Techno Press


sem
 
CONTENTS
Volume 3, Number 4, July 1995
 

Abstract
A new reinforcing steel model which is embedded inside a concrete element and also accounts for the effect of bond-slip is developed. Unlike the classical bond-link or bond-zone element using double nodes, the proposed model is considering the bond-slip effect without taking double nodes by incorporation of the equivalent steel stiffness. After calculation of nodal displacements, the deformation of steel at each node can be found through the back-substitution technique from the first to the final steel element using a governing equation constructed based on the equilibrium at each node of steel and the compatibility condition between steel and concrete. This model results in significant savings in the number of nodes needed to account for the effect of bond-slip, in particular, when the-model is used for three dimensional finite element problems. Moreover a new nonlinear solution scheme is developed in connection with this model. Finally, correlation studies between analytical and experimental results and several parameter studies are conducted with the objective to establish the validity of the proposed model.


Key Words
BOND-SLIP, STEEL MODEL, DOUBLE NODE, SOLUTION ALGORITHM, EQUILIBRIUM

Address
KWAK HG, SAMSUNG ENGN & CONSTRUCT CO,KANGNAM POB 1430,SEOUL 135080,SOUTH KOREA
UNIV CALIF BERKELEY,DEPT CIVIL ENGN,BERKELEY,CA 94720

Abstract
Flexible cantilever pipes conveying fluids with high velocity are analysed for their dynamic response and stability behaviour. The Young\'s modulus and mass per unit length of the pipe material have a stochastic distribution. The stochastic fields, that model the fluctuations of Young\'s modulus and mass density are characterized through their respective means, variances and autocorrelation functions or their equivalent power spectral density functions. The stochastic non self-adjoint partial differential equation is solved for the moments of characteristic values, by treating the point fluctuations to be stochastic perturbations. The second-order statistics of vibration frequencies and mode shapes are obtained. The critical flow velocity is-first evaluated using the averaged eigenvalue equation. Through the eigenvalue equation, the statistics of vibration frequencies are transformed to yield critical flow velocity statistics. Expressions for the bounds of eigenvalues are obtained, which in turn yield the corresponding bounds for critical flow velocities.

Key Words
FLUID PIPES, STOCHASTIC, DYNAMICS, STABILITY

Address
GANESAN R, CONCORDIA UNIV,DEPT MECH ENGN,MONTREAL,PQ H3G 1M8,CANADA
INDIAN INST SCI,DEPT CIVIL ENGN,BANGALORE 560012,KARNATAKA,INDIA

Abstract
The iterative procedure to use the nonconforming elements in elasto-plastic problems is established and applied to the variable node transition solid element developed for the automated three-dimensional local mesh refinement. Through numerical tests, the validity and performance of the element are examined. As the nonlinear iterative procedure presented in this paper is accomplished for the general three-dimensional case, it can also be easily applied to the two-dimensional elements such as membranes, plates and shells.

Key Words
ELASTOPLASTIC ANALYSIS, MESH REFINEMENT, NONCONFORMING MODES, STEEP STRESS GRADIENT, SUPER-CONVERGENT PATCH RECOVERY, TRANSITION SOLID ELEMENT, VARIABLE NODE, YIELD PROPAGATION

Address
CHOI CK, KOREA ADV INST SCI & TECHNOL,DEPT CIVIL ENGN,TAEJON,SOUTH KOREA

Abstract
The results of a series of ten W-shaped test specimens subjected to monotonic, quasi-static cyclic loading and fatigue type of loading in the form of constant amplitude tests are presented. The objectives were to assess and compare the rotation capacity and energy absorption of monotonically and cyclically loaded beams, and for the latter specimens to document the deterioration in the form of low cycle fatigue due to local buckling. In addition, strength and energy dissipation deterioration and damage models have been developed for the steel beam section under consideration. Finally, a generalized model which uses plate slenderness values and lateral slenderness is proposed for predicting rate in strength deterioration per reversal and cumulated damage after a given number of reversals.

Key Words
DAMAGE, STEEL STRUCTURES, CYCLIC, FATIGUE, DETERIORATION, STRENGTH, ENERGY, LOCAL BUCKLING

Address
DAALI ML, HATCH ASSOCIATES LTD,SUDBURY,ON P3C 1X3,CANADA
MCMASTER UNIV,DEPT CIVIL ENGN & ENGN MECH,HAMILTON,ON L8S 4L7,CANADA

Abstract
This study presents an efficient method for optimum design of plate and shell structures, when the design variables are continuous or discrete. Both sizing and shape design variables are considered. First the structural responses such as element forces are approximated in terms of some intermediate variables. By substituting these approximate relations into the original design problem, an explicit nonlinear approximate design task with high quality approximation is achieved. This problem with continuous variables, can be solved by means of numerical optimization techniques very efficiently, the results of which are then used for discrete variable optimization. Now, the approximate problem is converted into a sequence of second level approximation problems of separable form and each of which is solved by a dual strategy with discrete design variables. The approach is efficient in terms of the number of required structural analyses, as well as the overall computational cost of optimization. Examples are offered and compared with other methods to demonstrate the features of the proposed method.

Key Words
APPROXIMATION, CONTINUOUS VARIABLE, DISCRETE VARIABLE, OPTIMIZATION, PLATE AND SHELL, DUAL METHOD

Address
SALAJEGHEH E, UNIV KEMAN,DEPT CIVIL ENGN,KEMAN,IRAN

Abstract
The weighting strategy has received a great attention and has been widely applied to multicriterion optimization. This gaper examines a global criterion method (GCM) with the weighting objectives strategy in fuzzy structural engineering problems. Fuzziness of those problems are in their design goals, constraints and variables. Most of the constraints are originated from analysis of engineering mechanics. The GCM is verified to be equivalent to fuzzy goal programming via a truss design. Continued and mixed discrete variable spaces are presented and examined using a fuzzy global criterion method (FGCM). In the design process a weighting parameter with fuzzy information is introduced into the design and decision making. We use a uniform machine-tool spindle as an illustrative example in continuous design space. Fuzzy multicriterion Optimization in mixed design space is illustrated by the design of mechanical spring stacks. Results show that weighting strategy in FGCM can generate both the best compromise solution and a set of Pareto solutions in fuzzy environment. Weighting technique with fuzziness provides a more relaxed design domain, which increases the satisfying degree of a compromise solution or improves the final design.


Key Words
WEIGHTING OBJECTIVES STRATEGY, MULTICRITERION FUZZY OPTIMIZATION, FUZZY GOAL PROGRAMMING, FUZZY GLOBAL CRITERION METHOD, FUZZY WEIGHTING TECHNIQUE, CONTINUOUS DESIGN SPACE, MIXED-DISCRETE DESIGN SPACE, TRUSS, MACHINE-TOOL SPINDLE, MECHANICAL SPRING

Address
SHIH CJ, TAMKANG UNIV,DEPT MECH ENGN,TAMSUI 25137,TAIWAN
YEU TYAN MACHINERY MFG CO,CTR VEHICLE DESIGN & DEV,CHANGHUA 51500,TAIWAN

Abstract
A 2-D four-noded finite element which contains a lambda singularity is developed. The new element is compatible with quadratic standard isoparametric elements. The element is tested on two different examples. In the first example, an edge crack problem is analyzed using two different meshes and different integration orders. The second example is a crack perpendicular to the interface problem which is solved for different material properties and in turn different singularity order lambda. The results of those examples illustrate the efficiency of the proposed element.

Key Words
FRACTURE MECHANICS, FINITE ELEMENT METHOD

Address
WAHAB MMA, KATHOLIEKE UNIV LEUVEN,DEPT CIVIL ENGN,B-3001 LOUVAIN,BELGIUM

Abstract
The application of adaptive finite element method to dynamic problems is investigated. Both the kinetic and strain energy errors induced by space and time discretization were estimated in a consistent manner and controlled by the simultaneous use of the adaptive mesh generation and the automatic time stepping. Also an optimal ratio of spatial discretization error to temporal discretization error was discussed. In this study it was found that the best performance can be obtained when the specified spatial and temporal discretization errors have the same value. Numerical examples are carried out to verify the performance of the procedure.

Key Words
ADAPTIVE ANALYSIS, DYNAMIC ANALYSIS, STRESS WAVE PROPAGATION, DISCRETIZATION ERROR, FINITE ELEMENT ANALYSIS, DIRECT TIME INTEGRATION, NEWMARK METHOD

Address
CHOI CK, KOREA ADV INST SCI & TECHNOL,DEPT CIVIL ENGN,TAEJON 305701,SOUTH KOREA


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