the precious method to simulate earthquake accelerations is not perfect because the points on the interface still move according to the simulated acceleration when the points " motion ends, which is obviously a paradox . if the points " velocity is not zeroized, soil's damage value based on shear stress's peaks or extrema is overestimated in multi-point input analysis . the new method's rationality is analyzed 以往人工合成的地震波在地震结束时即地震加速度恒为零时速度不为零,这与合成地震动是“模拟输入点从静止到运动再到静止的运动过程”这一要求不一致,同时导致时域内多点输入分析时差动力过大以至算出的损伤值过大,于是本文提出了简易的地震动速度归零化方法并分析了其合理性。
if the inputted accelerations are velocity-zeroized and the damage value is calculated according to shear stress " extrema, as to 100-meter-high earth dam, multi-point effect is not distinct; but as to 240-meter-high earth dam, in the part where permanent displacement and damage value is originally bigger the response is less tenser than that by one-point input, and in the part near basement the maximal shear stress and damage value is bigger, that is the multi-point effect in time domain 若同时进行了多点地震动速度归零化和采用基于极值的损伤值计算方法,对于100米高的土石坝,多点输入与单点输入反应十分接近。对于240米高的超大型土石坝,坝体内永久位移和损伤值较大的部位多点输入的反应量较小,这是多点输入反应的特点或说多点效应。另外,多点效应也包括坝基部位的最大动剪应力和损伤值偏大这一效应。