Techno Press


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CONTENTS
Volume 14, Number 6, December 2002
 

Abstract
Parallel execution of computational mechanics codes requires efficient mesh-partitioning techniques. These mesh-partitioning techniques divide the mesh into specified number of submeshes of approximately the same size and at the same time, minimise the interface nodes of the submeshes. This paper describes a new mesh partitioning technique, employing Genetic Algorithms. The proposed
algorithm operates on the deduced graph (dual or nodal graph) of the given finite element mesh rather than directly on the mesh itself. The algorithm works by first constructing a coarse graph approximation using an automatic graph coarsening method. The coarse graph is partitioned and the results are interpolated onto the original graph to initialise an optimisation of the graph partition problem. In practice,
hierarchy of (usually more than two) graphs are used to obtain the final graph partition. The proposed partitioning algorithm is applied to graphs derived from unstructured finite element meshes describing practical engineering problems and also several example graphs related to finite element meshes given in the literature. The test results indicate that the proposed GA based graph partitioning algorithm generates high quality partitions and are superior to spectral and multilevel graph partitioning algorithms.

Key Words
load balancing; mesh partitioning; genetic algorithms; multilevel approaches; unstructured

Address
Structural Engineering Research Centre, CSIR Campus, Taramani, Chennai 600 113, India
Department of Aerospace Engineering, Indian Institute of Science, Bangalore 560 012, India

Abstract
Experimental results are presented from tests conducted on reinforced concrete beam-column joints with lap splices under reversed cyclic loading simulating earthquake action. Response curves are compared for twenty-four specimens designed according to Eurocode 2. The main parameters of the investigation are, the geometry of the reinforcing bar extension, the applied axial load (normalized), the available cover over lap splice region extended as length required from Eurocode 2, as well as the shape and the volumetric percentage of the stirrups confining the lap splice zone. The results are evaluated with regards to the load intensity, the energy absorption capacity and the charateristics of the load deflection curve.

Key Words
reinforced concrete; joints; beam-column connections; lap splices; bond; cyclic load; Euro-code 2.

Address
Department of Civil Engineering, Democritus University of Thrace, Xanthi 67 100, Greece

Abstract
The subject of this investigation is to study the buckling of cross-ply laminated orthotropic cylindrical thin shells with variable elasticity moduli and densities in the thickness direction, under external pressure, which is a power function of time. The dynamic stability and compatibility equations are obtained first. These equations are subsequently reduced to a system of time dependent differential
equations with variable coefficients by using Galerkin

Key Words
buckling; non-homogeneous; cross-ply laminated; orthotropic shell; external pressure; dynamic critical load; dynamic factor; critical impulse; wave number.

Address
Department of Civil Engineering, Suleyman Demirel University, Isparta, Turkey

Abstract
In this paper some techniques for the dynamic analysis of non-classically damped linear systems are reviewed and compared. All these methods are based on a transformation of the governing equations using a basis of complex or real vectors. Complex and real vector bases are presented and compared. The complex vector basis is represented by the eigenvectors of the complex eigenproblem obtained considering the non-classical damping matrix of the system. The real vector basis is a set of Ritz vectors derived either as the undamped normal modes of vibration of the system, or by the load dependent vector algorithm (Lanczos vectors). In this latter case the vector basis includes the static correction oncept. The rate of convergence of these bases, with reference to a parametric structural system subjected to a fixed spatial distribution of forces, is evaluated. To this aim two error norms are considered, the first based on the spatial distribution of the load and the second on the shear force at the base due to impulsive loading. It is shown that both error norms point out that the rate of convergence is strongly influenced by the spatial distribution of the applied forces.

Key Words
dynamic response; non-classical damping; Ritz method; Lanczos vectors; complex modal analysis.

Address
Dipartimento di Ingegneria Civile ed Ambientale, University of Catania, Viale Andrea Doria 6,
95125 Catania, Italy
Dipartimento di Meccanica e Materiali, University of Reggio Calabria, Feo di Vito,
89060 Reggio Calabria, Italy

Abstract
In this paper, a new quadrilateral 5-node non-conforming membrane element with drilling degrees of freedom is presented. The main advantage of these elements is the relatively small number of integration points to evaluate a stiffness matrix comparing to the existing transition membrane elements (CLM elements). Moreover, the presented elements pass the patch test by virtue of the Direct Modification Method incorporated into the element formulation. The presented 5-node elements are proved to be very efficient when used in the local mesh refinement for the in-plane structures which have stress concentrations. And some numerical studies also show the good performance of the new element developed in this study.

Key Words
membrane element; drilling degrees of freedom; irregular node; midside node.

Address
Department of Civil and Environmental Engineering, Korea Advanced Institute of Science and Technology, Daejeon 305-701, Korea

Abstract
A local radial point interpolation method (LRPIM) based on local residual formulation is presented and applied to solid mechanics in this paper. In LRPIM, the trial function is constructed by the radial point interpolation method (PIM) and establishes discrete equations through a local residual formulation, which can be carried out nodes by nodes. Therefore, element connectivity for trial function
and background mesh for integration is not necessary. Radial PIM is used for interpolation so that singularity in polynomial PIM may be avoided. Essential boundary conditions can be imposed by a straightforward and effective manner due to its Delta properties. Moreover, the approximation quality of the radial PIM is evaluated by the surface fitting of given functions. Numerical performance for this
LRPIM method is further studied through several numerical examples of solid mechanics.

Key Words
meshless method; radial basis function; point interpolation; background integration.

Address
Center for Advanced Computation in Engineering Science, Department of Mechanical and Production Engineering, National University of Singapore, 10 Kent Ridge Crescent, Singapore 119260

Abstract
A simplified rational method is developed to evaluate transverse earthquake-induced forces in continuous bridges. This method models the bridge as a beam on elastic foundation, and assumes a sinusoidal curve for both vibration mode shape and deflected shape in the transverse direction. The
principle of minimum total potential is used to calculate the displacements and the earthquake-induced forces in the transverse direction. This method is concise and easy to apply, and hence, offers an attractive alternative to a lengthy and time consuming three dimensional modeling of the bridge as given by AASHTO under its Single Mode Spectral Analysis Method.

Key Words
earthquake forces; bridge; transverse forces; seismic design; continuous bridge.

Address
Department of Civil Engineering, University of Jordan, P.O. Box 712506, Amman 11171, Jordan


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