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A new sloshing analysis method for rectangular tank systems with a submerged structure are proposed by using the velocity potential and the linear water wave theory. The velocity potential functions are obtained by decomposing the surface wave into a wall-induced wave, reflected and transmitted waves, and a scattered wave. A simplified method using a response spectrum for zero damping is also proposed. The results of the simplified method are in good agreement with those of the analytical method. The sloshing response of the fluid-structure system is found to be very sensitive to the characteristics of the ground motion and the configuration of the system. Under typical earthquakes, the submerged structure shows a tendency to decrease sloshing amplitude, hydrodynamic pressure, and base shear, while it shows a tendency to increase the overturning moment. For the ground excitation dominated by low-frequency contents, the sloshing response increases significantly and the contribution of the higher sloshing modes increases. Copyright © 1999 John Wiley & Sons, Ltd. 相似文献
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为了研究高阶晃动振型对LNG储罐地震响应的影响,考虑高阶晃动振型,建立LNG储罐的简化力学模型,推导LNG储罐的运动控制方程,给出了LNG储罐的基底剪力、倾覆弯矩和储罐内液体晃动波高的表达式。以某16×104 m3 LNG储罐为例,采用大型通用有限元分析软件ADINA System对其进行有限元模型分析,验证其修正模型的有效性,结果表明:高阶晃动振型对基底剪力和倾覆弯矩几乎无影响,但对晃动波高影响显著,尤其是长周期地震动作用下,并且考虑高阶晃动振型的晃动波高存在延时效应。提出的简化力学模型修正公式与有限元分析结果吻合较好,可以准确地预测LNG储罐地震响应。 相似文献
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Nonlinear behavior of liquid sloshing inside a partially filled rectangular tank is investigated. The nonlinearity in the numerical modeling of the liquid sloshing originates from the nonlinear terms of the governing equations of the fluid flow and the liquid free surface motion as a not known boundary condition. The numerical simulations are performed for both linear and nonlinear conditions. The computed results using linear conditions are compared with readily available exact solution. In order to verify the results of the nonlinear numerical solution, a series of the shaking table tests on rectangular tank were conducted. Having verified linear and nonlinear numerical models, they are used for computation of near wall sloshing height at a series of real scale tanks (with various dimensions) under the both harmonic and earthquake base excitation. Finally, the nonlinear effects on liquid sloshing modeling are discussed and the practical limitations of the linear solution in evaluating the response of seismically excited liquids are also addressed. 相似文献
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A two-dimensional Galerkin finite element model for water flow in variably saturated soil is presented. A fourth-order Runge-Kutta time integration method is employed which allows use of time steps at least 2 times greater than for a traditional finite difference approximation of time derivatives. For short total simulation times computer execution costs for the Runge-Kutta method are greater than for the finite difference approximation due to the start up cost of the Runge-Kutta method, but for longer simulation times the Runge-Kutta method requires considerably less computational effort even when automatic time-step adjustment is used with the finite difference procedure. A comparison of the method of influence coefficients and 2 × 2 Gaussian integration to compute element matrices indicates that the influence coefficient method reduces total execution time to 60% of that required for numerical quadrature. Computed pressure heads using the influence coefficient method and numerical integration are found to be in close agreement with each other even under conditions of highly non-linear soil properties in a heterogeneous domain. Fluxes computed by the two methods are also generally in close agreement except under extremely non-linear conditions when some deviations were observed at short simulation times. 相似文献
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针对地下结构抗震分析中应用广泛的波动方法与振动方法,从物理方程和有限元格式出发,明确了两种方法的区别与联系。通过标准数值试验,证明了振动方法是波动方法采用下卧刚性基岩假设和地层水平无限延伸假设,仅考虑SV波垂直向上入射的一种特例。采用波动方法模拟弹性地基,对比振动方法结果,表明弹性地基和刚性地基上地表位移响应和隧道结构内力响应均有显著差异。建议应根据具体场地条件,选择振动或波动方法进行地下结构抗震设计研究。 相似文献
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Elena Zhebel Sara Minisini Alexey Kononov Wim A. Mulder 《Geophysical Prospecting》2014,62(5):1111-1125
The finite‐difference method on rectangular meshes is widely used for time‐domain modelling of the wave equation. It is relatively easy to implement high‐order spatial discretization schemes and parallelization. Also, the method is computationally efficient. However, the use of finite elements on tetrahedral unstructured meshes is more accurate in complex geometries near sharp interfaces. We compared the standard eighth‐order finite‐difference method to fourth‐order continuous mass‐lumped finite elements in terms of accuracy and computational cost. The results show that, for simple models like a cube with constant density and velocity, the finite‐difference method outperforms the finite‐element method by at least an order of magnitude. Outside the application area of rectangular meshes, i.e., for a model with interior complexity and topography well described by tetrahedra, however, finite‐element methods are about two orders of magnitude faster than finite‐difference methods, for a given accuracy. 相似文献
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T. Novo H. Varum F. Teixeira-Dias H. Rodrigues M. Falcao Silva A. Campos Costa L. Guerreiro 《Bulletin of Earthquake Engineering》2014,12(2):1007-1024
This paper is focused on the study of an earthquake protection system, the tuned liquid damper (TLD), which can, if adequately designed, reduce earthquake demands on buildings. This positive effect is accomplished taking into account the oscillation of the free surface of a fluid inside a tank (sloshing). The behaviour of an isolated TLD, subjected to a sinusoidal excitation at its base, with different displacement amplitudes, was studied by finite element analysis. The efficiency of the TLD in improving the seismic response of an existing building, representative of modern architecture buildings in southern European countries was also evaluated based on linear dynamic analyses. 相似文献
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The finite‐volume technique is used to solve the two‐dimensional shallow‐water equations on unstructured mesh consisting of quadrilateral elements. In this paper the algorithm of the finite‐volume method is discussed in detail and particular attention is paid to accurately representing the complex irregular computational domain. The lower Yellow River reach from Huayuankou to Jiahetan is a typical meandering river. The generation of the computational mesh, which is used to simulate the flood, is affected by the distribution of water works in the river channel. The spatial information about the two Yellow River levee, the protecting dykes, and those roads that are obviously higher than the ground, need to be used to generate the computational mesh. As a result these dykes and roads locate the element interfaces of the computational mesh. In the model the finite‐volume method is used to solve the shallow‐wave equations, and the Osher scheme of the empirical function is used to calculate the flux through the interface between the neighbouring elements. The finite‐volume method has the advantage of using computational domain with complex geometry, and the Osher scheme is a method based on characteristic theory and is a monotone upwind numerical scheme with high resolution. The flood event with peak discharge of 15 300 m3/s, occurring in the period from 30 July to 10 August 1982, is simulated. The estimated result indicates that the simulation method is good for routing the flood in a region with complex geometry. Copyright © 2002 John Wiley & Sons, Ltd. 相似文献
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This paper reports on the results of a study conducted on tanks partially filled with water, representing tuned liquid dampers (TLD), subjected to both 1D and 2D horizontal excitations. The sloshing response of the water in the tank is characterized by the free surface motion, the resulting base shear force, and evaluation of the energy dissipated by the sloshing water. A 1D non‐linear flow model capable of simulating a TLD equipped with damping screens is employed to model a 2D TLD. Application of this particular model requires the assumption that the response is decoupled and can be treated as the summation of two independent 1D TLDs. Results from the non‐linear flow model are compared with the 2D experimental shake table test results leading to a validation of the decoupled response assumption. This attractive decoupled response property allows square and rectangular tanks to be used as 2D TLDs, which can simultaneously reduce the dynamic response of a structure in two perpendicular modes of vibration. Copyright © 2005 John Wiley & Sons, Ltd. 相似文献
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A common effective method to reduce the seismic response of liquid storage tanks is to isolate them at base using base-isolation systems. It has been observed that in many earthquakes, the foregoing systems significantly affect on the whole system response reduction. However, in exceptional cases of excitation by long-period shaking, the base-isolation systems could have adverse effects. Such earthquakes could cause tank damage due to excessive liquid sloshing. Therefore, the numerical seismic response of liquid storage tanks isolated by bilinear hysteretic bearing elements is investigated under long-period ground motions in this research. For this purpose, finite shell elements for the tank structure and boundary elements for the liquid region are employed. Subsequently, fluid–structure equations of motion are coupled with governing equation of base-isolation system, to represent the whole system behavior. The governing equations of motion of the whole system are solved by an iterative and step-by-step algorithm to evaluate the response of the whole system to the horizontal component of three ground motions. The variations of seismic shear forces, liquid sloshing heights, and tank wall radial displacements are plotted under various system parameters such as the tank geometry aspect ratio (height to radius), and the flexibility of the isolation system, to critically examine the effects of various system parameters on the effectiveness of the base-isolation systems against long-period ground motions. From these analyses, it may be concluded that with the installation of this type of base-isolation system in liquid tanks, the dynamic response of tanks during seismic ground motions can be considerably reduced. Moreover, in the special case of long-period ground motions, the seismic response of base-isolated tanks may be controlled by the isolation system only at particular conditions of slender and broad tanks. For the case of medium tanks, remarkable attentions would be required to be devoted to the design of base-isolation systems expected to experience long-period ground motions. 相似文献
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传统有限差分方法在处理起伏地表时存在一些困难,而坐标变换法可将起伏地表映射为水平地表以克服此缺点.但同时,地下构造被变换得更加复杂,导致了波传播和成像的不准确.本文提出了一种分层的坐标变换方法,并应用到了弹性波逆时偏移中,此方法既可以克服起伏地表的影响,又可以不破坏地下构造.波场正向延拓、逆时延拓和分离是在辅助坐标系下完成的,而成像是在笛卡尔坐标系下完成的.通过对简单起伏模型和中原起伏模型的试算证明了本文提出方法的准确性.同时,对两种极端起伏地层高程不准确的情况进行测试可以看出:分层坐标变换逆时偏移方法的成像效果远好于传统坐标变换方法. 相似文献
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为研究考虑桩土相互作用的储液罐的动力响应及长周期地震波对储液晃动、储罐提离的影响,根据量纲分析法设计了桩-土-储罐模型进行了振动台试验。试验中采用4条基岩波、4条地表波进行振动台试验。试验显示基岩波与地表波输入时,体系变化规律基本一致,其结果表明:土体地表加速度被放大,且输入加速度峰值增加,地表加速度放大倍数减小;一般地震波时,随着输入加速度峰值的增加,储液晃动波高大致呈线性增加。长周期地震波下则为非线性增加,且晃动波较大。此外,液体产生的晃动波高与储罐类型相关。细高型储罐产生的波高稍大;储罐提离高度随着输入加速度峰值的增加呈非线性增长。长周期地震波激励下,储罐提离高度小于一般地震波时的提离高度。细高型储罐在长短周期地震波激励下,提离高度较为接近,而一般储罐在两种地震波激励下,提离高度相差较大。细高型储罐提离高度大于一般储罐的提离高度。建议在储罐设计时考虑长周期地震波的影响。 相似文献
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Seismic wavefield modeling in media with fluid-filled fractures and surface topography 总被引：3，自引：0，他引：3
We present a finite difference (FD) method for the simulation of seismic wave fields in fractured medium with an irregular (non-flat) free surface which is beneficial for interpreting exploration data acquired in mountainous regions. Fractures are introduced through the Coates-Schoenberg approach into the FD scheme which leads to local anisotropic properties of the media where fractures are embedded. To implement surface topography, we take advantage of the boundary-conforming grid and map a rectangular grid onto a curved one. We use a stable and explicit second-order accurate finite difference scheme to discretize the elastic wave equations (in a curvilinear coordinate system) in a 2D heterogeneous transversely isotropic medium with a horizontal axis of symmetry (HTI). Efficiency tests performed by different numerical experiments clearly illustrate the influence of an irregular free surface on seismic wave propagation in fractured media which may be significant to mountain seismic exploration. The tests also illustrate that the scattered waves induced by the tips of the fracture are re-scattered by the features of the free surface topography. The scattered waves provoked by the topography are re-scattered by the fractures, especially Rayleigh wave scattering whose amplitudes are much larger than others and making it very difficult to identify effective information from the fractures. 相似文献
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A hybrid analytical and FEM is proposed to investigate the nonlinear sloshing in a floating‐roofed oil storage tank under long‐period seismic ground motion. The tank is composed of a rigid cylindrical wall and a flat bottom, whereas the floating roof is treated as an elastic plate undergoing large deflection. The contained liquid is assumed to be inviscid and incompressible, and the flow is assumed to be irrotational. The method of analysis is based on representation of the liquid motion by superposing the analytical modes that satisfy the Laplace equation and the rigid wall and bottom boundary conditions. The FEM is then applied to solve the remaining kinematic and dynamic boundary conditions at the moving liquid surface coupled with the nonlinear equation of motion of the floating roof. This requires only the discretization of the liquid surface and the floating roof into finite elements, thus leading to a computationally efficient and accurate method compared with full numerical analysis. As numerical examples to illustrate the applicability of the proposed method, two oil storage tanks with single‐deck type floating roofs damaged during the 2003 Tokachioki earthquake are studied. It is shown that the nonlinear oscillation modes with the circumferential wave numbers 0, 2 and 3 caused by the finite liquid surface elevation as well as the membrane action due to large deflection of the deck produce excessively large stresses in the pontoon, which may cause the catastrophic failure of pontoon followed by the submergence of the roof. Copyright © 2012 John Wiley & Sons, Ltd. 相似文献
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复频移完全匹配层(Complex Frequency-Shifted PML,CFS-PML)在长时间时域计算中对凋落波、倏失波具有好的吸收效果,并被广泛应用于时域有限差分模拟中.而本文采用卷积方法将CFS-PML应用于时域有限元求解GPR波动方程的数值模拟中.论文以TM波为例,推导了基于CPML(Convolutional PML)边界的时域有限元GPR波动方程求解公式,采用Newmark-β方法对时间导数进行离散,有效改善了时域有限元GPR数值计算程序的稳定性.并以狭长模型为例,开展了CPML边界中关键参数m、R和κ的选取实验,通过对比反射误差大小确定了综合最优参数组合.相同时刻UPML与CPML波场快照、3个检测点的反射误差比较,说明CPML较UPML具有更好的吸收效果.最后,采用非规则四边形网格对1个复杂GPR模型进行剖分,应用加载CPML边界条件的FETD程序对该模型进行了正演,得到了二维剖面法、宽角法正演GPR剖面图,说明非规则四边形对复杂模型的良好适应性,基于CPML边界条件的FETD可有效减少边界反射误差,能实现对任意复杂不规则模型的正演模拟. 相似文献
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为减少直接分析三维大尺度复杂土-结构动力相互作用问题的计算量,提高计算效率,本文直接从波动方程出发,提出了较常规子结构法更简单的两步简化计算过程,即第一步简化上部复杂结构体系为集中质量杆系模型,并求基础处等效输入,第二步通过等效输入求上部结构各位置的动力反应.其中第一步计算主要采用集中质量显式有限单元法结合局部透射人工... 相似文献
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Kyung Hwan Cho Moon Kyum Kim Yun Mook Lim Seong Yong Cho 《Soil Dynamics and Earthquake Engineering》2004,24(11):839-852
The seismic response analysis of a base-isolated liquid storage tank on a half-space was examined using a coupling method that combines the finite elements and boundary elements. The coupled dynamic system that considers the base isolation system and soil–structure interaction effect is formulated in time domain to evaluate accurately the seismic response of a liquid storage tank. Finite elements for a structure and boundary elements for liquid are coupled using equilibrium and compatibility conditions. The base isolation system is modeled using the biaxial hysteretic element. The homogeneous half-space is idealized using the simple spring-dashpot model with frequency-independent coefficients. Some numerical examples are presented to demonstrate accuracy and applicability of the developed method.Consequently, a general numerical algorithm that can analyze the dynamic response of base-isolated liquid storage tanks on homogeneous half-space is developed in three-dimensional coordinates and dynamic response analysis is performed in time domain. 相似文献
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A tuned liquid damper (TLD), which consists of rigid tanks partially filled by liquid, is a type of passive control device relying upon liquid sloshing forces or moments to change the dynamical properties and to dissipate vibrational energy of a structure. An analytical non-linear model is proposed for a TLD using rectangular tanks filled with shallow liquid under pitching vibration, utilizing a shallow water wave theory. The model includes the linear damping of the sloshing liquid, which is an important parameter in the study of a TLD as it affects the efficiency of the TLD. Shaking table experiments were conducted for verification; good agreement between the analytical simulations and the experimental results was observed in a small excitation amplitude range. The simulations of TLD-structure interaction by using the proposed model show that the TLD can efficiently suppress resonant pitching vibration of a structure. It is also found that the effectiveness of a TLD for suppressing the pitching vibration depends not only on the mass of liquid in the TLD but also on the configuration of the liquid as well as upon the position where the TLD is located. If the configuration of the liquid, i.e. the liquid depth and the TLD tank size, is designed suitably, the TLD can have a large suppressing moment and can be very effective even with a small mass of liquid. 相似文献