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CONTENTS
Volume 1, Number 1, March 2012
 

Abstract
The problem of laterally loaded piles is particularly a complex soil-structure interaction problem. The flexural stresses developed due to the combined action of axial load and bending moment must be evaluated in a realistic and rational manner for safe and economical design of pile foundation. The paper reports the finite element analysis of pile groups. For this purpose simplified models along the lines similar to that suggested by Desai et al. (1981) are used for idealizing various elements of the foundation system. The pile is idealized one dimensional beam element, pile cap as two dimensional plate element and the soil as independent closely spaced linearly elastic springs. The analysis takes into consideration the effect of interaction between pile cap and soil underlying it. The pile group is considered to have been embedded in cohesive soil. The parametric study is carried out to examine the effect of pile spacing, pile diameter, number of piles and arrangement of pile on the responses of pile group. The responses considered include the displacement at top of pile group and bending moment in piles. The results obtained using the simplified approach of the F.E. analysis are further compared with the results of the complete 3-D F.E. analysis published earlier and fair agreement is observed in the either result.

Key Words
pile; pile cap; spacing; diameter; series arrangement; parallel arrangement; simplified models

Address
H.S. Chore: Department of Civil Engineering, Datta Meghe College of Engineering, Sector-3, Airoli, Navi Mumbai-400 708, India
R.K. Ingle: Department of Applied Mechanics, Visvesvaraya National Institute of Technology (VNIT), Nagpur-440 010, India
V.A. Sawant: Department of Civil Engineering, Indian Institute of Technology Roorkee, Roorkee-247 667, India

Abstract
In this work, the iterative coupling of finite element and boundary element methods for the investigation of coupled fluid-fluid, solid-solid and fluid-solid wave propagation models is reviewed. In order to perform the coupling of the two numerical methods, a successive renewal of the variables on the common interface between the two sub-domains is performed through an iterative procedure until convergence is achieved. In the case of local nonlinearities within the finite element sub-domain, it is straightforward to perform the iterative coupling together with the iterations needed to solve the nonlinear system. In particular, a more efficient and stable performance of the coupling procedure is achieved by a special formulation that allows to use different time steps in each sub-domain. Optimized relaxation parameters are also considered in the analyses, in order to speed up and/or to ensure the convergence of the iterative process.

Key Words
wave propagation; iterative coupling; finite element method; boundary element method; multidomain decomposition; different time-steps; nonlinear calculations

Address
Delfim Soares Jr. : Structural Engineering Department, Federal University of Juiz de Fora, CEP 36036-330 Juiz de Fora, MG, Brazil

Abstract
This study intends to explore dynamic interaction behaviors between actively controlled maglev vehicle and guideway girders by considering the nonlinear forms of electromagnetic force and current exactly. For this, governing equations for the maglev vehicle with ten degrees of freedom are derived by considering the nonlinear equation of electromagnetic force, surface irregularity, and the deflection of the guideway girder. Next, equations of motion of the guideway girder, based on the mode superposition method, are obtained by applying the UTM-01 control algorithm for electromagnetic suspension to make the maglev vehicle system stable. Finally, the numerical studies under various conditions are carried out to investigate the dynamic characteristics of the maglev system based on consideration of the linear and nonlinear electromagnetic forces. From numerical simulation, it is observed that the dynamic responses between nonlinear and linear analysis make little difference in the stable region. But unstable responses in nonlinear analysis under poor conditions can sometimes be obtained because the nominal air-gap is too small to control the maglev vehicle stably. However, it is demonstrated that this unstable phenomenon can be removed by making the nominal air-gap related to electromagnetic force larger. Consequently it is judged that the nonlinear analysis method considering the nonlinear equations of electromagnetic force and current can provide more realistic solutions than the linear analysis.

Key Words
maglev; guideway; dynamic interaction; electromagnetic suspension (ems); active control; surface irregularity

Address
Dong-Ju Min and Moon-Young Kim :Department of Civil and Environmental Engineering, Sungkyunkwan University,
Cheoncheon-Dong, Jangan-gu, Suwon 440-746, S. Korea
Jun-Seok Lee :Civil Engineering Team, Samsung C&T Corporation, Seoch02-Dong, Seocho-Gu, Seoul 137-956, S. Korea

Abstract
The available analytical methods of analysis for laterally loaded piles in level ground cannot be directly applied to such piles in sloping ground. With the commercially available software, the simulation of the appropriate field condition is a challenging task, and the results are subjective. Therefore, it becomes essential to understand the process of development of a user-framed numerical formulation, which may be used easily as per the specific site conditions without depending on other indirect methods of analysis as well as on the software. In the present study, a detailed three-dimensional finite element formulation is presented for the analysis of laterally loaded piles in sloping ground developing the 18 node triangular prism elements. An application of the numerical formulation has been illustrated for the pile located at the crest of the slope and for the pile located at some edge distance from the crest. The specific examples show that at any given depth, the displacement and bending moment increase with an increase in slope of the ground, whereas they decrease with increasing edge distance.

Key Words
finite element analysis; lateral load; pile; sloping ground; edge distance

Address
Vishwas A. Sawant : Department of Civil Engineering, Indian Institute of Technology, Roorkee, India
Sanjay Kumar Shukla : Discipline of Civil Engineering, School of Engineering, Edith Cowan University, Perth, WA 6027, Australia

Abstract
In the present paper, the three-dimensional model of a typical rectangular concrete tank is excited using an artificial and a natural three components earthquake ground motion and the staggered displacement method is utilized for solving the coupled problem of the tank-contained liquid system in time domain. In the proposed method, surface sloshing of the liquid is taken into account in addition to the impulsive term and the appropriate damping values are applied on both of them. The resulted responses are compared with those obtained from the ABAQUS finite element software. It is found that the convective term affects responses extensively and must be considered in seismic design/safety assessment of storage tanks. In addition, the utilized method for solving the coupled problem is stable during the conducted general dynamic analyses and is able to capture the expected phenomena.

Key Words
tank-contained liquid interaction; staggered displacement method; surface sloshing; multicomponent ground motion; rectangular concrete tank

Address
H. Mirzabozorg : Department of Civil Engineering, K. N. Toosi University of Technology, Tehran, Iran
M.A. Hariri-Ardebili : Department of Civil, Environmental and Architectural Engineering, University of Colorado, Boulder, USA
R. Nateghi A. : Department of Civil Engineering, K. N. Toosi University of Technology, Tehran, Iran

Abstract
We present a monolithic semi-implicit algorithm for solving fluid-structure interaction problem at small structural displacements. The algorithm uses one global mesh for the fluid-structure domain obtained by gluing the fluid and structure meshes which are matching on the interface. The continuity of velocity at the interface is automatically satisfied and the continuity of stress does not appear explicitly in the global weak form due to the action and reaction principle. At each time step, we have to solve a monolithic system of unknowns velocity and pressure defined on the global fluid-structure domain. Numerical results are presented.

Key Words
fluid-structure interaction; monolithic approach; semi-implicit algorithm

Address
Soyibou Sy and Cornel Marius Murea :Laboratoire de Mathematiques, Informatique et Applications, Universite de Haute Alsace, Mulhouse, France


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