دانلود رایگان مقاله انگلیسی روش مدل سازی عددی برای رفتار غیر ارتجاعی و وابسته به فرکانس پی های سطحی - الزویر 2017

ABSTRACT

This paper presents a novel framework with which the inelastic behavior and the frequency-dependent dynamic characteristics of soil-foundation system can be represented with a computationally efficient numerical model. The inelastic behavior of soil in the vicinity of a shallow foundation is represented with a macro-element which is based on the classical plasticity theory. The frequency-dependent property of soil-foundation system is represented with a recursive parameter model. The framework allows integration of both models such that both the inelastic behavior and the frequency-dependent characteristics can be captured. The proposed method is verified against FE analysis of a shallow foundation in the two dimensional parametric space of frequency and inelasticity. The verification shows that the model using the proposed framework can fully represent the inelastic cyclic behavior at low frequency excitation and the dynamic response at high frequency excitation. The method provides an approximate solution for the cases in-between, e.g. a foundation subjected large amplitude high-frequency excitation. As an application example, the method is applied to an analysis of a bridge pier subjected to earthquake loading.

5. Conclusion

The paper presents a new framework to integrate the nonlinear model of soil foundation system with frequency dependent properties of soil in dynamic loading application. The nonlinearity of the soil and foundation system is captured with a computationally efficient macro element by Chatzigogos [17] while the frequency dependent behavior of soil-foundation system is captured with a recursive parameter model in Nakamura [20,21]. The proposed framework, however, is very general such that any other nonlinear element or frequency-dependent model can be integrated.

The results from the proposed framework have shown good agreement with FE model at low amplitude excitation with a broad range of frequencies. Also, the model can capture the nonlinear behavior of soil foundation system with uplift of the foundation at high amplitude excitation with low frequency. However, the accuracy of the model decreases when both the excitation frequency and magnitude are high. Thus, there exist still limitation in capturing a full inelastic frequency dependent behavior of soil foundation system. This limitation might be one of the shortcomings of the proposed framework in application to structures with significant higher mode effects.

It is also worthwhile to mention that while the framework was implemented for shallow foundations, the framework can be applied to embedded or deep foundations as long as reliable inelastic model and dynamic impedance functions are available. In addition, depending on the characteristics of the analyzed structure, the impact of the nonlinearity or frequency-dependency of soil-foundation system is expected to be different. Thus, it is equally important to have good understanding on structural characteristics when determining the modelling approach for soil-foundation system.