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CONTENTS
Volume 8, Number 4, October 1999
 

Abstract
A procedure for the computation of the load carrying capacity of perfectly plastic plates in bending is presented. The approach, based on the kinematic theorem of limit analysis, requires the evaluation of the minimum of a convex, but non-smooth, function under linear equality constraints. A systematic solution procedure is devised, which detects and eliminates the finite elements which are predicted as rigid in the collapse mechanism, thus reducing the problem to the search for the minimum of a smooth and essentially unconstrained function of nodal velocities. Both Kirchhoff and Mindlin plate models are considered. The effectiveness of the approach is illustrated by means of some examples.

Key Words
rigid-plastic material, limit analysis, plates

Address
Capsoni A, Politecn Milan, Dept Struct Engn, Piazza Leonardo Vinci 32, I-20133 Milan, Italy
Politecn Milan, Dept Struct Engn, I-20133 Milan, Italy

Abstract
This work applies a structural analysis method based on an analytical solution from the Fourier series which transforms a half-range cosine expansion into a static solution involving plated structures. Two sub-matrices of in-plane and plate-bending problems are also formulated and coupled with the prescribed boundary conditions for these variables, thereby providing a convenient basis for a numerical solution. In addition, the plate connection are introduced by describing the connection between common boundary continuity and equilibrium. Moreover, a simple computation scheme is proposed. Numerical results are then compared with finite element results, demonstrating the numerical scheme\'s versatility and accuracy.

Key Words
Fourier series, half-range cosine expansion, in-plane stress, plate-bending stress, plated structures

Address
Deng JG, Natl Chiao Tung Univ, Dept Civil Engn, 1001 Ta Hseuh Rd, Hsinchu, Taiwan
Natl Chiao Tung Univ, Dept Civil Engn, Hsinchu, Taiwan

Abstract
This paper reviews aspects of current design procedures for seismic design of structures, and specifically examines their relevance to the design of light framed residential buildings under earthquake loading. The significance of the various structural contributions made by the components of cold formed steel framed residential structures subjected to earthquake induced loadings has been investigated. This is a common form of residential construction worldwide. Particular attention is given to aspects related to ductility and overstrength, the latter arising principally from the contributions of the designated \"non-stntctural\" components. Based on both analytical and experimental data obtained from research investigations on steel framed residential structures, typical ranges of the ductility reduction factor and overstrength ratios are determined. It is concluded that the latter parameter has a very significant influence on the seismic design of such structures. Although the numerical ranges for the inelastic seismic parameters given in this paper were obtained for Australian houses, the concepts and the highlighted aspects of seismic design methodology are more widely applicable.

Key Words
light framed structures, houses, ductility, overstrength, seismic design

Address
Univ Hong Kong, Dept Civil & Struct Engn, Hong Kong, Hong Kong
Univ Melbourne, Dept Civil & Environm Engn, Parkville, Vic 3052, Australia

Abstract
in some space truss applications, particularly those with large spans, the choice of a triple-layer system might prove more cast effective than the more commonly used double-layer solution. However, there are currently no clear guidelines as to which system would be more competitive for intermediate span lengths. in this paper, comparisons in terms of the weight, stiffness and number of joints and members are made between the two system types and presented in order to simplify the choice process for the designer. The comparisons are carried out using an approximate analysis technique that is explained in this paper, and checked to be reasonably accurate and suitable for the preliminary design of space trusses.

Key Words
space trusses, approximate analysis, design, competitiveness

Address
El-Sheikh A, Univ Dundee, Dept Civil Engn, Dundee DD1 4HN, Scotland
Univ Dundee, Dept Civil Engn, Dundee DD1 4HN, Scotland

Abstract
A method of optimum design based on reliability for antenna structures is presented in this paper. By constructing the equivalent event, the formula is derived for calculating the reliability of reflector accuracy of antenna under the action of random wind load. The optimal model is developed, in which the cross sectional areas of member are treated as design variables, the structure weight as objective function, the reliability of reflector accuracy and the strength or stability of structural elements as constraints. The improved accelerated convergence gradient algorithm developed by the author is used. The design results show that the method in this paper is feasible and effective.

Key Words
antenna structure, reflector accuracy, strength and stability, reliability constraints, optimum design, improved accelerated convergence gradient algorithm

Address
Chen JJ, Xidian Univ, Dept Elect Mech Engn, Xian 710071, Peoples R China
Xidian Univ, Dept Elect Mech Engn, Xian 710071, Peoples R China

Abstract
A nonlinear model for time-step analysis of bridges subjected to two orthogonal horizontal components of earthquake motions was developed. The focus of the study was on elastomeric isolators with or without lead cores. The hysteretic behavior of the isolators, the columns, abutments, and shear keys was taken into account. The nonlinear analysis showed that, contrary to linear theory prediction, the use of isolators does not necessarily increase the displacement of the superstructure. Furthermore, it was shown that properly designed isolators can reduce the ductility demand in RC bridge columns substantially.

Key Words
abutments, base isolation, bridges, columns, displacement, earthquakes, elastomeric, force, seismic

Address
Saiidi M, Univ Nevada, Dept Civil Engn, Reno, NV 89557 USA
Univ Nevada, Dept Civil Engn, Reno, NV 89557 USA
Exeltech Engn, Olympia, WA 98502 USA

Abstract
In this paper a practical limit load estimating procedure is proposed for general pipe-elbow structures subjected to complex loading (in-plane and out-of-plane bending, internal pressure and axial force). The explicit calculating formulae are presented on the basis of theoretical analysis combined with numerical simulation. Von Mises\' yield criterion is adopted in both analytical and numerical calculation. The finite element examination shows that the method provides a simple but satisfactory prediction of pipe structures in engineering plastic analysis.

Key Words
limit analysis, limit load, bending of curved pipe, pipe structures, elbow

Address
Yan AM, Univ Liege, LTAS, Rue Ernest Solvay 21, B-4000 Liege, Belgium
Univ Liege, LTAS, B-4000 Liege, Belgium
Framatome, Paris, France


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