钢板组合桥梁剪力滞效应分析

Analysis of shear lag effect of steel-concrete composite continuous bridge girder

双肋钢板组合桥梁(双钢板主梁与砼桥面板通过剪力钉连接)由于主梁间距大而存在明显的剪力滞效应。文中选取三跨双肋钢板组合连续桥梁(3×35 m)作为研究对象,采用ANSYS建立其有限元模型,分别对给定温度环境下受恒载和车道荷载作用的桥面板应力进行分析,计算其剪力滞系数。按最大正应力和合力大小不变的原则,将呈曲线分布的正截面应力简化成矩形分布,计算桥面板的有效宽度,并与规范计算结果进行对比。研究结果表明:在恒载和车道荷载作用下,中支点处存在显著的正剪力滞效应,剪力滞系数可达到1.7左右。在中跨和边跨其余各截面均存在负剪力滞效应。从边支点截面到中支点截面由负剪力滞效应逐步向正剪力滞效应过渡,从中支点截面到中跨跨中截面则由正剪力滞效应逐步向负剪力滞效应过渡。与有限元方法相比,按照规范方法计算的边跨跨中和中跨跨中截面的桥面板有效宽度偏于保守,中支点截面按规范方法计算的有效宽度偏于不安全。

The double rib steel-concrete composite bridge girder has obvious shear lag effect due to large spacing of its main girder.In this paper,a three-span double rib steel-concrete composite continuous bridge girder(3×35 m)was selected as the research object.The finite element model established by ANSYS was used to analyze the concrete deck stress under dead load and vehicle load respectively,at a given temperature environment,with the shear lag coefficient calculated.According to the principle of constant maximum normal stress and resultant force,the longitudinal stress of the curve distribution was simplified to rectangular distribution,and the effective width of the concrete deck was calculated followed by a comparison with the specifications calculation results.A detailed analysis show that,under self-weight and vehicle load,there is a significant positive shear lag effect at the middle fulcrum,and the shear lag coefficient can reach about 1.7.There are negative shear lag effects in the remaining sections of the middle span and the side span.From the side fulcrum section to the middle fulcrum section,the negative shear lag effect is gradually changing to the positive shear lag effect.And from the middle fulcrum section to mid-span section in the middle span,the positive shear lag effect gradually changes to the negative shear lag effect.The concrete deck effective width of the mid-span section in the side span and mid-span section in the middle span calculated by specifications,rather than the finite element method is conservative,with the effective width unsafe of the middle fulcrum section.