考虑混凝土老化的重力坝可靠度分析

为分析混凝土老化导致重力坝可靠度下降问题,考虑大坝及坝基为弹性边界条件,采用模态变换解耦运动方程,再借助于Outaloup滤波器近似,通过传递函数形式将分数阶模式表示为整数阶模式,进而将传递函数转换为含分数阶的振动状态方程;引入虚拟激励法推导出位移响应下的目标方差,采用阻尼抽取法推导出大坝混凝土老化的可靠度及可靠性变化率。实例分析表明,在位移响应目标位移保持不变时,方差越大,可靠度越低;而当位移响应目标方差保持不变时,目标位移越大,可靠度越高。

Reliability Analysis of Gravity Dam Considering Concrete Aging

A fractional order model was utilized to reflect the reliability reduction trend of gravity dams when concrete aging was concerned in motion equations. The solving process of motion equations with a fractional order model was as follows: firstly, considering the elastic boundary condition of dam and dam foundation, the mode transfer was used to uncouple the original equations. Secondly, the integer order modes were determined by aid of Laplace transfer and Outaloup''s filter approximation, and then it was changed into fractional order vibration state equations. Virtual excitation method was used to deduce object variance under response of displacement. The reliability and change ratio of dam concrete aging were derived by the damp extraction method. Instance study shows that when the object displacement of responded displacement remains unchanged, the reliability of dam decreased with increase of variance; while the object variance of responded displacement remains unchanged, the reliability of dam increase with increase of object displacement.