脉冲型地震动模拟与隔震桥墩性能的能量分析

Simulation of Pulse-Type Earthquake Excitation and Energy Performance of Isolated Bridge Piers

用改进的三角函数方法来模拟近断层地震地面激励,对非线性隔震桥梁单墩模型进行了地震响应和能量分析.通过对波形、脉冲周期和峰值速度等地震动参数的调整来表征不同的脉冲效应,在前向、前后向和多环3种不同的脉冲波作用下,隔震桥墩反应规律类似,以第3种冲击形式结构的响应值最大、输入结构的地震动能量最多.脉冲周期是决定地震动破坏能力的重要参数,通过定义累积滞回耗能比和瞬时耗散能量比,表明隔震支座有效耗能能力在短周期脉冲作用下较小,在长周期部分趋于稳定,而在中短周期部分单纯依靠隔震支座耗能不足以有效降低地震危害.通过引入瞬时输入能量概念,表明瞬时地震输入能量和结构地震响应密切相关,用瞬时输入能量来表征地震动强度是合适的指标.

Three kinds of near-fault earthquake ground motions are simulated to discuss the earthquake response of isolated bridge piers with bi-linear isolation bearings. By modifying the pulse parameters of simulated earthquakes, it is clear that pulse period is a key factor to effect structure seismic response. When the structure period is close to that of pulse earthquake, great damage would occur. Via the concept of gross energy consuming and momentary energy consuming, a certain extent increase of gross and momentary energy consuming proportion takes place when the pulse period is close to structure period, however the structure response is still severe, so the use of isolated bearing by oneself is not enough to withstand high peak value near-fault earthquakes. The transient input energy is found to be a parameter for the momentary intensity of input energy, which is related to the characteristics of earthquakes and to the response displacement of structures immediately. It is an effective strategy to adopt such parameter to denote the momentary earthquake intensity.