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CONTENTS
Volume 30, Number 3, October20 2008
 

Abstract
Structural pipe-in-pipe cross-sections have significant potential for application in offshore oil and gas production systems because of their property that combines insulation performance with structural
strength in an integrated way. Such cross-sections comprise inner and outer thin walled pipes with the annulus between them fully filled by a selectable thick filler material to impart an appropriate
combination of properties. Structural pipe-in-pipe cross-sections can exhibit several different collapse mechanisms and the basis of the preferential occurrence of one over others is of interest. This paper presents an elastic analyses of a structural pipe-in-pipe cross-section when subjected to external hydrostatic pressure. It formulates and solves the static and elastic buckling problem using the variational principle of minimum potential energy. The paper also investigates a simplified formulation of the problem where the outer pipe and its contact with the filler material is considered as a ?pipe on an elastic foundation?. Results are presented to show the variation of elastic buckling pressure with the relative elastic modulus of the filler and pipe materials, the filler thickness and the thicknesses of the inner and outer pipes. The range of applicability of the simplified ?pipe on an elastic foundation? analysis is also presented. A brief review of the types of materials that could be used as the filler is combined with the results of the analysis to draw conclusions about elastic buckling behaviour of structural pipe-in-pipe cross-sections.

Key Words
pipe-in-pipe; elastic buckling; stress function; variational method.

Address
M. Sato: Graduate School of Engineering, Hokkaido University, Sapporo, Japan
M. H. Patel: School of Engineering, Cranfield University, Cranfield, United Kingdom
F. Trarieux: School of Engineering, Cranfield University, Cranfield, United Kingdom

Abstract
This paper presents an exact integration for the hypersingular boundary integral equation of two-dimensional elastostatics. The boundary is discretized by straight segments and the physical variables are approximated by discontinuous quadratic elements. The integral for the hypersingular boundary integral equation analysis is given in a closed form. It is proven that using the exact integration for
discontinuous boundary element, the singular integral in the Cauchy Principal Value and the hypersingular integral in the Hadamard Finite Part can be obtained straightforward without special treatment. Two
numerical examples are implemented to verify the correctness of the derived exact integration.

Key Words
hypersingular boundary integral equation; exact integration; singular integral in CPV; hypersingular integral in HFP.

Address
Xiaosong Zhang: Dept. of Engineering Mechanics, Shijiazhuang Railway Institute, Shijiazhuang, 050043, Hebei Province, P. R. China
Xiaoxian Zhang: Dept. of Engineering, The University of Liverpool, Brodie Tower, Brownlow Street, Liverpool, L69 3GQ, U.K.

Abstract
This paper investigates the structural behavior of Korean traditional wooden structures on the basis of the structural analysis using the commercialized program, SAP 2000. All the structural systems
were analyzed, and the rotational stiffness at each joint was inferred from the experimental result for a half scale model of Bongjeong-sa (a temple in South Korea). In addition, the artificial control of analysis parameters was prevented because the structural analysis was focused on the realization of the most exact structural behavior of real structures. The analysis was carried out for the horizontal and vertical static loads, and all the secondary members were excluded in the structural analysis. The obtained results show that the resisting capacity of the primary structural system is greater than that of the expanding structural
system.

Key Words
traditional wooden structure; numerical modeling; structural analysis; lateral resisting capacity; moment distribution.

Address
Jong-Kook Hwang: Dept. of Traditional Architecture, National Univ. of Cultural Heritage, 430 Hapjung-ri,
Kyuam-myeon, Puyo, Chungchungnam-do 323-812, Korea
Samuel Kwak: Korean Minjok Leadership Academy, 1300 sosa-ri, Anheung-myeon, Hoengseong-gun,
Gangwon-do 225-823, Korea
Ji-Hyun Kwak: Dept. of Civil and Environmental Eng. KAIST, Daejeon 305-701, Korea

Abstract
Stress intensity factors for a planar crack parallel to a bimaterial interface are considered. The formulation leads to a system of hypersingular integral equations whose unknowns are three modes of
crack opening displacements. In the numerical analysis, the unknown displacement discontinuities are approximated by the products of the fundamental density functions and polynomials. The numerical
results show that the present method yields smooth variations of stress intensity factors along the crack front accurately. The mixed mode stress intensity factors are indicated in tables and figures with varying the shape of crack, distance from the interface, and elastic constants. It is found that the maximum stress intensity factors normalized by root area are always insensitive to the crack aspect ratio. They are given in a form of formula useful for engineering applications.

Key Words
hypersingular integral equation; stress intensity factor; bimaterial; crack.

Address
Chunhui Xu, Taiyan Qin and Li Yuan: College of Science, China Agricultural University, Beijing 100083, P.R. China
Nao-Aki Noda: Dept. of Mechanical Engineering, Kyushu Institute of Technology, Kitakyushu, 804-8550, Japan

Abstract
A framework for multi-platform analytical and multi-component hybrid (testing-analysis) simulations is described in this paper and illustrated with several application examples. The framework allows the integration of various analytical platforms and geographically distributed experimental facilities into a comprehensive pseudo-dynamic hybrid simulation. The object-oriented architecture of the
framework enables easy inclusion of new analysis platforms or experimental models, and the addition of a multitude of auxiliary components, such as data acquisition and camera control. Four application examples are given, namely; (i) multi-platform analysis of a bridge with soil and structural models, (ii) multiplatform, multi-resolution analysis of a high-rise building, (iii) three-site small scale frame hybrid simulation, and (iv) three-site large scale bridge hybrid simulation. These simulations serve as illustrative examples of collaborative research among geographically distributed researchers employing different analysis platforms and testing equipment. The versatility of the framework, ease of including additional modules and the wide application potential demonstrated in the paper provide a rich research environment for structural and geotechnical engineering.

Key Words
hybrid simulation; multi-platform analysis; pseudo-dynamic testing.

Address
Oh-Sung Kwon: Dept. of Civil, Architectural, and Environmental Engineering, Missouri University of Science and Technology, Rolla, MO, 65409, USA
Amr S. Elnashai: William J. & Elaine F. Hall Endowed Professor of Civil & Environmental Engineering, Director of the Mid-America Earthquake Center, University of Illinois at Urbana-Champaign, Urbana, IL 61801, USA
Billie F. Spencer: Nathan M. and Anne M. Newmark Endowed Chair, Department of Civil and Environmental Engineering, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801, USA

Abstract
The purpose of this paper is to propose a simple analysis method of axial deformation of base-isolation rubber bearings in a building subjected to earthquake loading and present its applicability to
the analysis of the bound of the aspect ratio of base-isolated buildings. The base shear coefficient is introduced as a key parameter for the bound analysis. The bound of the aspect ratio of base-isolated
buildings is analyzed based on the relationship of the following four quantities; (i) ultimate state of the tensile stress of rubber bearings based on a proposed simple recursive analysis for seismic loading, (ii) ultimate state of drift of the base-isolation story for seismic loading, (iii) ultimate state of the axial compressive stress of rubber bearings under dead loads, (iv) prediction of the overturning moment at the base for seismic loading. In particular, a new recursive analysis method of axial deformation of rubber bearings is presented taking into account the nonlinear tensile behavior of rubber bearings and it is shown that the relaxation of the constraint on the ultimate state of the tensile stress of rubber bearings increases the limiting aspect ratio.

Key Words
base-isolation; bound of building aspect ratio; analysis of axial deformation of rubber bearing; recursive analysis; nonlinear uplift; base shear coefficient.

Address
J. Hino, S. Yoshitomi, M. Tsuji and I. Takewaki: Dept. of Urban & Environmental Engineering, Graduate School of Engineering, Kyoto University, Kyotodaigaku-Katsura, Nishikyo, Kyoto 615-8540, Japan

Abstract
An oscillator of two lumped masses linked through a vertical spring moves forward in the horizontal direction, initially at a certain height, over a horizontal Euler beam and descends on it due to
its own weight. Vibration of the beam and the oscillator is excited at the onset of the ensuing impact. The impact produced by the descending oscillator is assumed to be either perfectly elastic or perfectly plastic. If the impact is perfectly elastic, the oscillator bounces off and hits the beam a number of times as it moves forward in the longitudinal direction of the beam, exchanging its dynamics with that of the beam. If the impact is perfectly plastic, the oscillator (initially) sticks to the beam after its first impact and then may separate and reattach to the beam as it moves along the beam. Further events of separation and
reattachment may follow. This interesting and seemingly simple dynamic problem actually displays rather complicated dynamic behaviour and has never been studied in the past. It is found through simulated numerical examples that multiple events of separation and impact can take place for both perfectly elastic impact and perfectly plastic impact (though more of these in the case of perfectly elastic impact) and the dynamic response of the oscillator and the beam looks noisy when there is an event of impact because impact excites higher-frequency components. For the perfectly plastic impact, the oscillator can experience multiple events of consecutive separation from the beam and subsequent reattachment to it.

Key Words
jumping, moving oscillator, Euler beam, vibration, separation, impact.

Address
Luis Baeza: Dpto. de Ingenieria Mecanica, Universidad Politecnica de Valencia, Camino de Vera, 14 E46022 Valencia, Spain
Huajiang Ouyang: Dept. of Engineering, University of Liverpool, Liverpool L69 3GH, U.K.

Abstract
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Key Words
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Address
Anupam Chakrabarti: Dept. of Civil Engineering, Indian Institute of Technology Roorkee, Roorkee 247667, India


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