基于混凝土塑性损伤模型的桥墩在快速水流作用下的损伤分析

Damage Analysis of Pier Under the Action of Rapid Water Flow Based on Concrete Damaged Plasticity Model

为探究快速水流作用对桥梁水下结构的影响,基于混凝土塑性损伤模型,建立了某桥墩在水流压力作用下的有限元分析模型,系统分析了不同水流速度、水深条件下不同强度桥墩结构变形及损伤的发生、发展过程及特征。结果显示,快速水流作用下,桥墩根部迎水面的受拉区更容易发生损伤;考虑结构非线性后,桥墩的水位高度临界值在8m左右,水流速度的临界值在6m/s左右;超过临界值后桥墩的塑性损伤及墩顶位移发展急剧加快,在一定条件下会超过规范限值。计算结果还表明,对同一个桥墩而言,损伤发生时的预警流速仅为按照规范规定的墩顶位移限值确定的预警流速的0.6倍左右,故目前传统设计的桥梁存在一定的损伤隐患;而提高混凝土强度并不能显著提高预警流速,将混凝土强度从C25提高到C40,预警流速仅增加了10%。

In order to explore the impact of rapid water flow on bridge underwater structure,based on the CDP(Concrete Damaged Plasticity)model,a finite element analysis model of a bridge pier under the action of water pressure was established,and the occurrence,development and characteristics of deformation and damage of bridge pier structure with different strength under different water velocity and water depth were systematically analyzed.The results show that under the action of rapid water flow,the tensile zone of the upstream surface of the pier root is more likely to be damaged.Considering the structural nonlinearity,the critical value of the water level height of the pier is about 8m,and the critical value of the water flow speed is about 6m/s.When the critical value is exceeded,the plastic damage of the pier and the pier top displacement develop rapidly,and under certain conditions,they will exceed the specification limit.The calculation results also show that,for the same pier,the early-warning flow rate when damage occurs is only about 0.6 times of the early-warning flow rate determined according to the pier top displacement limit specified in the specification.Therefore,there is a certain potential damage risk in the traditional bridge design.However,improving the concrete strength does not significantly improve the early-warning flow rate.When the concrete strength is increased from C25 to C40,the flow rate has only increased by 10%.