中文摘要：

为研究考虑截面配筋后的混凝土箱梁在开裂状态下的剪力滞效应，基于变分原理建立了考虑截面配筋率的箱梁剪力滞效应分析的控制微分方程，并推导出箱梁开裂前后的微分方程表达式。结合具体箱梁算例，分析了2种不同配筋率的箱梁在不同荷载作用下开裂前后的剪力滞效应。结果表明:集中荷载或均布荷载作用下，初始开裂截面及集中荷载作用截面剪力滞效应均发生突变;配筋率对开裂状态箱梁的剪力滞效应的影响大于其对于未开裂状态箱梁的影响;2种状态下最大影响位置均为初始开裂截面，剪力滞系数变化最大可达10.31%。

英文摘要：

To study the shear lag effect of concrete box girder with section reinforcement bars after cracking,based on variation principle the governing differential equations for shear lag effect analysis considering section reinforcement ratio were established,and the differential equations before and after box girder cracking were derived.Combining with the calculation example of a box girder,the shear lag effect with two different reinforcement ratios under different loads were analyzed.The results show that the shear lag effect of box girder has sudden change at the initial cracking section and the concentrated load action section under concentrated load or distributed load.T he influence of reinforcement ratio on the shear lag effect of cracking box girder is greater than that of non-cracking box girder.T he maximum influence position is at the initial cracking section in the two states.T he maximum variation of shear lag coefficient can be up to10.31%.