消除混凝土坝应力网格效应的三次等效应力法

Three-order Equivalent Stress Method for Eliminating Stress Grid Effect of Concrete Dam

针对混凝土坝有限元等效应力在角缘部位的失真问题,基于挡水结构的弹性力学解,提出一种改进三次等效应力法,即选取三次多项式模拟混凝土坝水平截面的正应力分布,确定多项式的待定系数,得到三次等效应力分布形式。以混凝土重力坝和拱坝为例,分别以线弹性有限元法、线性等效应力法、改进的三次等效应力法计算混凝土坝建基面的法向正应力和主应力,结果表明改进的三次等效应力法计算结果不仅有效减小了对计算网格的依赖性,且与线弹性有限元计算结果相当接近。结果可为混凝土坝的安全性评价提供参考。

The improved equivalent stress method is proposed to eliminate the effect of singular stresses at water barrier＇s heel and toe,which is based on the elasticity solution,assuming the normal stress of concrete dam＇s horizontal section is cubic polynomial distribution.According to the condition that the first three moment of improved equivalent stress should be equal to those of the stress from FEM,the coefficient of the polynomial can be obtained.Consequently,the distribution of improved equivalent stress can be achieved.The method was applied to gravity dam and arch dam.The stresses of foundation plane of gravity dam and the principle stress of arch dam are compared by using FEM,linear equivalent stress method and improved equivalent method.Case study shows that the results by improved equivalent method is closed to that of linear FEM,as well as effectively reduce the reliance on computing grid.Therefore,it provides reference for safety evaluation of concrete dam.