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CONTENTS
Volume 5, Number 1, January 1997
 

Abstract
A numerical procedure for dynamic analysis of structures including lateral-torsional coupling, axial force effect and soil-structure interaction is presented in this study. A simple soil-structure system model has been designed for microcomputer applications capable of reflecting both kinematic and inertial soil-foundation interaction as well as the effect of this interaction on the superstructure response. A parametric study focusing on inertial soil-structure interaction is carried out through a simplified nine-degree of freedom building model with different foundation conditions. The inertial soil-structure interaction and axial force effects on a 20-storey building excited by an Australian earthquake is analysed through its top floor displacement time history and envelope values of structural maximum displacement and shear force.

Key Words
soil-structure interaction, kinematic soil-structure interaction, inertial soil-structure interaction, multistorey building, axial force effect, geometric non-linear stiffness

Address
Gao H, UNIV SYDNEY,SCH CIVIL & MIN ENGN,SYDNEY,NSW 2006,AUSTRALIA
UNIV TECHNOL SYDNEY,GRAD SCH ENGN,SYDNEY,NSW 2007,AUSTRALIA

Abstract
A new torsional analysis method for multiple cell box based on the Softened Truss Model Theory was developed. This softened truss model unifies shear and torsion to address the problem associated with a torque applied on a box. The model should be very useful for the analysis of a reinforced concrete box under torque, especially for the bridge superstructure with multiple cell box sections.

Key Words
bridge analysis, torsion, softened truss model, multiple cell, box, reinforced concrete

Address
UNIV MARYLAND,DEPT CIVIL ENGN,COLLEGE PK,MD 20742

Abstract
A method of analysis is proposed for curved multicell box girder grillages. The method can be used to analyze box girder grillages comprising straight and/or curved segments. Each segment can be modelled by a number of beam elements. Each element has three nodes and the nodal degrees of freedom (DOF) consist of the six DOF for a conventional beam plus DOF to account for torsional warping, distortion,distortional warping, and shear lag. This element is an extension of a straight element that was developed earlier. For a more realistic analysis of the intersection regions of non-colinear box girder segments, the concept of a rigid connector is introduced, and the compatibility requirements between adjoining elements in those regions are discussed. The results of the analysis showed good agreement with the shell finite element results, but the proposed method of analysis needs a fraction of the time and effort compared to the shell finite element analysis.

Key Words
analysis, beam, box girder, bridge, finite element, structures, thin-walled

Address
Razaqpur AG, CARLETON UNIV,DEPT CIVIL & ENVIRONM ENGN,1125 COLONEL DR,OTTAWA,ON R1S 586,CANADA

Abstract
The influence of bi-directional earthquake-induced loading on eccentric (plan-asymmetric) building systems has been investigated. In the first part of the study, comparisons have been made with equivalent results from uni-directional studies. The results are important in developing analytical models appropriate to the formulation of design recommendations. It is concluded that for valid comparisons, both perpendicular horizontal earthquake components must be considered when using models with transversely-orientated elements. In the second part of the study, an assessment has been made of a simplified, uni-directional (lateral) design approach. For stiffness-eccentric systems, the latter approach gives accurate and reasonably conservative estimates of the critical flexible-edge deformation, but may under estimate the stiff-edge element ductility demand by a factor of two in the short-period range.

Key Words
eccentric systems, inelastic torsional effects, bi-directional loading

Address
Chandler AM, UNIV COLL LONDON,DEPT CIVIL & ENVIRONM ENGN,GOWER ST,LONDON WC1E 6BT,ENGLAND
UNIV MELBOURNE,DEPT CIVIL & ENVIRONM ENGN,PARKVILLE,VIC 3052,AUSTRALIA

Abstract
A two-step method is presented for the optimum design of trusses with available sections under stress and Euler buckling constraints. The shape design of the truss is used as a means to convert the discrete solution into a continuous one. In the first step of the method, a continuous solution is obtained by sizing and shape design using an approximate polynomial expression for the buckling coefficients. In the second step, the member sizes obtained are changed to the nearest available sections and the truss is reconfigured by using the exact values for the buckling coefficients. The optimizer used is based on the sequential quadratic programming and the gradients are evaluated in closed form. The method is illustrated by two numerical examples.


Key Words
truss, sizing, shape design, optimization, available sections, sensitivity analysis

Address
Oral S, MIDDLE E TECH UNIV,DEPT MECH ENGN,TR-06531 ANKARA,TURKEY
ARCELIK AS,ANKARA,TURKEY

Abstract
A new efficient hybrid/mixed thin similar to moderately thick plate bending element with B-node (HM6-14) is formulated based on the Reissner-Mindlin plate bending theory. The convergence of this element is proved by error estimate theories and verified by patch test respectively. Numerical studies on such an element as HM6-14 demonstrate that it has remarkable convergence, invariability to geometric distorted mesh situations, to axial rotations, and to node positions, and no \'\'locking\'\' phenomenon in thin plate limit. The present element is suitable to many kinds of shape and thin similar to moderately thick plate bending problems. Further, in comparison with original hybrid/mixed plate bending element HP4, the present element yields an improvement of solutions. Therefore, it is an efficient element and suitable for the development of adaptive multi-field finite element method (FEM).

Key Words
hybrid/mixed FEM, Mindlin/Reissner plate theory

Address
Mei D, IWATE UNIV,FAC CIVIL ENGN,MORIOKA,IWATE 020,JAPAN
SW JIAOTONG UNIV,INST COMPUTAT ENGN SCI,CHENGDU,PEOPLES R CHINA

Abstract
The paper investigates the influence of lateral restraint on the buckling behaviour of plate under non-uniform compression. The unloaded edges are assumed to be partially restrained against translation in the plane of the plate and the distributions of the resulting forces acting on the plate are shown. The stability analysis is done numerically using the Galerkin method and various strategies the economize the numerical implementation are presented. Results are obtained showing the variation of the buckling load, from free edge translation to fully restrained, with unloaded edges simply supported, clamped and partially restrained against rotation for various plate aspect ratios and stress gradient coefficients. An apparent decrease in the buckling load is observed due to these destabilizing forces acting in the plate and changes in the buckling modes are observed by increasing the intensity of the lateral restraint. A comparison is made between the budding loads predicted from various formulas in stability standards based on free edge translation and the values derived from the present investigation. A difference of about 34% in the predicted buckling load and different buckling mode were found.

Key Words
plate buckling, lateral restrain, Galerkin method

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

Abstract
This paper proposes a model for simulating concrete shrinkage taking into account aggregate restraint. In the model, concrete is regarded as a two-phase material based on shrinkage property. One is paste phase which undergoes shrinkage. Another is aggregate phase which is much more volumetrically stable. In the concrete, the aggregate phase is considered to restrain the paste shrinkage by particle interaction. Strain compatibility was derived under the assumption that there is no relative macroscopic displacement between both phases. Stresses on both phases were derived based on the shrinking stress of the paste phase and the resisting stress of the aggregate phase. Constitutive relation of paste phase was adopted from the study of Yomeyama, K. pr al, and that of the aggregate phase was adopted from the author\'s particle contact density model. The equation for calculating concrete shrinkage considering aggregate restraint was derived from the equilibrium of the two phases. The concrete shrinkage was found to be affected by the free shrinkage of the paste phase, aggregate content and the stiffness of both phases. The model was then verified to be effective for simulating concrete shrinkage by comparing the predicted results with the autogeneous and drying shrinkage test results on mortar and concrete specimens.

Key Words
modeling, concrete, shrinkage, aggregate restraint, multi-phase material

Address
Tangtermsirikul S, THAMMASAT UNIV,SIRINDHORN INT INST TECHNOL,DEPT CIVIL ENGN,PATHUM THANI 12121,THAILAND
ASIAN INST TECHNOL,SCH CIVIL ENGN,PATHUM THANI 12121,THAILAND


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