基于剪应力时程极值的损伤值等效转换及其在土石坝多点输入地震反应中的应用

Equivalent damage value transform according to extrema of shear stress time history and its application in earth and rockfill dam's response to multi-point earthquake input

等效地把动剪应力转化为损伤值有两种方法,一是根据其峰值,二是根据其极值。后一种方法克服了前一种方法的不足,它根据极值序列是否穿零将其分组,把组内的最大值以及组内应力对两极值之差分别转换为损伤值。以人工合成的、进行了速度归零化处理的40个外部节点的水平和竖向地震加速度时程作为输入,考察大坝的损伤值反应,结果表明,第一种方法算出的损伤值会依赖于两个条件:延时分析时间段的长短和计算采用的时间步长的大小,而基于极值的损伤值计算不依赖于这两个条件,说明了第二种方法的优越性。第一种方法比第二种方法算出的大坝的破坏区域大,第一种方法较为保守。

Dynamic Shear Stress can be transformed equivalently to damage value in two methods, the first is according to its peak value, and the second is according to its extrema. The second method overcomes the first's shortage, and it classes the extrema into stress groups according to whether the extremum sequence run across the zero line. The max and the margin between two extrema of the stress couples in every extremum group are individually transformed to damage value. With the input of horizontal and vertical artificial acceleration history of 40 outer points whose velocity is zeroized, the damage value response is analyzed. The computation case shows the first method depends on two factor, one of which is how long of the delay time for dynamic analysis, and another is how long of the given time step; while the second method is independent on those two factors, which proves the superiority of the second method. The damaged area in dam's slope computed by the first method is bigger than the damaged area computed by the second method, which means the first method is conservative.