基于HHT变换瞬时能量谱的长周期结构地震反应分析

基于HHT变换得到瞬时能量谱,并以简谐地震反应为理论基础进行多自由度体系在地震动作用下的瞬态反应计算。通过对一个长周期(十五层)结构工程实例的地震瞬态反应计算分析,揭示长周期结构有别于短周期结构动力响应的独特特性:长周期结构位移响应的瞬时能量峰值的时间滞后于地震动能量峰值的时间,且主要受到瞬态振动的控制,并以低阶振型的控制为主,第一阶振型峰值位移滞后的时间最长,滞后的时间主要取决于结构的第一阶自振周期。研究结果表明,长周期结构在强烈地震动作用下,地震动强度出现的最大时刻并不总是对应于结构破环与倒塌的时间。

Seismic Response of Long-period Structures Based on the Instantaneous Energy Spectrum Obtained by the Hilbert-Huang Transform

To reveal the failure mechanism of long-period structures, we obtained the instant energy spectrum by the Hilbert-Huang transform (HHT), and analyzed the structure''s displacement response based on the theory of simple harmonic seismic response. The transient response of a MDOF system was also calculated based on a harmonic earthquake response analysis. Notable characteristics on long-period structures were different from short-period structures, based on analyses of the transient vibration patterns of a long-period (e.g., 15 layer) building. First, the time of peak displacement response on the structure was always observed to be later than the time of peak value of earthquake energy. Second, the displacement response was mainly controlled by the transient response in low order modals. Third, the first order modal displacement hysteresis lasted the longest, and the hysteresis mainly depended on the natural vibration period of the structure. The conclusions showed that demolition and collapse of long-period structures due to the strong earthquake did not happen at the greatest density of earthquake ground motion.