Techno Press
Tp_Editing System.E (TES.E)
Login Search


sem
 
CONTENTS
Volume 24, Number 2, September30 2006
 

Abstract
The reliable pushover analysis of RC structures requires a realistic prediction of moment-curvature relations, which can be obtained by utilizing proper constitutive models for the stress-strain relationships of laterally confined concrete members. Theoretical approach of Mander is still a single stress-strain model, which employs a multiaxial failure surface for the determination of the ultimate strength of confined concrete. Alternatively, this paper introduces a simple and practical failure criterion for confined concrete with emphasis on introduction of significant modifications into the two-parameter Drucker-Prager model. The new criterion is only applicable to triaxial compression stress state which is exactly the case in the RC columns. Unlike many existing multi-parameter criteria proposed for the concrete fracture, the model needs only the compressive strength of concrete as an independent parameter and also implies for the influence of the Lode angle on the material strength. Adopting Saenz equation for stress-strain plots, satisfactory agreement between the measured and predicted results for the available experimental test data of confined normal and high strength concrete specimens is obtained. Moreover, it is found that further work involving the confinement pressure is still encouraging since the confinement model of Mander overestimates the ultimate strength of some RC columns.

Key Words
failure criterion; compressive strength; concrete; column; stress-strain relation

Address
Faculty of Civil Engineering, Yildiz Technical University, 34349 Be ikta /Istanbul, Turkey

Abstract
Many applications in mechanical design involve elastic bodies coming into contact under the action of the applied load. The distribution of the contact pressure throughout the contact interface plays an important role in the performance of the contact system. In many applications, it is desirable to minimize the maximum contact pressure or to have an approximately uniform contact pressure distribution. Such requirements can be attained through a proper design of the initial surfaces of the contacting bodies. This problem involves a combination of two disciplines, contact mechanics and shape optimization. Therefore, the objective of the present paper is to develop an integrated procedure capable of evaluating the optimal shape of contacting bodies. The adaptive incremental convex programming method is adopted to solve the contact problem, while the augmented Lagrange multiplier method is used to control the shape optimization procedure. Further, to accommodate the manufacturing requirements, surface parameterization is considered. The proposed procedure is applied to a couple of problems, with different geometry and boundary conditions, to demonstrate the efficiency and versatility of the proposed procedure.

Key Words
contact mechanics; shape optimization; mathematical programming; surface parameterization; finite element method.

Address
Department of Mechanical Engineering, Zagazig University, Zagazig, 44511, Egypt

Abstract
The masonry is a complex heterogeneous material and its shear deformation and fracture is associated with very complicated progressive failures in masonry structure, and is investigated in this paper using a mesoscopic mechanical modelling, Considering the heterogeneity of masonry material, based on the damage mechanics and elastic-brittle theory, the newly developed Material Failure Process Analysis (MFPA) system was brought out to simulate the cracking process of masonry, which was considered as a three-phase composite of the block phase, the mortar phase and the block-mortar interfaces. The crack propagation processes simulated with this model shows good agreement with those of experimental observations by other researchers. This finding indicates that the shear fracture of masonry observed at the macroscopic level is predominantly caused by tensile damage at the mesoscopic level. Some brittle materials are so weak in tension relative to shear that tensile rather than shear fractures are generated in pure shear loading.

Key Words
meso-scopic damage model; elastic damage mechanics; fracture process; masonry

Address
Shuhong Wang; School of Resource and Civil Engineering, Northeastern University, Shenyang, 110004, P. R. China
Chun?n Tang; Lab for Numerical Test on Material Failure, Dalian University, Dalian, 116024, P. R. China
Peng Jia; School of Resource and Civil Engineering, Northeastern University, Shenyang, 110004, P. R. China

Abstract
In seismic areas, ductility is an important factor in design of high strength concrete (HSC) members under flexure. A number of twelve HSC beams with different percentage of r & r \' were cast and incrementally loaded under bending. The effect of r\' on ductility of members were investigated both qualitatively and quantitatively. During the test, the strain on the concrete middle faces, on the tension and compression bars, and also the deflection at different points of the span length were measured up to failure. Based on the obtained results, the serviceability and ultimate behavior, and especially the ductility of the HSC members are more deeply reviewed. Also a comparison between theoretical and experimental results are reported here.

Key Words
curvature and displacement ductility; HSC members; serviceability.

Address
Civil Engineering Department, Kerman University, Kerman, Iran

Abstract
The propagation of non-uniformly modulated, evolutionary random waves in viscoelastic, transversely isotropic, stratified materials is investigated. The theory is developed in the context of a multi-layered soil medium overlying bedrock, where the material properties of the bedrock are considered to be much stiffer than those of the soil and the power spectral density of the random excitation is assumed to be known at the bedrock. The governing differential equations are first derived in the frequency/wave-number domain so that the displacement response of the ground may be computed. The eigen-solution expansion method is then used to solve for the responses of the layers. This utilizes the precise integration method, in combination with the extended Wittrick-Williams algorithm, to obtain all the eigen-solutions of the ordinary differential equation. The recently developed pseudo-excitation method for structural random vibration is then used to determine the solution of the layered soil responses.

Key Words
layered material; precise integration; pseudo-excitation method; extended Wittrick-Williams algorithm; wave propagation; random vibration

Address
Q. Gao; Key Laboratory of Structural Analysis for Industrial Equipment, Dalian University of Technology, Dalian, 116023, China
W. P. Howson; Cardiff School of Engineering, Cardiff University, The Parade, Cardiff CF24 3AA, UK
A. Watson; Department of Aeronautical and Automotive Engineering, Loughborough University, Loughborough, LE11 3TU, UK
J. H. Lin; Key Laboratory of Structural Analysis for Industrial Equipment, Dalian University of Technology, Dalian, 116023, China

Abstract
The performance of a three dimensional non-linear finite element model for hyperelastic material considering the effect of compressibility is studied by analyzing rubber blocks under different modes of deformation. It includes simple tension, pure shear, simple shear, pure bending and a mixed mode combining compression, shear and bending. The compressibility of the hyperelastic material is represented in the strain energy function. The nonlinear formulation is based on updated Lagrangian (UL) technique. The displacement model is implemented with a twenty node brick element having u, v and w as the degrees of freedom at each node. The results obtained by the present numerical model are compared with the analytical solutions available for the basic modes of deformation where the agreement between the results is found to be satisfactory. In this context some new results are generated for future references since the number of available results on the present problem is not sufficient enough.

Key Words
nonlinear finite element model; compressible strain energy function; hyperelastic material.

Address
M. C. Manna and A. H. Sheikh; Department of Ocean Engineering and Naval Architecture, Indian Institute of Technology, Kharagpur – 721 302, India
R. Bhattacharyya; Department of Mechanical Engineering, Indian Institute of Technology, Kharagpur – 721 302, India

Abstract
The parts of pile, above the soil and embedded in the soil are called the first region and second region, respectively. The forth order differential equations of both region for critical buckling load of partially embedded pile with shear deformation are obtained using the small-displacement theory and Winkler hypothesis. It is assumed that the behavior of material of the pile is linear-elastic and that axial force along the pile length and modulus of subgrade reaction for the second region to be constant. Shear effect is included in the differential equations by considering shear deformation in the second derivative of the elastic curve function. Critical buckling loads of the pile are calculated for by differential transform method (DTM) and analytical method, results are given in tables and variation of critical buckling loads corresponding to relative stiffness of the pile are presented in graphs.

Key Words
static stability; differential transform method; critical buckling load; partially embedded pile; non-trivial solution.

Address
Dokuz EylŸl University, Civil Engineering Department, Engineering Faculty, 35160, Buca, ezmir, Turkey

Abstract
In this study, the finite element linear buckling analysis of folded plate structures using adaptive h-refinement methods is presented. The variable-node flat shell element used in this study possesses a drilling D.O.F. which, in addition to improvement of the element behavior, permits an easy connection to other elements with six degrees of freedom per node (CLS element, Choi and Lee 1996). Accordingly, the folded plate structures, for which it is hard to find the analytical solutions, can be analyzed with a relative ease using the developed flat shell elements. Using the adaptive h-refinement procedure, the convergent buckling modes and the critical loads of these modes can be obtained by the buckling analyses of those structures.

Key Words
CLS element; drilling D.O.F.; folded plate structures; finite element buckling analysis; adaptive h-refinement; super-convergent patch recovery; critical loads; buckling modes

Address
Myung-Kwan Song; R & D Department, Structural Division, Yooshin Engineering Corporation, Seoul 135-936, Korea Republic
Kyeong-Ho Kim; Department of Specific Structures, Chungsuk Engineering CO., LTD., Seoul 138-802, Korea Republic
Sun-Hoon Kim; Department of Civil Engineering, Youngdong University, Chungbuk 370-701, Korea Republic


Techno-Press: Publishers of international journals and conference proceedings.       Copyright © 2017 Techno-Press
P.O. Box 33, Yuseong, Daejeon 34186 Korea, Tel: +82-42-828-7996, Fax : +82-42-828-7997, Email: info@techno-press.com