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CONTENTS
Volume 6, Number 1, January 1998
 

Abstract
Experimental work undertaken to investigate the behaviour of lead-rubber bearings under compression and a combination of compression and shear or rotation has been reported on elsewhere. However, it is difficult to determine the state of stress within the bearings in terms of the applied forces and the interaction between the lead plug and the steel shims and elastomeric layers. Iri order to supply some of the missing information about the stress-strain state within the bearings, an analytical study using the finite element method was carried out. The available experimental results were used to validate the model and although agreement was not as good as expected (on account of difficulties in modelling the lead plug), the analyses did provide some information about the state of the stress within the bearing.

Key Words
bridge bearings, lead-rubber bearings, seismic isolation, finite element analysis, compression, shear, rotation

Address
Mori A, Japan Engn Consultants, Earthquake Disaster Mitigat Dept, Tokyo, Japan
Japan Engn Consultants, Earthquake Disaster Mitigat Dept, Tokyo, Japan
Univ Canterbury, Dept Civil Engn, Christchurch 1, New Zealand

Abstract
The method of pairwise comparison inherently contains information of ambiguity, fuzziness and conflict in design goals for a multiobjective structural design, This paper applies the principle of paired comparison so that the vaguely formulated problem can be modified and a set of numerically acceptable weight would reflect the relatively important degree of multiple objectives. This paper also presents a fuzzy global criterion method (FGCM(lambda)) included fuzzy constraints that coupled with the objective weighting rank obtained from the modified pairwise comparisons for fuzzy multiobjective optimization problems. Descriptions in sequence of this combined method and problem solving experiences are given in the current article. Multiobjective design examples of truss and mechanical spring structures illustrate this optimization process containing the revising judgement techniques.

Key Words
pairwise comparison, fuzzy global criterion method, global criterion method, multiobjective fuzzy optimization, weighting coefficient, structural design, consistent matrix

Address
Shih CJ, Tamkang Univ, Dept Mech Engn, Tamsui 25137, Taiwan
Tamkang Univ, Dept Mech Engn, Tamsui 25137, Taiwan
Yeu Tyan Machinery Mfg Co, Ctr Vehicle Design & Dev, Chang Hwa 51500, Taiwan

Abstract
The research and applications of numerical methods of design optimization on structural dynamic behaviors are presented in this paper. The emphasis is focused on the dynamic design optimization of aerospace structures, particularly those composed of composite laminate and sandwich plates. The methods of design modeling, sensitivity analysis on structural dynamic responses, and the optimization solution approaches are presented. The numerical examples of sensitivity analysis and dynamic structural design optimization are given to demonstrate the effectiveness of the numerical methods.

Key Words
sensitivity, dynamic optimization, aerospace structures

Address
Gu YX, Dalian Univ Technol, State Key Lab Struct Anal Ind Equipment, Res Inst Engn Mech, Dalian 116024, Peoples R China
Dalian Univ Technol, State Key Lab Struct Anal Ind Equipment, Res Inst Engn Mech, Dalian 116024, Peoples R China

Abstract
A state-of-the-art report on the new finite elements formulated by the addition of nonconforming displacement modes has been presented. The development of a series improved nonconforming finite elements for the analysis of plate and shell structures is described in the first part of this paper. These new plate and shell finite elements are established by the combined use of different improvement schemes such as; the addition of nonconforming modes, the reduced (or selective) integration, and the construction of the substitute shear strain fields. The improvement achieved may be attributable to the fact that the merits of these improvement techniques are merged into the formation of the new elements in a complementary manner. It is shown that the results obtained by the new elements give significantly improved solutions without any serious defects such as; the shear locking, spurious zero energy mode for the linear as well. as nonlinear benchmark problems. Recent developments in the transition elements that have a variable number of mid-side nodes and can be effectively used in the adaptive mesh refinement are presented in the second part. Finally, the nonconforming transition flat shell elements with drilling degrees of freedom are also presented.

Key Words
a state-of-the-art, nonconforming displacement modes, combined use of multiple techniques, selectively reduced integration, substitute shear strain fields, transition elements

Address
Choi CK, Korea Adv Inst Sci & Technol, Dept Civil Engn, Taejon 305701, South Korea
Korea Adv Inst Sci & Technol, Dept Civil Engn, Taejon 305701, South Korea
Youngdong Inst Technol, Dept Civil Engn, Youngdong 370800, South Korea
Res Inst Ind Sci & Technol, Steel Struct Technol Div, Seoul 135777, South Korea
Korea Railload Res Inst, Track Struct & Environm Div, Uiwang 437763, South Korea

Abstract
This paper presents dynamic responses of structures with sliding base which limits the translation of external loads from ground excitation. A discrete element model based on the discontinuous deformation analysis method is proposed to study this sliding boundary problem. The sliding base is simulated using sets of fictitious contact springs along the sliding interface. The set of contact spring is to translate friction force from ground to superstructure. Validity of the proposed model is examined by the closed-form solutions of an idealized mass-spring structural model subjected to harmonic ground excitation. This model is also applied to a problem of a three-story structural model subjected to the ground excitation of 1940 El Centro earthquake. Analyses of both sliding-base and fixed-base conditions are performed as comparisons. This study shows that using this model can simulate the dynamic response of a sliding structure with frictional cut-off quite accurately. Results reveal that lowering the frictional coefficient-of the sliding joint will reduce the peak responses. The structure responses in little deformation, but it displaces at the end of excitation.

Key Words
sliding structure, sliding boundary problem, discontinuous deformation analysis

Address
Tsai JS, Natl Cheng Kung Univ, Dept Civil Engn, Tainan 70101, Taiwan
Natl Cheng Kung Univ, Dept Civil Engn, Tainan 70101, Taiwan

Abstract
Some design formulas and design procedures for single and multiple tuned liquid column dampers (TLCDs) are proposed in this study. Previous studies show that if the properties of the TLCD system are properly selected then the TLCD could be as effective as the traditional tuned mass dampers. In addition, the TLCD system offers advantages such as flexibility in terms of installation, little maintenance required, and potentials for multiple usage, etc., which are incomparable by other mechanical types of dampers. In this paper, a set of optimal properties such as length and head loss of a TLCD system are derived under the assumption that the building vibrates in a dominate mode and is subjected to Gaussian white noise excitation. A design procedure for a single TLCD system will be illustrated and discussed. Due to the nonlinearity in the damping term, the TLCD system is sensitive to the loading intensity. This loading sensitivity could limit the application range of the TLCD system. It will be shown in this paper that such a nonlinear effect can be reduced by using multiple TLCDs. As a demonstrative example, the control effects on a flexible building modeled as a single degree-of-freedom system subjected to white noise excitation will be analyzed and discussed using single or multiple TLCDs.

Key Words
control of buildings, TLCD, MTLCD, TMD, design procedure

Address
Chang CC, Hong Kong Univ Sci & Technol, Clear Water Bay, Kowloon, Hong Kong
Hong Kong Univ Sci & Technol, Kowloon, Hong Kong

Abstract
The extensive use of honeycomb sandwich structures has led to the need to understand and analyze their low velocity impact response. Commercially available finite element software provides a possible analysis tool for this type of problem, but the validity of their material properties models for honeycomb materials must be investigated. Three different problems that focus on the effect of differences in honeycomb material properties on static and dynamic response are presented and discussed. The first problem considered is a linear elastic static analysis of honeycomb sandwich beams. The second is a nonlinear elastic-plastic analysis of a circular honeycomb sandwich plate. The final problem is a dynamic analysis of circular honeycomb sandwich plates impacted by low velocity projectiles. Results are obtained using the ABAQUS final element code and compared against experimental results. The comparison indicates that currently available material properties models for honeycomb materials can be used to obtain a good approximation of the behavior of honeycomb sandwich structures under static and dynamic loading conditions.

Key Words
finite element analysis, honeycomb sandwich structures, low velocity impact, ABAQUS

Address
Triplett MH, Univ Alabama, Dept Civil & Environm Engn, Huntsville, AL 35899 USA
Univ Alabama, Dept Civil & Environm Engn, Huntsville, AL 35899 USA

Abstract
A novel boundary stress resolution method is suggested in this paper, which is based upon the displacements of finite element analysis and of high precision with stress boundary condition strictly satisfied. The method is used to modify the Zienkiewicz-Zhu (Z(2)) a posteriori error estimator and for the h-version adaptive finite element analysis of crack problems. Successful results are obtained.


Key Words
boundary stress resolution, Z(2) error estimator, h-version adaptive finite element analysis, crack problem

Address
Deng JH, Chinese Acad Sci, Inst Rock & Soil Mech, Wuhan, Peoples R China
Chinese Acad Sci, Inst Rock & Soil Mech, Wuhan, Peoples R China


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