SYNTHETIC METHOD OF FAR-FILED HARMONIC-LIKE GROUND MOTION BASED ON EEMD
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摘要: 远场类谐和地震动是一种特殊的长周期地震动,振动阶段后期产生多个循环的长周期类谐和加速度脉冲,易对长周期结构带来不利影响。然而,由于远场类谐和地震动实测记录有限,能直接用于结构抗震分析的地震动记录更少。为弥补这一缺陷,该文提出一种基于EEMD的远场类谐和地震动人工合成方法并对该方法的合理性和可行性进行验证。该方法通过对远场类谐和地震动记录进行EEMD分解,得到地震动低频成分的类谐和主脉冲成分与衰减部分,并对二者的拟合重构形成类谐和主脉冲分量进行特征参数识别和简化,提出由类谐和脉冲函数和衰减函数相结合的主脉冲速度模型,最后叠加分解时剔除的高频IMF分量形成人工类谐和地震动。基于此,重新选取3条任意远场类谐和地震动记录的地震动特征参数合成人工地震动,与原始地震动反应谱进行对比分析。结果表明:采用EEMD方法可有效提取原始地震动的低频成分,基于所提类谐和主脉冲速度模型得到的主脉冲时程与原始地震动速度主脉冲时程吻合较好;利用所提的地震动合成方法合成的人工地震动可较好保留原始类谐和地震动的非平稳特性,且与原始地震动较为吻合。Abstract: Far-field long-period harmonic-like ground motion characterized with long-period acceleration harmonic-like pulses in the late stage of vibration has adverse effects on the long-period structures. However, there still lacks of far-field ground motion records that could be directly used for seismic analysis due to limited records of ground motions. A synthetic method for far-filed harmonic-like ground motion based on Ensemble Empirical Mode Decomposition Method (EEMD) was proposed to solve the problem of shortage of available far-field ground motions, and its accuracy and feasibility was verified. The recorded far-field long-period harmonic-like ground motions were decomposed through EEMD to obtain the main-pulse composition and attenuation of low-frequency component, which were fitted and reconstructed to generate harmonic-like main-pulse component. Then the identification and simplification of characteristic parameters for the synthetic harmonic-like main-pulse components were conducted to obtain the main-pulse velocity model, which composed of harmonic-like main-pulse function with attenuation function. The synthetic method for far-filed harmonic-like ground motion was proposed based on combination of the main-pulse velocity model and high-frequency IMF components. In addition, the synthesis of three arbitrary harmonic-like ground motions according to selected characteristics parameters was carried out, and the comparisons with the original far-field long-period harmonic-like ground motions was conducted. The results demonstrated that the low-frequency component of original ground motion could be effectively extracted with EEMD and the velocity-time history obtained from the proposed main-pulse velocity model fitted well with the velocity-time history of the original ground motion. The proposed synthetic method could generate artificial harmonic-like ground motion that retained the non-stationary characteristics of the far-field harmonic-like ground motion, and fit well with the original ground motion.
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表 1 选用远场类谐和地震动信息
Table 1. Parameters for far-filed harmonic ground motions
台站 震级 震中距/
km加速度峰值
(PGA)/g速度峰值
(PGV)/(m·s−1)位移峰值
(PGD)/m持时
Tp/sILA004-N 7.62 88.89 0.064 0.026 0.020 5.255 ILA004-W 7.62 88.89 0.073 0.030 0.024 5.128 ILA005-N 7.62 84.88 0.080 0.016 0.012 4.823 ILA005-V 7.62 84.88 0.026 0.011 0.010 9.680 ILA041-N 7.62 85.66 0.063 0.022 0.018 4.920 ILA048-N 7.62 92.04 0.077 0.025 0.019 4.390 ILA055-N 7.62 88.05 0.069 0.024 0.021 5.450 ILA055-W 7.62 88.05 0.076 0.030 0.026 5.045 ILA056-N 7.62 92.04 0.066 0.032 0.025 5.010 ILA056-W 7.62 92.04 0.071 0.033 0.032 5.410 TCU008-E 7.62 84.95 0.068 0.029 0.038 7.640 TCU083-E 7.62 80.18 0.091 0.031 0.043 7.460 CHY032N 6.20 50.17 0.041 0.014 0.012 5.560 CHY032E 6.20 50.17 0.033 0.007 0.005 4.240 CAL-UP 7.20 54.77 0.041 0.007 0.005 4.334 表 2 远场类谐和地震动速度时程简化参数表
Table 2. Parameter metric for the simplification of far-field harmonic ground motions velocity time history
地震波名称 成分 简谐段 衰减段 初始幅值/(m·s−1) 周期Ts/s 持时Tp/s 初始幅值VA2/(m·s−1) 周期Ta/s 持时Td/s 衰减指数λ ILA004-N 低频 0.2200 5.255 21.02 0.140 3.8 53.78 1/12 ILA004-W 低频 0.2400 5.128 25.64 0.110 6.0 54.28 1/15 ILA005-N 主脉冲 0.1100 4.823 16.88 0.050 6.1 104.36 1/35 ILA005-V 主脉冲 0.0700 9.680 9.68 0.040 4.8 121.20 1/35 ILA041-N 低频 0.1900 4.920 12.30 0.120 4.0 49.60 1/25 ILA055-N 低频 0.2000 5.450 16.34 0.140 5.0 124.06 1/25 ILA055-W 低频 0.2300 5.045 20.18 0.100 5.1 122.06 1/35 ILA056-N 低频 0.2500 5.010 20.04 0.110 3.0 67.26 1/20 TCU083-E 主脉冲 0.2000 7.460 7.46 0.140 4.6 27.32 1/35 CHY032E 主脉冲 0.0475 4.240 6.36 0.035 4.5 19.48 1/10 CHY032N 主脉冲 0.0758 5.560 11.12 0.035 3.5 18.88 1/15 CAL-UP 主脉冲 0.0550 4.334 6.50 0.028 4.0 156.12 1/80 表 3 所选远场类谐和地震动速度特征参数
Table 3. Characteristic parameter of velocity for selected ground motion
地震动 简谐段 衰减段 初始幅值VA1 周期Ts 持时Tp 初始幅值VA2 周期Ta 持时Td 衰减指数λ ILA048-N 0.20 4.39 8.78 0.12 3.8 72.52 1/25 ILA056-W 0.24 5.41 24.34 0.12 4.5 71.14 1/20 TCU008-E 0.19 7.64 7.64 0.18 4.5 22.50 1/12 -
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