考虑频率参数协调的频率相关等效线性化方法

FREQUENCY-DEPENDENT EQUIVALENT LINEAR METHOD FOR SEISMIC SITE RESPONSE CONSIDERING THE COMPATIBILITY OF FREQUENCY PARAMETERS

  • 摘要: 基于土动力试验呈现出的土体动参数频率相关特性,结合一维等效线性化理论,建立了能够考虑动三轴或共振柱测试频率Rf和波速测试频率fvs)相协调的频率相关等效线性化方法。首先,基于国内外不同学者的试验结果,回归建立了土体剪切模量-频率和阻尼比-频率关系式,推导得到了规准化频率相关土体剪切模量比和阻尼比随剪应变变化关系式;其次,对频率无关等效线性化方法进行了改进,传递函数采用频率相关的剪切模量和阻尼比,建立了频率相关的等效线性化方法;最后,采用频率相关和频率无关等效线性化方法,分别对单层覆盖层均质线性场地和单层覆盖层非线性场地进行了不同工况下的土层地震反应分析计算,计算结果表明:1)试验室土动力性能参数测试频率Rf对地震响应影响较大,波速测试频率fvs)影响较小;2)采用动三轴试验给出的土动参数,频率相关方法得到的结果略低于频率无关方法结果。采用共振柱试验给出的土动参数,频率相关方法得到的结果大幅高于频率无关方法结果。

     

    Abstract: Based on frequency-dependent soil behavior demonstrated by laboratory tests and equivalent linearization theory, 1D frequency-dependent equivalent linear method for seismic site response is established, considering the parameter compatibility between the frequency Rf for laboratory dynamic tri-axial test or resonant column test and the frequency f(vs) for shear wave test. Firstly, using the laboratory results given by researchers, the frequency-dependent soil constitute models are proposed through data regression methods, and the formula describing normalized frequency-dependent shear modulus reduction and damp ratio curves with shear strain are deduced. Then, frequency-dependent equivalent linear method is developed by employing frequency-dependent shear modulus and damp ratio in transfer function for the frequency-independent equivalent linear method. Lastly, by using frequency-dependent and frequency-independent methods, linear response for a single-layered site and nonlinear response for another single-layered site under different cases are conducted, and results show that:1) laboratory test frequency Rf has a great impact on site response and shear wave test frequency f(vs) has a minor effect on site response; 2) if the input parameters of shear modulus and damp ratio are obtained by dynamic tri-axial tests, the results obtained by frequency-dependent methods are slightly lower than that obtained by frequency-independent methods; if the parameters are obtained by resonant column tests, the results obtained by frequency-dependent methods are much higher than that obtained by frequency-independent methods.

     

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