共查询到20条相似文献，搜索用时 875 毫秒
1.
A general, rigorous, coupled Boundary Element–Finite Element (BE–FE) formulation is presented for non-linear seismic soil–structure interaction in two dimensions. The BE–FE method is applied to investigate the inelastic response of earth dams to transient SV waves. The dam body, consisting of heterogeneous materials modelled with a simple non-linear hysteretic model, is discretized with finite elements, whereas the elastic half-space is discretized with boundary elements. The study focuses on the combined effects of the material non-linearity and foundation flexibility. The results show the significant effect of the foundation flexibility in reducing the response through radiation of energy. For excitations with peak ground accelerations from 0·2gto 0·6g, the crest acceleration amplification ranges from 2·5 to 1·4 and seems to be comparable with field observations and results from other studies. Deamplification increasing with strain is reported at the lower part of the dam. The method is computationally powerful and can be used for efficient non-linear analysis of complex soil–structure systems. The efficiency of the BE–FE method allows further improvements with incorporation of a more advanced constitutive model and consideration of the generation and dissipation of pore-water pressures during the earthquake. © 1998 John Wiley & Sons, Ltd. 相似文献
2.
J. MullikenD.C. Rizos 《Soil Dynamics and Earthquake Engineering》2012,34(1):78-88
This work presents an efficient and stable methodology for the coupling of Finite Element Methods (FEM) and Boundary Element Methods (BEM) that is independent of the particular solver and allows for independent temporal discretizations among solvers. The approach satisfies explicitly compatibility conditions and equilibrium of forces at the contact interfaces. Although the proposed approach has been developed in view of the soil-rail-vehicle dynamic interaction problem in High Speed Rail applications, it is expressed in a general form applicable to any multi-domain, multi-phase transient problem. The method development and formulations are presented in detail. Verification and application studies demonstrate the accuracy, efficiency and versatility of the method for the direct time domain solution of dynamic problems including structure-structure interaction and soil-structure interaction. The proposed approach demonstrates high accuracy and efficiency to that of direct coupling solutions and more rigorous methods. 相似文献
3.
A study on the dynamic response of a railway track is presented via a 3-D formulation based on the frequency domain Boundary Element Method (BEM) and the Finite Element Method (FEM). The railway track consists of a group of surface, massive, rigid footings resting on a viscoelastic half-space and connected by an overlaying rail structure. The BEM, employing the full-space fundamental solutions and quadrilateral elements, is used for the simulation of the elastic half-space while the FEM is used to model the rigid footings and the rail superstructure. The loading function consists of a set of externally applied, harmonic or transient loads. Frequency as well as transient, by way of FFT, results are presented for various modes of vibration. Various numerical studies assess the through-the-soil interaction of the adjacent footings, the influence of soil damping, the effect of the overlaying structure on the frequency content of the system, and the effective simulation of an infinitely long railway track by a truncated one. 相似文献
4.
Linear in-plane soil–structure interaction in two dimensions (2D) is studied in fluid-saturated, poroelastic, layered half-space using the Indirect Boundary Element Method (IBEM). The structure is a shear wall supported by a rigid embedded foundation. Exact stiffness matrices for the soil layer and half-space, and Green׳s functions of uniformly distributed loads and pore pressure on an inclined line are derived. Results of the system response in the frequency domain are presented for the special case of single soil layer over bedrock, semi-circular foundation and zero seepage force. The effects of water saturation, soil porosity, depth of soil layer, rigidity contrast between layer and bedrock are investigated in the frequency domain for incident plane P- and SV waves. The results suggest that water saturation may cause increase of the system frequency by more than 10%. 相似文献
5.
6.
基于福建及邻近地区高密度的256个地磁场矢量(D、I、H分量)实测数据,结合全球陆地1km基准海拔高度工程的网格数据以及最新的第十二代国际地磁参考场模型(IGRF12),采用三维Taylor多项式模型构建了福建地区的地磁场模型.通过比较均方偏差(RMS)、磁场实际分布以及残差等,结果显示:(1)当三维Taylor模型的截断阶数(N)为2时,可基本反映N为6时的二维Taylor模型的拟合效果;(2)三维Taylor模型计算方便,精度较高,但较易出现龙格现象,因此在确定截断阶数时既要考虑模拟精度,还需要考虑边界效应问题. 相似文献
7.
In this paper the coupled equations governing the dynamic behavior of unsaturated soils are derived based on the poromechanics theory within the framework of the suction-based mathematical model presented by Gatmiri (1997) [Gatmiri B. Analysis of fully coupled behavior of unsaturated porous medium under stress, suction and temperature gradient. Final report of CERMES-EDF, 1997] and Gatmiri et al. (1998) [Gatmiri B, Delage P, Cerrolaza M, UDAM: a powerful finite element software for the analysis of unsaturated porous media. Adv Eng Software 1998; 29(1): 29–43]. In this formulation, the solid skeleton displacements, water pressure and air pressure are presumed to be independent variables. The Boundary Integral formulations as well as fundamental solutions for such a dynamic u–pw–pa theory are presented in this paper for the first time. The boundary integral equations are derived via the use of the weighted residuals method in a way that permits an easy discretization and implementation in a Boundary Element code. Also, the associated two dimensional (2D) fundamental solutions for such deformable porous medium with linear elastic behavior are derived in Laplace transform domain using the method of Hörmander. Finally, some numerical results are presented to show the accuracy of the proposed solutions. The derived results are verified analytically by comparison with the previously introduced corresponding fundamental solutions in elastodynamic limiting case. 相似文献
8.
A study on the dynamic response of three-dimensional flexible foundations of arbitrary shape, embedded in a homogenous, isotropic and linear elastic half-space is presented. Both massive and massless foundations are considered. The soil-foundation system is subjected to externally applied forces, and/or to obliquely incident seismic waves. The numerical method employed is a combination of the frequency domain Boundary Element Method, which is used to simulate the elastic soil medium, and the Finite Element Method, on the basis of which the stiffness matrix of the foundation is obtained. The foundation and soil media are combined by enforcing compatibility and equilibrium conditions at their common interface. Both relaxed and completely bonded boundary conditions are considered. The accuracy of the proposed methodology is partially verified through comparison studies with results reported in the literature for rigid embedded foundations. 相似文献
9.
A study of the effects of dam–foundation interaction on the response of earth dams to obliquely incident P and SV waves is presented. Emphasis is placed on the effects of the foundation flexibility and the spatial variability of the ground motion. The study is based on a rigorous hybrid numerical formulation that combines the efficiency and versatility of the Finite Element Method (FEM) and the ability of Boundary Element Method (BEM) to account for the radiation conditions at the far field. The developed hybrid method is very powerful and can be used efficiently to obtain accurate solutions of problems of complex geometry, material heterogeneity and, for time-domain analyses, material nonlinearity. The 2-D frequency-domain formulation is used here to investigate the response of infinitely long earth dams to obliquely incident P and SV waves. By accounting rigorously for the energy radiated back into the half-space, the study demonstrates the dramatic effect of the flexibility of the foundation rock in reducing the overall response of the dam. The effects of the spatial variability of the ground motion for P and SV waves travelling across the width of the dam are also important, but somewhat less pronounced than those of the foundation flexibility. 相似文献
10.
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
11.
A coupling model of Finite Elements (FEs), Boundary Elements (BEs), Infinite Elements (IEs) and Infinite Boundary Elements (IBEs) is presented for analysis of soil–structure interaction (SSI). The radiation effects of the infinite layered soil are taken into account by FE–IE coupling, while the underlying bed rock half-space is discretized into BE–IBE coupling whereby the non-horizontal bed rock surface can be accounted for. Displacement compatabilities are satisfied for all types of aforementioned elements. The equivalent linear approach is employed for approximation of nonlinearity of the near field soil. This model has some advantages over the current SSI program in considering the bed rock half-space and non-vertical wave incidence from the far field. Examples of verification demonstrate the applicability and accuracy of the method when compared with the FLUSH program. Finally, the effects of the relative modulus ratio Er/Es of rock and soil and the incident angles of non-vertical waves on the responses of the structure and the soil are examined. Copyright © 1999 John Wiley & Sons, Ltd. 相似文献
12.
A Fourier transform approach is applied to the transient analysis of dynamic soil–structure interaction under SH-motion. The governing equations are formulated in the frequency domain using a Finite Element–Boundary Element (FE–BE) coupling method. After solving the transformed problem, the transient solution is obtained using the discrete inverse Fourier transform with a fast Fourier transform algorithm. Two examples are presented in order to show the numerical performance of the proposed technique. 相似文献
13.
A simple analytical solution is presented for computing direct current (DC) electric field distortion due to a small cube in a homogeneous half-space, measured with a dipole–dipole array on the surface. Both the transmitter and the receiver may have any orientation; furthermore their position on the horizontal surface and the depth of the cube can be freely selected. It is shown that a simple approximate analytical method may replace more complicated 3D numerical modelling algorithms.
The approximation lies in the linearization of the problem: the secondary source (i.e. the cube) is considered as a system of three perpendicular electric dipoles. In spite of this first-order approximation, in the case of realistic depths z ( z R ≈0.1–0.5, where R is the transmitter–receiver distance), this approximate solution fits very well with true 3D numerical modelling results, and with analogue modelling results if a R ≤0.1, where a is the length of the side of the cube. Due to its simplicity, this method could be used for computing DC field distortion effects, estimating parameter-sensitivities, or even determining some initial models for further inversions. 相似文献
The approximation lies in the linearization of the problem: the secondary source (i.e. the cube) is considered as a system of three perpendicular electric dipoles. In spite of this first-order approximation, in the case of realistic depths z ( z R ≈0.1–0.5, where R is the transmitter–receiver distance), this approximate solution fits very well with true 3D numerical modelling results, and with analogue modelling results if a R ≤0.1, where a is the length of the side of the cube. Due to its simplicity, this method could be used for computing DC field distortion effects, estimating parameter-sensitivities, or even determining some initial models for further inversions. 相似文献
14.
本文提出了一种计算不规则起伏地形中SH波散射的有效方法——局域边界元法.本方法基于传统边界元法,为计算复杂地表散射问题提供了一种更加高效的解决方案.根据地震波满足的边界积分方程中牵引力格林函数的特性,我们将自由边界分解成水平部分和起伏部分.通过公式推导,可将水平部分的位移由起伏部分的位移通过格林函数线性叠加表示,因此只需对起伏部分的位移进行直接求解,从而极大地减少了待求解的未知数个数,显著提高了计算效率.通过与半圆形山谷SH波平面波入射的解析解比较,验证了方法的正确性.数值模型比较显示,局域边界元模拟结果与传统边界元数值解完全吻合,但是大幅提高了计算效率.因此,局域边界元法可以作为模拟不规则地形中地震波散射的有效工具. 相似文献
15.
Assessment of 2DH and pseudo‐3D modelling platforms in a large saline aquatic system: Lake Urmia,Iran 
下载免费PDF全文
下载免费PDF全文 The main objective of this paper is to provide comparative quantitative examinations on the capabilities of two‐dimensional horizontal and pseudo‐three‐dimensional (3D) modelling approaches for simulating spatial and temporal variability of the flow and salinity in Lake Urmia, Iran. The water quality in the lake has been an environmentally important subject partly because this shallow hypersaline aquatic ecosystem is considered to be one of the largest natural habitats of a unique multicellular organism, Artemia urmiana. This brine shrimp is the major food source for many of the protected and rare shorebirds that visit the lake. A. urmiana can grow and survive in certain ranges of salinity, and their disappearance could lead to an alteration of existing equilibria. The lake has also experienced considerable man‐made changes during the past three decades. A newly built crossing embankment almost divided the lake into two northern and southern halves. A relatively small opening of 1.25 km in the new embankment provides water connections between the two halves. As a result, the flow and salinity regimes have been significantly changed. This might have had adverse serious impacts on the lake ecosystem. In the current study, the two‐dimensional horizontal hydrodynamic model has been found to provide reasonable predictions for the flow regime in the lake, whereas its salinity predictions have not been consistent with the field observations. The pseudo‐3D model has produced results fairly close to the salinity measurements and its temporal and spatial variations. The pseudo‐3D model has been used for evaluating the embankment effects on the lake hydrodynamics and on the salinity conditions. The effectiveness of introducing a different number or length of openings in the embankment for restoring the pre‐embankment conditions has also been examined. These remedy options have been found not to offer substantial improvements to the lake's existing ecosystem. Copyright © 2013 John Wiley & Sons, Ltd. 相似文献
16.
A. Rodríguez-Castellanos E. Flores F.J. Sánchez-Sesma C. Ortiz-Alemán M. Nava-Flores R. Martin 《Soil Dynamics and Earthquake Engineering》2011
In this paper scattering of elastic waves in fluid–solid interfaces is investigated. We use the Indirect Boundary Element Method to study this wave propagation phenomenon in 2D models. Three models are analyzed: a first one with an interface between two half-spaces, one fluid on the top part and the other solid in the bottom; a second model including a fluid half-space above a layered solid; and finally, a third model with a fluid layer bounded by two solid half-spaces. The source, represented by Hankel's function of the second kind, is always applied in the fluid. This indirect formulation can give to the analyst a deep physical insight on the generated diffracted waves because it is closer to the physical reality and can be regarded as a realization of Huygens' principle. In any event, mathematically it is fully equivalent to the classical Somigliana's representation theorem. In order to gauge accuracy we test our method by comparing with an analytical solution known as Discrete Wave Number. A near interface pulse generates scattered waves that can be registered by receivers located in the fluid and it is possible to infer wave velocities of solids. Results are presented in both time and frequency domain, where several aspects related to the different wave types that emerge from this kind of problems are pointed out. 相似文献
17.
A comparison of two numerical models for the prediction of vibrations from underground railway traffic 总被引：2，自引：0，他引：2
S. Gupta M.F.M. Hussein G. Degrande H.E.M. Hunt D. Clouteau 《Soil Dynamics and Earthquake Engineering》2007,27(7):608-624
Two prediction models for calculating vibration from underground railways are developed: the pipe-in-pipe model and the coupled periodic finite element–boundary element (FE–BE) model.The pipe-in-pipe model is a semi-analytical three-dimensional model that accounts for the dynamic interaction between the track, the tunnel and the soil. The continuum theory of elasticity in cylindrical coordinates is used to model two concentric pipes: an inner pipe to represent the tunnel wall and an outer pipe to represent the surrounding soil. The tunnel and soil are coupled accounting for equilibrium of stresses and compatibility of displacements at the tunnel–soil interface. This method assumes that the tunnel is invariant in the longitudinal direction and the problem is formulated in the frequency–wavenumber domain using a Fourier transformation. A track, formulated as an Euler–Bernoulli beam, is then coupled to this model. Results are transformed to the space domain using the inverse Fourier transform.The coupled periodic FE–BE model is based on a subdomain formulation, where a boundary element method is used for the soil and a finite element method for the tunnel. The Craig–Bampton substructuring technique is used to efficiently incorporate the track in the tunnel. The periodicity of the tunnel is exploited using the Floquet transformation to formulate the track–tunnel–soil interaction problem in the frequency–wavenumber domain and to compute the wave field radiated into the soil.An invariant concrete tunnel, embedded in a homogeneous full space is analyzed using both approaches. The pipe-in-pipe model offers an exact solution to this problem, which is used to validate the coupled periodic FE–BE model. The free field response due to a harmonic load in the tunnel is predicted and results obtained with both models are compared. The advantages and limitations of both models are highlighted. The coupled periodic FE–BE model has a greater potential as it can account for the complex periodic geometry of the tunnel and the layering in a soil medium. The effect of coupling a floating slab to the tunnel–soil system is also studied with both models by calculating the insertion gain. 相似文献
18.
María Charco José Fernández Francisco Luzón Kristy F. Tiampo John B. Rundle 《Pure and Applied Geophysics》2007,164(4):865-878
Surface displacements and gravity changes due to volcanic sources are influenced by medium properties. We investigate topographic,
elastic and self-gravitation interaction in order to outline the major factors that are significant in data modelling. While
elastic-gravitational models can provide a suitable approximation to problems of volcanic loading in areas where topographic
relief is negligible, for prominent volcanoes the rough topography could affect deformation and gravity changes to a greater
extent than self-gravitation. This fact requires the selection, depending on local relief, of a suitable model for use in
the interpretation of surface precursors of volcanic activity. We use the three-dimensional Indirect Boundary Element Method
to examine the effects of topography on deformation and gravity changes in models of magma chamber inflation/deflation. Topography
has a significant effect on predicted surface deformation and gravity changes. Both the magnitude and pattern of the geodetic
signals are significantly different compared to half-space solutions. Thus, failure to account for topographic effects in
areas of prominent relief can bias the estimate of volcanic source parameters, since the magnitude and pattern of deformation
and gravity changes depend on such effects. 相似文献
19.
An efficient discrete model for predicting the dynamic through-the-soil interaction between adjacent rigid, surface foundations supported by a homogeneous, isotropic and linear elastic half-space is presented. The model utilizes frequency-independent springs and dashpots, and the foundation mass, for the consideration of soil–foundation interaction. The through-the-soil coupling of the foundations is attained by frequency-independent stiffness and damping functions, developed in this work, that interconnect the degrees of freedom of the entire system of foundations. The dynamic analysis of the resulting coupled system is performed in the time domain and includes the time lagging effects of coupled dynamic input due to wave propagation using an appropriate modification of the Wilson-θ method. The basic foundation interaction model is also extended to the evaluation of coupled building-foundation systems. © 1998 John Wiley & Sons, Ltd. 相似文献
20.
传统三维大地电磁各向异性模拟均是基于规则六面体网格,计算精度有限且较难拟合复杂地质条件.本文采用面向目标自适应非结构矢量有限元法,对三维大地电磁各向异性介质进行模拟.首先从电场双旋度方程出发,利用伽辽金方法建立变分方程;然后利用电流密度连续性条件构建适合大地电磁各向异性问题的加权后验误差估计方法,实现面向目标的网格自适应正演;最后通过典型算例分析各向异性对网格自适应和大地电磁响应的影响特征以及各向异性的识别方法.本文算法能够高精度地拟合起伏地表和任意各向异性介质,适用于分析复杂地电条件大地电磁响应特征,为提高大地电磁资料解释水平提供了理论基础. 相似文献