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平面波输入下海水-海床-结构动力相互作用分析

ANALYSIS OF WATER-SEABED-STRUCTURE DYNAMIC INTERACTION EXCITED BY PLANE WAVES

  • 摘要: 海洋工程结构的地震反应分析是保证海洋工程结构地震安全的重要环节.由于其所处的复杂环境, 该问题涉及到流固耦合和土-结相互作用.本文基于海水、饱和海床、基岩流固耦合统一计算框架,采用Davidenkov模型和修正的Masing准则考虑饱和海床的非线性,在脉冲SV波垂直入射下, 进行了海域场地和海洋工程结构的动力响应分析. 首先,对比分析了线性自由场和非线性自由场输入情形的海域场地非线性反应,结果表明线性自由场输入时反应不合理,自由场分析和场地分析应该采用相一致的本构模型. 然后,对比分析了海床分别为线性和非线性情形时,海域场地以及海水-海床-结构体系的反应特征. 与线性海床情形相比,非线性对海床反应的影响主要由如下两方面因素控制: 一方面,非线性导致饱和海床模量减小, 饱和海床与基岩间的波阻抗比减小,由基岩到饱和海床间的反射系数和透射系数增加, 导致反应增大; 另一方面,非线性导致阻尼加大, 使海床反应减小. 对于本文算例而言,阻尼对非线性海床结果的影响占主导作用.

     

    Abstract: The seismic response analysis of marine engineering structures is important to ensure the seismic safety of these structures. Marine engineering structures are always built in a complex environment where there are both water and soil. So both fluid-structure interaction and soil-structure interaction need to be considered in seismic response analysis of marine engineering structures. This paper is based on the unified calculation framework for wave motion in water-saturated seabed-bedrock system, and uses the Davidenkov model and modified Masing rule to describe the nonlinear characteristics of saturated seabed. The dynamic responses of marine sites and marine engineering structures when the pulse SV wave incident vertically are analyzed. First, the nonlinear responses of marine sites under the input of linear free field and nonlinear free field are analyzed comparatively. The results show that the nonlinear response of the marine site under the input of the linear free field is unreasonable. So it means the consistent constitutive model should be used for the free field analysis and finite element analysis of marine site. Then, the characteristics of responses of the marine site and water-saturated seabed-bedrock system when the seabed is linear or nonlinear are analyzed comparatively. Compared with the case that the seabed is linear, the influence of nonlinearity on response of seabed is mainly controlled by the following two factors: on the one hand, the modulus of saturated seabed decreases because of nonlinearity, so the wave impedance ratio between saturated seabed and bedrock decreases, and then, the reflection coefficient and transmission coefficient from bedrock to saturated seabed increase, resulting in the increase of response; on the other hand, the nonlinearity of saturated seabed causes the increase of damping, resulting in the decrease of response. For the example in this paper, the effect of damping dominate the result when seabed is nonlinear.

     

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