Rayleigh波作用下单桩的横向非线性动力响应研究

发布时间：2018-07-04 09:38

本文选题：远场地震 + 环境振动　；参考：《上海理工大学》2014年硕士论文

【摘要】：地震工程科学在分析地震激励下土-结构相互作用包括两个不同的方面:第一,确定场地的自由场反应;第二,计算在地震环境下自由场上建有结构后地震动的改变和实际相互作用。远场地震和环境振动所引发的地层振动,主要是由Rayleigh波引起的。作为一种重要的结构形式,桩基础因其卓越的优点被广泛应用于软土地基中。因此,定量计算Rayleigh波作用下桩基的横向动力响应,对桩基的工程设计具有重要的意义。当前,关于Rayleigh波作用下桩基础的横向动力响应问题,大多是在均质半空间、线粘弹性和频域内完成的,这并不能满意地描述Rayleigh波作用下桩基础的动力学响应。本文主要在层状地基、迟滞非线性和时域内研究Rayleigh波作用下桩基础的横向动力响应。首先,需要确定Rayleigh波作用下层状地基的自由场反应。本文通过引入势函数和有限元思想,推导了Rayleigh波在层状地基中的特征方程,分别建立了解析法和有限元-解析法,这两种方法各有其鲜明的优缺点。根据特征方程的数值计算特点,在频率-波数域(f-k域)内应用BISECTION算法,快速、准确地搜索Rayleigh波特征方程的根。进而得到了各种常见地基中Rayleigh波高阶模态的频散曲线,计算结果得到了现场实测的频散曲线的支持。在此基础上,深入研究了层状地基中Rayleigh波频散特性及随深度的位移衰减特性。其次,选用BWGG模型来模拟桩侧土体的迟滞非线性。通过拟合既有的试验模型和对BWGG模型的每个参数的灵敏度分析,确定了每个参数有效的取值范围。再利用室内动三轴循环加载试验对BWGG模型进行修正,修正后的模型更加简洁,且能够反映循环次数N对土体刚度和强度弱化的影响。接着,基于动力Winkler地基梁模型和BWGG模型建立了一个新的、能够考虑各种非线性因素影响的、研究单桩横向非线性动力响应的简化分析模型。采用Galerkin法对模型的动力方程进行离散,利用Newmark-β法实现对桩-土相互作用系统的时域数值解和动力非线性响应分析,并于试验解进行了比较,验证了本文方法的正确性和有效性。最后,将Rayleigh波作用下自由场地的动力反应作为边界输入施加到桩-土相互作用模型中,研究了单桩在Rayleigh波作用下的横向非线性动力特性。作为工程应用,计算了上海光源工程中单桩在Rayleigh波作用下的横向非线性动力响应。
[Abstract]:The analysis of soil-structure interaction under earthquake excitation in seismic engineering science includes two different aspects: first, determining the free field response of the site; second, The change of ground motion and the actual interaction after the structure of the free field are calculated in earthquake environment. The formation vibration caused by far field earthquake and ambient vibration is mainly caused by Rayleigh wave. As an important structural form, pile foundation is widely used in soft soil foundation because of its outstanding advantages. Therefore, the quantitative calculation of the lateral dynamic response of pile foundation under Rayleigh wave is of great significance to the engineering design of pile foundation. At present, the transverse dynamic response of pile foundation under Rayleigh wave is mostly completed in homogeneous half-space, linear viscoelasticity and frequency domain, which can not satisfactorily describe the dynamic response of pile foundation under Rayleigh wave. In this paper, the transverse dynamic response of pile foundation under Rayleigh wave is studied in layered foundation, hysteretic nonlinear and time-domain. First, it is necessary to determine the free field response of layered foundation under Rayleigh waves. In this paper, the characteristic equations of Rayleigh wave in layered soil are derived by introducing the potential function and finite element method. The analytical method and the finite element analytical method are established respectively. The two methods have distinct advantages and disadvantages. According to the numerical calculation characteristics of the characteristic equation, the BISECTION algorithm is used in the frequency-wavenumber domain (f-k domain) to search the roots of the Rayleigh wave characteristic equation quickly and accurately. The dispersion curves of high order modes of Rayleigh waves in various kinds of foundations are obtained, and the calculated results are supported by the measured dispersion curves in the field. On this basis, the dispersion characteristics of Rayleigh waves and the attenuation characteristics of Rayleigh waves with depth in layered soil are studied. Secondly, BWGG model is used to simulate the hysteresis nonlinearity of soil around the pile. By fitting the existing experimental model and analyzing the sensitivity of each parameter of the BWGG model, the effective value range of each parameter is determined. The BWGG model is modified by indoor dynamic triaxial cyclic loading test. The modified model is more concise and can reflect the influence of cyclic times N on soil stiffness and strength weakening. Then, based on the dynamic Winkler foundation beam model and the BWGG model, a new simplified analysis model for the lateral nonlinear dynamic response of a single pile is established, which can take into account the influence of various nonlinear factors. The Galerkin method is used to discretize the dynamic equations of the model, and the Newmark- 尾 method is used to analyze the time-domain numerical solution and the dynamic nonlinear response of pile-soil interaction system. The numerical results are compared with the experimental results, and the correctness and validity of the proposed method are verified. Finally, the dynamic response of the free site under Rayleigh wave is applied as the boundary input to the pile-soil interaction model, and the transverse nonlinear dynamic characteristics of a single pile under Rayleigh wave are studied. As an engineering application, the transverse nonlinear dynamic response of a single pile under Rayleigh wave in Shanghai Light Source Project is calculated.
【学位授予单位】：上海理工大学
【学位级别】：硕士
【学位授予年份】：2014
【分类号】：TU435;TU473.1

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