• Journal of the Earthquake Engineering Society of Korea
• /
• v.9 no.4 s.44
• /
• pp.67-74
• /
• 2005

This paper presents a new infinite element for modeling far-field region in dynamic analysis of a fluid-saturated two-phase medium. The infinite element method combined to the infinite element method has been effectively applied to several engineering problems where the full space or half-space medium should be modeled. However, the currently available infinite element for dynamic analysis of two-phase porous medium has a limitation that Pl and P2 waves can only be Included in shape function expressing behavior ol the body. In this paper, the infinite element method is extended to simulate arbitrary number of multi-component waves. For this purpose, the far-field of the porous medium is assumed to be a layered half-space, while the near-field Includes structures as well as irregular soil medium. The accuracy and effectiveness of the proposed element have demonstrated using 1-D and 2-D wave propagation problems.

• Proceedings of the Computational Structural Engineering Institute Conference
• /
• 1994.04a
• /
• pp.145-152
• /
• 1994

The dynamic interaction between tunnel structures and their surrounding soil medium due to impulse loading is investigated by a hybrid IEM/FEM methodology. A dynamic infinite element is developed for the efficient descretization of the far-field region of the unbounded soil medium. The shape functions of the infinite element are constructed based on the far-field solutions which are obtained by solving the 2-D elastic wave problems. Also they are devised to obtain a reasonable result over all frequency range. Numerical analysis is carried out to examine the response of the tunnel subjected to simple rectangular impulse. It is indicated that the results by the present method are in good accord with those by the boundary and finite element coupling method.

• Proceedings of the Computational Structural Engineering Institute Conference
• /
• 1994.04a
• /
• pp.128-136
• /
• 1994

In this study, dynamic boundary element method using mass matrix is derived, using fundamental solutions for the semi-infinite domain. In constituting boundary integral equations for the dynamic equilibrium condition, inertia term in the form of domain integral is transformed into boundary integral form. Corresponding system equations are derived, and a boundary element program is developed. In addition, equations for free vibration is formulated, and eigenvalue analysis is performed. The results from the dynamic boundary element analysis for a tunnel problem are compared with those from the finite element analysis. According to the comparison, boundary element method using mass matrix is consistent with the results of finite element method. Consequently, in tunnel vibration problems, it results in reasonable solution compared with other methods where relatively higher degree of freedoms are employed.

• Earthquakes and Structures
• /
• v.8 no.1
• /
• pp.275-304
• /
• 2015

The objective of this paper is to investigate the validity of transmitting boundaries in dynamic analysis of soil-structure interaction problems. As a case study, the proposed Baghdad metro line is considered. The information about the dimensions and the material properties of the concrete tunnel and surrounding soil were obtained from a previous study. A parametric study is carried out to investigate the effect of several parameters including the peak value of the horizontal component of earthquake displacement records and the frequency of the dynamic load. The computer program (Mod-MIXDYN) is used for the analysis. The numerical results are analyzed for three conditions; finite boundaries (traditional boundaries), infinite boundaries modelled by infinite elements (5-node mapped infinite element) presented by Selvadurai and Karpurapu, 1988), and infinite boundaries modelled by dashpot elements (viscous boundaries). It was found that the transmitting boundary absorbs most of the incident energy. The distinct reflections observed for the "fixed boundaries" disappear by using "transmitted boundaries". This is true for both cases of using viscous boundaries or mapped infinite elements. The type and location of the dynamic load represent two controlling factors in deciding the importance of using infinite boundaries. It was found that the results present significant differences when earthquake is applied as a base motion or a pressure load is applied at the surface ground. The peak value of the vertical displacement at nodes A, B, E and F (located at the tunnel's crown and side walls, and at the surface above the tunnel and at the surface 6.5 m away from tunnel's centre respectively) increases with the frequency of the surface pressure load for both cases 1 and 2 (traditional boundaries and mapped infinite elements respectively) while it decreases for case 3 (viscous boundaries). The modular ratio Ec/Es (modulus of elasticity of the concrete lining to that of the surrounding soil) has a considerable effect on the peak value of the horizontal displacement at node B (on the side wall of the tunnel lining) increase about (17.5) times, for the three cases (1, 2, and 3).

• Proceedings of the Computational Structural Engineering Institute Conference
• /
• 2008.04a
• /
• pp.14-19
• /
• 2008

This paper presents dynamic infinite element formulations which have been developed for soil-structure interaction analysis both in frequency and in time domains by the present authors during the past twenty years. Axisymmetric, 2D and 3D layered half-space soil media were considered in the developments. The displacement shape functions of the infinite elements were established using approximate expressions of analytical solutions in frequency domain to represent the characteristics of multiple waves propagating into the unbounded outer domain of the media. The proposed infinite elements were verified using benchmark examples, which showed that the present formulations are very effective for the soil-structure interaction analysis either in frequency or in time domain. Example applications to actual interaction problems are also given to demonstrate the capability and versatility of the present methodology.

• Proceedings of the Computational Structural Engineering Institute Conference
• /
• 1994.04a
• /
• pp.137-144
• /
• 1994

In this study, a new procedure for solving 2-D dynamic problems of semi-infinite medium in time domain by boundary element method (BEM) is presented. Efficient modelling of the far field region, infinite boundary elements are introduced. The shape function of the infinite boundary element is a combination of decay functions and Laguerre functions. Though the present shape functions have been developed for the time domain analysis, they may be also applicable to the frequency domain analysis. Through the response analysis in a 2-D half space under a uniformly distributed dynamic load, it has been found that an excellent accuracy can be achieved compared with the analytical solution

• Journal of the Korea Academia-Industrial cooperation Society
• /
• v.11 no.3
• /
• pp.1053-1058
• /
• 2010

Infinite element approach has been widely used to analysis soil-structure interaction, in which the soil domain is treated as infinite domain. However, most of the developed infinite element has been formulated in the frequency domain rather than the time domain to include the frequency contents of the earthquake or vibration wave. Due to that, those approaches have a critical limitation which is restricted to the linear elastic analysis. To main objective of this research is to develop the infinite element in the time domain to cooperate the inelastic soil and structure behavior. Developed infinite element is verified with the results of finite element analysis modeled in large domain. The nonlinear analysis also conducted to demonstrate the application of developed infinite element. Hence, based on above-mentioned statements, it can be concluded that the propose approach would assist for structure-seismic design.

• Structural Engineering and Mechanics
• /
• v.24 no.6
• /
• pp.683-698
• /
• 2006

The accurate dynamic analysis of concrete arch dams relies heavily on employing a three-dimensional semi-infinite fluid element. The usual method for calculating the impedance matrix of this fluid hyper-element is dependent on the solution of a complex eigen-value problem for each frequency. In the present study, an efficient procedure is proposed which simplifies this procedure amazingly, and results in great computational time saving. Moreover, the accuracy of this technique is examined thoroughly and it is concluded that efficient procedure is incredibly accurate under all practical conditions.

• KSCE Journal of Civil and Environmental Engineering Research
• /
• v.11 no.3
• /
• pp.47-58
• /
• 1991

This paper presents dynamic infinite elements for soil-structure interaction analysis. In order to discretize the far field of the unbounded soil media, axisymmetric infinite elements which are capable of propagating multi-waves are proposed. An efficient numerical integration scheme for constructing the element characteristic matrices of the infinite elements in developed based on Gauss-Laguerre quadrature. The efficiency of the infinite elements is demonstrated by comparing the computed impedances of rigid circular footings on an elastic half space and on a layered half spaces with those obtained analytically.

• Tunnel and Underground Space
• /
• v.12 no.3
• /
• pp.171-178
• /
• 2002

A dynamic analysis of a horseshoe_shaped tunnel near to cavity was performed to study the effect of the cavity on the dynamic behavior of the tunnel. In order to obtain the dynamic response of the tunnel embedded in a semi-infinite domain, a hybrid numerical technique was primarily developed. A dynamic fundamental solution in frequency domain for multi-layered half planes was derived and subsequently incorporated in the boundary element method. Coupling of the boundary element method for the far field with the finite element method for the near field is made by imposing compatibility condition of a displacement at the interface. The boundary element method is then coupled with the finite element method, which is utilized to model the near field including the tunnel and the cavity. In order to demonstrate the validity of the proposed technique, dynamic responses of single and multiply-layered semi-infinite structural systems are obtained by using the Kicker waveform and investigated in the limestone layer to find how the being and the location of the cavity affect the dynamic characteristics of the system.