The shear lag of the box girder section of a wide box bowstring arch bridge was investigated in this study. The finite element analysis software Midas Civil was used to discretize the bridge into separate entities, establish its spatial model, and analyze the law of shear lag effect in the longitudinal direction during the main construction stage and the completion stage separately. The shear lag effect is more prominent at certain key points due to the influence of the tension of the boom and the weight of the arch foot during the construction stage. After the bridge is completed, the axial pressure of the arch foot drives the shear lag effect near the midpoint of the main girder section to its maximum; the axial force is transmitted along the longitudinal bridge direction in a V shape along which it gradually decreases. Under the action of uniformly distributed load, the cross-section of the box girder near the middle fulcrum is affected by the axial force of the arch foot; there is both a positive and negative shear lag effect. Under the eccentric load, the positive and negative shear lag effects appear simultaneously at the end fulcrum. The shear lag coefficient is higher in the web on the eccentric load side than the non-load side. There is obvious and widely fluctuating positive/negative shear lag effect in the vicinity of the middle fulcrum. There is significant tensile stress on the roof under the action of the middle fulcrum. The cross-sectional stress of a single-box seven-cell box girder under compression-bending load action was analyzed according to the finite element analysis results. The stress was decomposed into a superposition of bending moment action and axial force action. The shear lag coefficient ${\lambda }_M$ under the action of bending moment was also solved via energy variation method. Assuming that the axial force is only borne by the compressed area, the shear lag coefficient ${\lambda }_N$ under the action of the axial force was obtained; ${\lambda }_M$ and ${\lambda }_N$ were superimposed to determine the comprehensive shear lag effect coefficient $\lambda$.

在这项研究中，研究了宽箱形弓弦拱桥箱形梁截面的剪力滞后。使用有限元分析软件Midas Civil将桥梁离散化为单独的实体，建立其空间模型，并分别在主要施工阶段和竣工阶段分析纵向的剪力滞后效应规律。在施工阶段，由于动臂的张力和足弓的重量的影响，剪力滞后效应在某些关键点更加突出。桥梁完工后，足弓的轴向压力将主梁中点附近的剪力滞后效应驱动到最大。轴向力沿纵向桥方向以V形传递，沿该V形逐渐减小。在均布荷载作用下，箱梁中支点附近的横截面受到足弓轴向力的影响。既有正的剪切滞后效应又有负的剪切滞后效应。在偏心载荷下，正和负剪切滞后效应同时出现在末端支点处。腹板在偏心载荷侧的剪切滞后系数高于无载荷侧。在中支点附近有明显且波动很大的正/负剪切滞后效应。在中间支点的作用下，屋顶上会产生很大的拉应力。根据有限元分析结果，分析了单箱七格箱形梁在压弯荷载作用下的截面应力。应力被分解为弯矩作用和轴向力作用的叠加。剪切滞后系数${\lambda }_{\mathrm{中号}}$在弯矩作用下也通过能量变化的方法解决了。假设轴向力仅由压缩区域承担，则剪力滞后系数${\lambda }_{ñ}$ 在轴向力的作用下获得； ${\lambda }_{\mathrm{中号}}$ 和 ${\lambda }_{ñ}$ 叠加以确定综合剪切滞后效应系数 $\lambda$。