When performing seismic site response analyses in the design practice, one of the main issues consists in finding a compromise between the limited availability of site-specific experimental data to characterise the cyclic soil behaviour and the necessity of a proper constitutive representation of such behaviour, including nonlinearity, hysteresis and strength. This paper presents a new constitutive approach for 1D nonlinear soil models, capable of describing such features with a simple and easy to calibrate constitutive equation, requiring the definition of few parameters, all derived from conventional field and laboratory data. The main element of novelty in the proposed approach consists in recognizing that the soil shear strength is a key ingredient not only to limit the maximum shear stress that the soil can experience at large strains, but also to describe the dependence of the nonlinear soil properties on mean effective stress and plasticity index, as observed in the medium strain range. Based on a thorough comparison with laboratory data, it is shown that the proposed model provides a very good description of the soil behaviour, in the whole strain range. Its application in site response analyses is further validated on centrifuge data and verified against other nonlinear constitutive soil models. Finally, using a well-characterised site in Italy as reference, it is demonstrated that an erroneous prediction of the soil shear strength can lead to a misinterpretation of the amplification phenomena within the soil deposit, together with a possible gross underestimation of the actual surface acceleration.

中文翻译：

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一维站点响应分析中的非线性和强度：一种简单的本构方法

在设计实践中进行地震现场响应分析时，主要问题之一在于在有限的可用于表征周期性土壤行为的现场特定实验数据的可用性与适当地本构表示这种行为的必要性之间找到折衷方案，包括非线性，磁滞和强度。本文提出了一种用于一维非线性土壤模型的新的本构方法，该方法能够通过简单且易于校准的本构方程来描述此类特征，需要定义很少的参数，所有这些参数均来自常规现场和实验室数据。提出的方法的新颖性主要在于认识到土壤的抗剪强度是关键因素，不仅限制了土壤在大应变下可以承受的最大剪切应力，而且还描述了在中等应变范围内观察到的非线性土壤特性对平均有效应力和可塑性指数的依赖性。通过与实验室数据的全面比较，表明所提出的模型可以很好地描述整个应变范围内的土壤特性。它在现场响应分析中的应用在离心机数据上得到了进一步验证，并针对其他非线性本构土壤模型进行了验证。最后，使用意大利一个特征鲜明的地点作为参考，这表明对土壤抗剪强度的错误预测可能导致对土壤沉积物内放大现象的误解，并可能严重低估了实际表面加速度。