大坝矩形孔口应力状态分析

Analysis on the stress conditions of rectangular openings of dam

大坝孔口混凝土中的钢筋只有在混凝土开裂后才真正起作用。为使钢筋布置更为有效 ,需找出孔口开裂后拉应力分布规律。用线弹性计算的拉应力区 ,在坝体自重作用时出现在孔顶中部 ;在内水压力作用时出现在角缘 ;两者叠加后 ,最大应力出现在角缘附近。而非线性计算中 ,钢筋应力明显较大 ,最大应力只出现在裂缝处。分析认为 ,坝体自重是引起拉应力的主要因素 ,内水压力和温降主要引起角缘附近的拉应力 ,而且会加剧应力集中。非线性有限元计算能比较真实地反映孔口受力特性 ,使配筋设计更为合理、有效 ,但在混凝土本构关系。

The steel bar in the concrete of dam opening functions only when concrete cracks It is necessary to discover the laws of tensile stress distribution of the cracked opening in order to make steel arrangement more effective By using the linear elasticity method to calculate the tensile stress zone, it is found that the maximum tensile stress occurs in the middle position of opening top under the action of self weight of dam body or in the edge of opening under the action of internal water pressure So the actual maximum tensile stress will occur in the near of the edge of opening under the action of the self weight of dam body and the internal water pressure But through non linear calculation, it is found that the stress of steel bar is bigger and the maximum tensile stress occurs in the crack position It is considered through analysis that the self weight of dam body is the main factor causing tensile stress and the internal water pressure and temperature drop produce the tensile stress in the edge of opening that will increasingly concentrate the stresses The non linear finite element calculation can more really reflect the characteristics of stress of opening to make the design of reinforcement more reasonable and effective But the relation of the origin and component of concrete, the bonding relation of steel bar and concrete, and the simulation of crack width should be further perfected