基于谱分析与RC梁桥检验的脉冲型近场地震动强度度量指标

近场地震动和远离震源地区的地震地面运动存在显著区别,速度脉冲是其造成巨大震害后果的主要因素之一,有必要深入研究近场速度脉冲破坏能力的合理度量指标。在既有脉冲模拟模型的基础上,引入一种采用三角函数叠加不同比例高频分量的速度脉冲模拟模型,考虑地震下结构的累积能量和瞬时能量需求,以强度和能量为指标,对近断层地震的速度脉冲效应进行单自由度(SDOF)体系的谱分析,对不同脉冲参数下结构地震响应的影响程度进行定量对比。结果表明:同类脉冲下,累积输入能量受高频地震分量影响明显,而瞬时输入能量则主要取决于速度脉冲的自有强度,脉冲持时与结构自振周期之比、脉冲峰值是决定结构地震响应的最主要因素,从而构建表征速度脉冲强度的度量指标,并采用14条包含典型脉冲的近场地震记录为输入,以一座五跨连续梁桥为算例验证该指标的合理性。

Intensity Indice of Impulsive Near-fault Earthquake Ground Motion Based on Spectra Analysis and RC Bridge Check

There are apparent differences between near-fault earthquake ground motions and ground motions far from the earthquake focus,and velocity pulses are one of the primary factors causing huge earthquake damages.So it is necessary to seek for reasonable intensity indice of the destructive capability of near-fault velocity pulses.The trigonometric function superimposed with high-frequency components of different proportions was introduced into the existing pulse simulation models.Taking into account the cumulative energy amount and instantaneous energy demand of structures in earthquake,setting the strength and energy amount as the indice,spectra analysis of the SDOF system was carried out to analyze the velocity pulse effect of the near-fault earthquake.The influence of different pulse parameters on earthquake responses of structures was compared quantitatively.The research results show as follows: Under the action of the same kind of pulses,cumulative input energy is affected significantly by high-frequency components,and instantaneous input energy depends mainly on the inherent intensity of velocity pulses;the peak value of the velocity pulse and the ratio of pulse duration to the self-vibration period of structures are the two most important factors to determine the earthquake responses of structures;the intensity indice is extracted as the index to characterize the strength of velocity pulses,and its rationality is verified by example of a five-span continuous bridge under the excitation of near-field earthquake recorded in 14 notes containing typical velocity pulses.