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CONTENTS
Volume 4, Number 4, July 1996
 

Abstract
Presently welded components are designed using S/N curves which predict only the fatigue life of the component. In order to ascertain the condition of the weld at any intermediate period of its life inspection is carried out. If cracks are detected in a weld fracture mechanics is used to find their remaining life. A procedure for assessment is developed here that can be used to verify the condition of a weld before inspection is carried out to detect cracks. This simple method has been developed using linear,fracture envelopes by combining S/N curves with linear elastic fracture mechanics.

Key Words
assessment, bridges, fatigue, fracture mechanics, residual strength, welded component

Address
Ghosh A, UNIV ADELAIDE,DEPT CIVIL & ENVIRONM ENGN,ADELAIDE,SA 5005,AUSTRALIA
UNIV ADELAIDE,DEPT MECH ENGN,ADELAIDE,SA 5005,AUSTRALIA

Abstract
Stability equations that evaluate the elastic critical axial load of columns in any type of construction with sidesway uninhibited, partially inhibited, and totally inhibited are derived in a classical manner. These equations can be applied to the stability of frames (unbraced, partially braced, and totally braced) with rigid, semirigid, and simple connections. The complete column classification and the corresponding three stability equations overcome the limitations and paradoxes of the well known alignment charts for braced and unbraced columns and frames. Simple criteria are presented that define the concept of partially braced columns and frames, as well as the minimum lateral bracing required by columns and frames to achieve non-sway buckling mode. Various examples are presented in detail that demonstrate the effectiveness and accuracy of the complete set of stability equations.

Key Words
buckling, building codes, construction type, columns, computer applications, design, frames, loads, stability

Address
AristizabalOchoa JD, NATL UNIV,SCH MINES,MEDELLIN,COLOMBIA

Abstract
In this paper, the behavior of plates partially restrained against rotation under stress gradient is investigated. As a first stage, an energy formulation is presented to model this boundary condition and a general expression is derived for the prediction of the elastic buckling of the plate under this general loading condition. The accuracy of the derived expression is compared numerically using the Galerkin method with other available data for the two limiting conditions of rotationally free and clamped boundaries. Results show that the prediction is within a 5% difference.

Key Words
plate buckling, stiffened plate, plates under compression and bending, plates partially restrained against rotation, plate modelling using the energy method

Address
Bedair OK, CONCORDIA UNIV,DEPT CIVIL ENGN,1455 MAISONNEUVE BLVD W,MONTREAL,PQ H3G 1M8,CANADA

Abstract
In this paper the elastic post-buckling behaviour of plates under non-uniform compressive edge stress is investigated. The compatibility differential equations is first solved analytically and then an approximate solution of the equilibrium equation is obtained using the Galerkin method. Explicit expressions are derived for the load-deflection, ultimate strength and membrane stress distributions. Analytical effective width formulations, based on the characteristics of the stress field of the buckled plate, are proposed for this general loading condition. The predicted load-deflection expression is compared with independent test results. Results are also presented detailing the load-deflection behaviour and stress distribution for various aspect ratios.

Key Words
plate post-buckling, stiffened plate, effective width, ultimate strength of plates, non-linear analysis of plates

Address
Bedair OK, CONCORDIA UNIV,DEPT CIVIL ENGN,1455 MAISONNEUVE BLVD W,MONTREAL,PQ H3G 1M8,CANADA

Abstract
This paper presents a newly suggested calculation method in which an arbitrary quadrilateral element with curved sides is transformed to a normal rectangular one by mapping of coordinates, then the two-dimensional spline is adopted to approach the displacement function of this element. Finally the solution can be obtained by the least-energy principle. Thereby, the application field of Spline Finite Element Method will be extended.

Key Words
mapping, spline function, finite element method, curved plate, skew plate, arbitrary quadrilateral plate, curved sides, displacement function, bending

Address
Ding HS, NANJING INST TECHNOL,NANJING 210018,PEOPLES R CHINA

Abstract
An application of the perturbation method to optimum structural design with random parameters is presented. It is formulated on the basis of the first-order stochastic finite element perturbation method. It also takes into full account the stress, displacement and eigenvalue constraints, together with the rates of change of the random variables. A method for calculating the sensitivity coefficients in regard to the governing equation and the first-order perturbed equation has been derived, by using a direct differentiation approach. A gradient-based nonlinear programming technique is used to solve the problem. The numerical results are specifically noted, where the stiffness parameter and external load are treated as random variables.

Key Words
stochastic finite element method, first-order perturbation, optimal design, sensitivity analysis

Address
Lee BW, DONGEUI TECH JR COLL,PUSANJIN KU,72 YANGJEONG DONG,PUSAN,SOUTH KOREA
PUSAN NATL UNIV,RES INST MECH TECHNOL,PUSAN 609735,SOUTH KOREA

Abstract
A study on the behaviour of fibre reinforced concrete deep beams with and without web openings is carried out using nonlinear finite element analysis. Eight node isoparametric plane stress elements are employed to model the fibre reinforced concrete materials. Steel bars are treated using a compatible three node truss elements. The constitutive equations for fibre reinforced concrete materials take into account the softening effect of co-existing shear strains. Element stiffness at each step is formulated based on the tangent modulus at the current level of principal strains. Transformation between principal directions and global coordinate system is imposed. Comparison of analytical results with experimental values indicates reasonably good agreement, The proposed numerical model can be used to study the behaviour of this composite structures of practically any geometries.

Key Words
deep beams, fibre reinforced concrete, finite element, material nonlinearity, web openings

Address
Swaddiwudhipong S, NATL UNIV SINGAPORE,DEPT CIVIL ENGN,10 KENT RIDGE CRESCENT,SINGAPORE 0511,SINGAPORE

Abstract
We propose a new shape of cylindrical shell formed by multiples vaults which gives a self-stiffening against buckling. By an experimental and numerical study of cylindrical shells with a repeated defect, on the circumferential direction made only of outside oriented wave-defects, we show that multiple vault cylindrical shells can have a good behaviour in buckling. An optimal behaviour is obtained by optimization of the vaults number, with conduces to a special multiple vault cylindrical shell named \'\'ASTER shell\'\'.

Key Words
cylindrical shell, external pressure, buckling, self-stiffening, boundary conditions, geometric imperfection

Address
Araar M, UNIV ANNABA,INST CIVIL ENGN,BP 12,ANNABA,ALGERIA
INSA,CONCRETE & STRUCT LAB,F-69621 VILLEURBANNE,FRANCE

Abstract
none

Key Words
none

Address
Laura PAA, UNIV NACL SUR,DEPT ENGN,INST APPL MECH,CONICET,RA-8000 BAHIA BLANCA,ARGENTINA

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