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针对已有场地基本周期简化公式不适用含软夹层场地的问题,从振动的角度推导出能反映土层结构影响的场地基本周期估算公式。根据自振周期相等的原则,推导出单层土场地简化为单自由度体系的等效高度系数;以水平成层场地中任一土层厚度与这一系数之积作为体系高度,将场地简化为相应的单自由度体系,定义体系的自振周期为该土层的贡献基本周期,场地中所有土层贡献基本周期的平方和开平方即为场地的基本周期,并推导出相应的计算公式。检验结果表明,所推导公式不仅能够合理地反映土层结构对场地基本周期的影响,而且对实际工程场地基本周期的估算结果亦较已有公式的结果更接近地脉动测试结果。公式可用于估算水平成层场地的基本周期。
Aiming at the problem that the simplification formula of the basic period of the existing site is not suitable for the site with soft mezzanine, the formula of estimating the basic period of the site that can reflect the influence of soil structure is derived from the perspective of vibration. According to the principle of equal period of natural vibration, the equivalent height coefficient of single-layered soil system simplified to single-degree-of-freedom system is deduced. Taking the product of the thickness of any soil layer in horizontal layered structure and this coefficient as the system height, For the corresponding single-degree-of-freedom system, the natural period of the system is defined as the basic contribution period of the soil layer. The square root of the basic periodicity of contribution to all soil layers in the site is the basic period of the field, and the corresponding formula . The test results show that the derived formulas not only can reasonably reflect the influence of soil structure on the basic period of the site, but also estimate the basic period of the actual project more closely than the results of the existing formulas. The formula can be used to estimate the basic period of horizontal stratigraphic sites.