泊松效应对组合梁斜拉桥混凝土板纵向开裂的影响研究

摘要

To study the influence of Poisson effect on the internal force of concrete slabs of composite girder cable‐stayed bridge and examine the factors triggering longitudinal cracks in con‐crete slabs ,a composite girder cable‐stayed bridge with a main span of 480 m in China was taken as the study background .The finite element method was used to establish the spatial grid model (without accounting the Poisson effect ) and the plate and shell element model of the overall bridge (considering Poisson effect ) ,to analyze the Poisson effect of concrete slabs in composite girder from the view of elastic theory and calculate transverse stress and transverse strain in concrete top slabs respectively in the five segments at the top of the ancillary piers and the five segments at the four‐dividing point of the main span .The results of the calculation indicate that the longitudinal compressive stresses in the concrete slabs at the top of the ancillary piers and the four‐dividing point of the main span are great ,and the transverse stress of the concrete slabs in the two models is basically in the compressive stress condition .T he transverse strain of the concrete slabs calculat‐ed by the spatial grid model is basically compressive strain ,but that calculated by the shell element model is basically in the tensile strain condition ,approximate to the ultimate tensile strain w hen the concrete is in two‐way load bearing condition .The Poisson effect of the concrete top slabs of the composite girder is significant ,the transverse strain of w hich is the main factor triggering lon‐gitudinal cracks in concrete slabs .%为了研究泊松效应对组合梁斜拉桥混凝土板内力的影响，探究混凝土板纵向开裂的原因，以国内某主跨480 m的组合梁斜拉桥为工程背景，采用有限元法分别建立全桥空间网格模型（未考虑泊松效应）和板壳单元模型（考虑泊松效应），从弹性理论的角度探索了组合梁混凝土板的泊松效应，计算辅助墩墩顶5个节段和主跨四分点5个节段混凝土顶板的横向应力和横向应变。计算结果表明：在辅助墩墩顶及主跨四分点处混凝土板的纵向压应力较大，2种模型的混凝土板横向应力也基本处于压应力状态；按照空间网格模型计算得到混凝土板的横向应变基本为压应变，而按板壳单元模型计算得到的混凝土板的横向多处于拉应变状态，接近于混凝土双向受力状态下的极限拉应变；该组合梁混凝土顶板的泊松效应明显，其产生的横向应变是混凝土板纵向开裂的主要原因。