,在自重作用下,根部截面腹板承剪比在50%左右,与简化计算方法相比腹板的强度和稳定均有很大富余,明显偏于保守。

In order to study the shear stress calculation and shear ratio of the webs of the variable section corrugated steel web composite box girder, considering the change of the shape function of the beam bottom edge, a variable section micro-element was selected for force analysis. Bending moment, shear force and axial force are taken into account. A general formula for calculating the web shear stress in variable cross-section of composite box girder with corrugated steel webs was derived, which is convenient for engineering applications. For verifying the accuracy of the formula, combined with an actual engineering, and comparing the finite element results to the general formula calculated value under the concentrated load and the self-weight, the web shear ratio was obtained. The results show that the calculated results of the general formula are in good agreement with those of the finite element method, and the ‘additional shear stress’ caused by variable cross-section effect should not be neglected in the calculation of shear stress. Besides, the shear ratio of steel webs is greatly affected by the change of the beam bottom edge, and the closer to the root section, the faster the shear ratio of steel webs decreases with the increase of the bottom line index n of the beam. When the beam bottom line adopts 1.8 times and 2 times parabola, the shear ratio of the web section of the root section is about 50% under the self-weight. Compared with the calculation of the simplified method, the strength and stability of the web has a big margin, which is obviously conservative.