基于反应谱法的某高拱坝动力分析有效振型阶数探讨

多振型反应谱动力分析时,所取振型阶数会影响计算结果的精度和可靠性,而合理的阶数与结构的复杂性有关。以某高拱坝为例,计算了横河向、顺河向、竖直向三个方向地震单独激励下各阶振型参与质量系数及其累计值、对应的位移和应力,以此确定合理的振型阶数。结果表明,各阶振型参与质量系数的大小变化并无明显规律,但当振型阶数达6～7时其累计值将超过90%,此时坝体最大的位移及最大主应力均趋于稳定,其后振型对地震作用效应影响已不超过5%;与横河向和顺河向地震激励相比,需取较多的振型阶数才能得到较为稳定的位移和应力。

Discussion on Effective Modal Order in Dynamic Analysis of High Arch Dam Based on Response Spectrum Method

In dynamic analysis of multimode response spectrum, the order of the vibration mode will affect the accuracy and reliability of the calculation results, while the reasonable order is related to the complexity of the structure. Taking a certain high arch dam as an example, we calculate modal participating mass ratio of each mode of vibration, the cumulative values and the corresponding displacement and stress in longitudinal river, transverse river and vertical direction of the three earthquakes alone. The results indicate that there is no obvious change in modal participating mass ratio of each mode of vibration. But when the number of mode of vibration reaches 6-7, the cumulative value will exceed 90%, and the maximum displacement and maximum principal stress of the dam tend to be stable and the effect of the subsequent mode on the seismic effect has not exceeded 5%. Compared with the transverse and longitudinal river direction, more vibration modes are required to obtain more stable displacement and stress.