The influence of model assumptions on the dynamic impedance functions of shallow foundations is investigated using finite elements in two studies. The first investigates the effects of model assumptions in different combinations including embedment of the foundation, variation of modulus with depth, and permanent load acting on the foundation. The second study is a parametric analysis investigating the effects of permanent load at varying soil depths and with different soil modulus coefficients. Shallow foundations in strata of frictional soil on top of bedrock are considered. Small-strain modulus and modulus reduction relationships are used in an iterative process to update the modulus due to the permanent load. The results show that model assumptions can have a large influence on impedance functions. The static stiffness coefficients differ, in some instances by more than 100%. The impedance functions, normalized with the static stiffness coefficients match each other well in the pre-resonance frequency range. However, in the frequency range above the fundamental frequency, the normalized impedance functions show a large variation. Further, the results show that the influence of the permanent load is largest in the case of shallow and stiff soil strata, both regarding normalized impedance functions as well as the static stiffness coefficient, which can be increased up to 67%. The change in fundamental frequency was however minimal.

中文翻译：

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模型假设对浅基础动态阻抗函数的影响

在两项研究中使用有限元研究了模型假设对浅基础动态阻抗函数的影响。第一个研究模型假设在不同组合中的影响，包括地基嵌入、模量随深度的变化以及作用在地基上的永久载荷。第二项研究是参数分析，研究永久荷载在不同土壤深度和不同土壤模量系数下的影响。考虑了基岩顶部摩擦土层中的浅基础。在迭代过程中使用小应变模量和模量减少关系来更新由于永久载荷而产生的模量。结果表明，模型假设对阻抗函数有很大的影响。静刚度系数不同，在某些情况下超过 100%。用静态刚度系数归一化的阻抗函数在预共振频率范围内相互匹配良好。然而，在基频以上的频率范围内，归一化阻抗函数表现出很大的变化。此外，结果表明，在浅层和刚性土层的情况下，永久荷载的影响最大，无论是归一化阻抗函数还是静刚度系数，都可以增加到 67%。然而，基频的变化很小。归一化的阻抗函数显示出很大的变化。此外，结果表明，在浅层和刚性土层的情况下，永久荷载的影响最大，无论是归一化阻抗函数还是静刚度系数，都可以增加到 67%。然而，基频的变化很小。归一化的阻抗函数显示出很大的变化。此外，结果表明，在浅层和刚性土层的情况下，永久荷载的影响最大，无论是归一化阻抗函数还是静刚度系数，都可以增加到 67%。然而，基频的变化很小。