绝对位移直接求解虚拟激励法采用附加振型求解的理论研究

为提高已有绝对位移直接求解虚拟激励法的求解效率及精度，对结构支座节点附加大质量块并释放支座约束，采用基于附加振型的振型分解法进行求解，附加振型来源于附加大质量块。对附加振型、常规振型的振型特性和振型贡献及计算效率进行了理论分析，分析表明：通过构建少量附加振型就可精确捕获结构拟静位移，且只需采用与相对运动法同等数量的常规振型就可精确捕获结构动态相对位移，与Wilson位移输入模式的绝对位移振型分解法相比，在保证计算精度的条件下可大大减少绝对位移求解所需的振型数。此外，对附加振型绝对位移求解法阻尼误差进行了理论分析，指出了附加振型法不存在由于阻尼假定不同而引起的误差，计算精度及效率均优于基于完全法的绝对位移直接求解法。

Analysis of absolute displacement direct solving pseudo excitation method based on additional mode decomposition

 The structures were solved by mode decomposition with additional mode by adding big mass in support nodes, in order to improve the calculation accuracy and efficiency of last pseudo excitation method based on solving absolute displacement. The additional modes are caused by adding big mass. The contribution and characterizes of additional and normal modes and calculation efficiency of new algorithm were analyzed. It is shown that only few additional modes can capture pseudo-static displacement response accurately, and adopting same numbers normal modes with relative motion method can capture same accurate dynamic relative displacement response. Compared with displacement input model presented by Wilson, the method can result in a significant savings in combination mode numbers in the same accuracy. The calculation errors caused by damping assuming difference don’t exist in the new algorithm, which is superior to old pseudo excitation method based on solving absolute displacement in accuracy and efficiency.