【作者】 岳庆霞；

【导师】 李杰；

【作者基本信息】 同济大学 ， 结构工程， 2007， 博士

【摘要】 地下综合管廊是将两种或两种以上的管线放置其中而形成的一种公共基础设施。它是城市生命线工程基础设施发展的方向,与此同时,对其进行地震作用下的响应及抗震可靠度研究具有重要的理论和现实意义,但这方面却基本未见文献提及,基于这种背景,提出了本文的研究课题。本文首先对影响地下综合管廊结构地震响应分析正确性的关键因素(如人工边界条件、有效应力法等)进行了研究,并用算例进行了说明,这些研究为地下综合管廊的地震响应分析奠定了基础。然后借助有限元软件ABAQUS,建立了三维有限元整体分析模型。在有限元模型中,考虑了人工边界条件、接触面、土体塑性以及土体有效应力等要素。对地下结构的地震动输入形式进行了研究,指出用位移输入可以得到更精确的结果。在以上研究的基础上,对地下综合管廊在地震作用下的响应进行了分析,并对主要影响因素,如人工边界条件、接触面、有效应力、行波效应以及非一致地震激励分别进行了分析比较。研究发现,地下综合管廊在剪切波作用下呈现整体弯曲变形,与土体在剪切波作用下的变形相同。边界条件及非一致激励对结构响应的影响最大,其中自由边界与无限单元的情况,相对误差最大可达153.03%,最小也达到了66%。而非一致激励比一致激励应变幅值有很大增加,最小达到了30%,最大则达到了8倍。因此,在地下综合管廊结构分析中应对边界条件及多点地震动输入特别注意。地下综合管廊属于浅层地下结构,埋深较浅,面波尤其是Rayleigh波将对其响应影响巨大。本文研究了土体中Rayleigh波的传播特性,根据Rayleigh波的特点,首次提出了近似Rayleigh地震波场的概念,并利用傅立叶变换求得近似Rayleigh地震波场,研究了地下综合管廊结构在Rayleigh波作用下的响应。研究表明:对于浅埋地下结构而言,Rayleigh波的影响不可忽略,且呈现出与剪切波作用不同的特点,结构顶面对应点的轴向应变幅值是对应底面点的2倍左右。借助本课题组进行的振动台试验,将数值结算结果与试验结果进行了对比,结果表明,二者符合较好。这一方面验证了本文计算建模方法的正确性,也为后续的研究奠定了基础。结构设计的最终目的,是试图实现基于可靠度的设计。本文将基于物理随机地震动模型进行了扩展,与谱表现方法相结合,合成了多点随机地震动。利用概率密度演化方法,计算了地下综合管廊结构在随机地震动作用下的随机地震反应。并分析了地下综合管廊结构的破坏机制,利用等价极值事件思想,计算了地下综合管廊结构的抗震可靠度,为实现地下综合管廊动力可靠性的精细化分析奠定了基础。更多还原

【Abstract】 A utility tunnel is a public underground structure that holds wires, conduits, and pipes of power, gas, water supply and communication utility system and provides also enough space for maintance opertation. Contruction of utility tunnel represents the future orientation of development for underground infrastructure system in both megalopolis and small towns due to its many advantages as improving the reliability, reducing deferred maintenance and improving the environment. However, few researches have been carried out so far about the dynamic responses and reliability of utility tunnel under earthquake attack. This fact invokes the research of this paper.This paper first investigates some key factors that are crucial for proper earthquake response analysis of utility tunnel, such as artificial boundary conditions and the effective stress method. And some examples are investigated. This has laid a solid foundation for modeling of utility tunnel. Taking ABAQUS as a platform, a three dimentional finite-element-model (FEM) of soil-structure system is estabilished, in which the artificial boundary conditions, contact between soil and structure, the plasticity of soil and the effective soil stress method are considered. The type of input for underground structure analysis is then studied and it is found more accurate responses can be obtained when displacement time history of earthquake wave is adopted. Based on all the above results, the dynamic seismic response of utility tunnel has been calculated using the proposed model. The influences of factors as artificial boundary conditions, contact feature, effective stress method, wave passage effect and inconsistent seismic excition on the dynamic responses of unitily tunnel has been investigated. The results reveal that the utility tunnel show global bending deformation pattern under shear wave excitation and the amplitude of deformation is the same as soil. The artificial boundary conditions and the inconsistent excitation have much more significant influence on the structural responses than other factors. Therefore, special attention should be paid on these two factors for seismic responses analysis. Since the utility tunnel is a typical shallow-buried structure, the earthquake surface wave especially Rayleigh wave will have considerable effect on the structural response. To learn the effect of Rayleigh wave, the propagation characteristics of Rayleigh wave in soil is reviewed and approximate Rayleigh earthquake wave is simulated using Fourier transform technique. Taking the simulated Rayleigh wave as input, the seismic response of utility tunnel is calculated. The results demonstrate that the effect of Rayleigh wave on the seismic response of shallow-buried underground structures can not be ignored. And it shows that the deformation is mainly the bending and the amplitude of the strain at the top of the structure is about 2 times bigger than the corresponding bottom point.The numerical model suggested is then applied to an experimental model and the computational results are compared with shaking table test results. The numerical results and the test results match quite well. The feasibility and efficiency of the proposed FEM model is validated by the comparison, and it can be adopted for further investigations.Reliability-based design is the final goal of structural design. This paper extends the physical stochastic earthquake model, using the sprectral representation method, to get the stochastic inconsistent excitation. Then based on the probability density evolution method (PDEM), the probability desity surface is calculated. Furthermore, the failure criterion of utility tunnel is analyzed and the equivalent extreme value event is introduced and applied to calculate the seismic reliability.更多还原