混凝土坝坝体配筋抗震措施研究

Plastic-damage analysis of concrete dams strengthened with reinforcement in monolith for seismic resistance

已有研究表明,对混凝土坝抗震采用线弹性分析得到的最大拉应力远大于混凝土的抗拉强度,在强震作用下,坝体将不可避免地产生开裂。本文以拉压应力损伤因子为内变量,采用混凝土塑性损伤模型,分析了坝体在地震荷载作用下的刚度退化以及在多维应力状态下拉应力引起的损伤破坏。在抗震措施方面,文中研究了塑性损伤模型的配筋模拟,并针对印度Koyna坝的震害情况,根据配筋前的塑性损伤分析,设置了两种不同的配筋方案,据此进行了塑性损伤动力分析,给出了配筋前后坝体的拉应力损伤因子分布及坝顶动位移响应。通过计算比较了配筋前后坝体的拉应力损伤因子分布范围及坝顶动位移响应,结果说明,配筋抗震措施能够明显地减小坝体损伤区的范围,显著限制坝体损伤区的扩展与贯穿,有效地改善了坝体的抗震性能。

The known studies indicate that peak tensile stress occurred at the upper portion of concrete gravity dam is much higher than the dynamic tensile strength of concrete during strong earthquake which resulted in the inevitably happening of cracking. In this paper, the stiffness degradation and damage failure in concrete dams subjected to strong ground motion are simulated by plastic-damage model based on damage index variable. A seismic resistance measure by adding reinforcement in monolith to strengthen the dam is suggested, and its effectiveness is verified by numerical modeling of the Koyna Dam, India. Two alternatives of reinforcement are to be considered. The comparison of calculation results shows that this measure can effectively reduce the damage zone and significantly control the extension of damage zone.