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寻求合理高效的方法求得不同材料阻尼特性混合结构的地震作用及其效应是工程抗震界较为关注的问题之一。目前,用于计算不同材料阻尼特性混合结构地震作用效应的复模态叠加法和直接积分法都是基于黏性阻尼假定推导而来。黏性阻尼假定存在能量耗散与激振频率有关的缺陷,导致结构高频模态地震作用效应偏小,且阻尼矩阵与复模态分析结果相互影响,计算结果不唯一,合理性不易被判定。复阻尼假定避免了黏性阻尼假定的不足,但通常求得的地震作用效应为复数,不便于工程应用。为此提出一种基于复阻尼假定的复模态叠加法,直接在物理空间中求解,计算结果唯一,比基于黏性阻尼假定的复模态叠加法计算效率更高。与运用本文方法计算的地震作用效应结果相比,广为采用的折算阻尼比方法计算结果是不合理的。此外,给出了基于复阻尼假定的计算模态有效质量系数的方法,可用于确定合理的叠加模态个数。
Seeking a reasonable and efficient method to obtain the seismic effect and its effect of the hybrid structure with different damping characteristics is one of the more concerned problems in the seismic engineering of engineering. At present, the complex modal superposition method and the direct integral method, which are used to calculate the seismic effect of mixed structures with different damping characteristics, are derived based on viscous damping assumption. Viscous damping assumes the existence of energy dissipation and excitation frequency related defects, resulting in structural high-frequency modal seismic effect is small, and the damping matrix and the complex modal analysis results affect each other, the calculation results are not unique, the rationality is not easy to be judged. Complex damping is assumed to avoid the assumption of viscous damping, but the seismic effect usually obtained is complex, which is not convenient for engineering applications. For this reason, a complex modal superposition method based on complex damping assumption is proposed, which is directly solved in physical space. The calculation result is unique, which is more efficient than the complex modal superposition method based on viscous damping assumption. Compared with the result of seismic action calculated by this method, it is unreasonable to use the widely used method to calculate the damping ratio. In addition, a method to calculate modal effective mass coefficient based on complex damping assumption is given, which can be used to determine the reasonable number of superposition modes.