地震动卓越周期对在役高墩刚构桥时变响应的影响

为明确地震动卓越周期和材料性能劣化对高墩刚构桥地震响应的影响规律和机理,以某高墩连续刚构桥为背景,采用有限元法分析该桥在不同卓越周期地震波作用下的时变响应;建立与该桥基本周期相对应的单自由度体系,赋予其随服役时间变化的基本周期,分析其在正弦波作用下的时变响应规律及影响机理。结果表明:不同卓越周期地震波作用下,高墩刚构桥墩底截面的内力响应有明显差异,且随服役时间的增加逐渐下降;短、中周期结构的时变地震响应由稳态值主导,而长周期结构的时变地震响应主要受瞬态值控制,材料随服役时间的劣化有助于缓解瞬态值突变带来的不利影响;对于高墩刚构桥(长周期结构),时变响应对地震动卓越周期的变化较敏感。

Effect of Ground Motion Predominant Period on Time-Dependent Response of In-service Rigid Frame Bridge with High Piers

In order to clarify the laws and mechanism of seismic response of rigid frame bridge with high piers affected by ground motion predominant period and material degradation, we adopted the finite element method based on a continuous rigid frame bridge with high piers to analyze its time-dependent responses under ground motions excitation with different predominant periods. Moreover, we established single-degree-of-freedom systems corresponding to the basic periods of the bridge, and gave a basic period along with the variation of in-service time to analyze the time-dependent response laws and influence mechanism under the sine wave excitations. The results show that, under the action of seismic waves with different predominant periods, the internal forces of the pier bottom sections of rigid frame bridge with high piers are obviously different and decrease gradually with in-service time;the time-dependent seismic response of short-and-medium-period structure is dominated by values in the steady state, while the time-dependent seismic response of long-period structure is mainly controlled by the transient value, and the deterioration of materials with in-service time helps to alleviate the adverse effects caused by sudden changes of transient values. For rigid frame bridges with high piers (long-period structures), the time-dependent responses are more sensitive to the change of predominant period of ground motions.