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REFERENCE LINKING PLATFORM OF KOREA S&T JOURNALS
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Structural Engineering and Mechanics
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Volume 12, Issue 6 - Dec 2001
Volume 12, Issue 5 - Nov 2001
Volume 12, Issue 4 - Oct 2001
Volume 12, Issue 3 - Sep 2001
Volume 12, Issue 2 - Aug 2001
Volume 12, Issue 1 - Jul 2001
Volume 11, Issue 6 - Jun 2001
Volume 11, Issue 5 - May 2001
Volume 11, Issue 4 - Apr 2001
Volume 11, Issue 3 - Mar 2001
Volume 11, Issue 2 - Feb 2001
Volume 11, Issue 1 - Jan 2001
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Use of semi-active tuned mass dampers for vibration control of force-excited structures
Setareh, Mehdi ;
Structural Engineering and Mechanics, volume 11, issue 4, 2001, Pages 341~356
DOI : 10.12989/sem.2001.11.4.341
A new class of semi-active tuned mass dampers, named as "Ground Hook Tuned Mass Damper" (GHTMD) is introduced. This TMD uses a continuously variable semi-active damper (so called 'Ground-Hook') in order to achieve more reduction in the vibration level. The ground-hook dampers have been used in the auto-industry as a means of reducing the vibration of primary suspension systems in vehicles. This paper investigates the application of this damper as an element of a tuned damper for the vibration reduction of force-excited single degree of freedom (SDOF) models that can be representative of many structural systems. The optimum design parameters of GHTMDs are obtained based on the minimization of the steady-state displacement response of the main mass. The optimum design parameters which are evaluated in terms of non-dimensional values of the GHTMD are obtained for different mass ratios and main mass damping ratios. Using the frequency responses of the resulting systems, performance of the GHTMD is compared to that of equivalent passive TMD, and it is found that GHTMDs are more efficient. A design methodology to obtain the tuning parameters of GHTMD using the relationships developed in this paper is presented.
Evaluation of vertical dynamic characteristics of cantilevered tall structures
Li, Q.S. ; Xu, J.Y. ; Li, G.Q. ;
Structural Engineering and Mechanics, volume 11, issue 4, 2001, Pages 357~372
DOI : 10.12989/sem.2001.11.4.357
In this paper, cantilevered tall structures are treated as cantilever bars with varying cross-section for the analysis of their free longitudinal (or axial) vibrations. Using appropriate transformations, exact analytical solutions to determine the longitudinal natural frequencies and mode shapes for a one step non-uniform bar are derived by selecting suitable expressions, such as exponential functions, for the distributions of mass and axial stiffness. The frequency equation of a multi-step bar is established using the approach that combines the transfer matrix procedure or the recurrence formula and the closed-form solutions of one step bars, leading to a single frequency equation for any number of steps. The Ritz method is also applied to determine the natural frequencies and mode shapes in the vertical direction for cantilevered tall structures with variably distributed stiffness and mass. The formulae proposed in this paper are simple and convenient for engineering applications. Numerical example shows that the fundamental longitudinal natural frequency and mode shape of a 27-storey building determined by the proposed methods are in good agreement with the corresponding measured data. It is also shown that the selected expressions are suitable for describing the distributions of axial stiffness and mass of typical tall buildings.
Stochastic finite element method homogenization of heat conduction problem in fiber composites
Kaminski, Marcin ;
Structural Engineering and Mechanics, volume 11, issue 4, 2001, Pages 373~392
DOI : 10.12989/sem.2001.11.4.373
The main idea behind the paper is to present two alternative methods of homogenization of the heat conduction problem in composite materials, where the heat conductivity coefficients are assumed to be random variables. These two methods are the Monte-Carlo simulation (MCS) technique and the second order perturbation second probabilistic moment method, with its computational implementation known as the Stochastic Finite Element Method (SFEM). From the mathematical point of view, the deterministic homogenization method, being extended to probabilistic spaces, is based on the effective modules approach. Numerical results obtained in the paper allow to compare MCS against the SFEM and, on the other hand, to verify the sensitivity of effective heat conductivity probabilistic moments to the reinforcement ratio. These computational studies are provided in the range of up to fourth order probabilistic moments of effective conductivity coefficient and compared with probabilistic characteristics of the Voigt-Reuss bounds.
Application of softened truss model with plastic approach to reinforced concrete beams in torsion
Lu, Jun-Kai ; Wu, Wen-Hsiung ;
Structural Engineering and Mechanics, volume 11, issue 4, 2001, Pages 393~406
DOI : 10.12989/sem.2001.11.4.393
The present paper discusses the behavior of the reinforced concrete beams subjected to torsion by applying the endochronic plastic model in conjunction with the softened truss model. The endochronic constitutive equations are developed to describe the behavior of concrete. The mechanical behavior of concrete is decomposed into hydrostatic part and deviatoric part. New definition of the bulk modulus and the shear modulus are defined in terms of compressive strength of concrete. Also, new deviatoric hardening function is developed. Then, the endochronic constitutive equations of concrete are applied with the softened truss model for the behavior of the reinforced concrete beams subjected to torsion. The theoretical results obtained based on the present model are compared with the experimental data. The present model has shown the ability to describe the behavior of reinforced concrete beams subjected to torsion.
Stress wave propagation in composite materials
Shen, Siyuan J. ; Pfister, Jens C. ; Lee, James D. ;
Structural Engineering and Mechanics, volume 11, issue 4, 2001, Pages 407~422
DOI : 10.12989/sem.2001.11.4.407
The linear constitutive relations and the failure criteria of composite materials made of thermoviscoelastic solids are presented. The post-failure material behavior is proposed and the dynamic finite element equations are formulated. However, a nonlinear term is kept in the energy equation because it represents the effect of the second law of thermodynamics. A general purpose nonlinear three-dimensional dynamic finite element program COMPASS is upgraded and employed in this work to investigate the interdependence among stress wave propagation, stress concentration, failure progression and temperature elevation in composite materials. The consequence of truthfully incorporating the second law of thermodynamics is clearly observed: it will always cause temperature rise if there exists a dynamic mechanical process.
Second-order analysis of planar steel frames considering the effect of spread of plasticity
Leu, Liang-Jenq ; Tsou, Ching-Huei ;
Structural Engineering and Mechanics, volume 11, issue 4, 2001, Pages 423~442
DOI : 10.12989/sem.2001.11.4.423
This paper presents a method of elastic-plastic analysis for planar steel frames that provides the accuracy of distributed plasticity methods with the computational efficiency that is greater than that of distributed plasticity methods but less than that of plastic-hinge based methods. This method accounts for the effect of spread of plasticity accurately without discretization through the cross-section of a beam-column element, which is achieved by the following procedures. First, nonlinear equations describing the relationships between generalized stresses and strains of the cross-section are derived analytically. Next, nonlinear force-deformation relationships for the beam-column element are obtained through lengthwise integration of the generalized strains. Elastic-plastic flexibility coefficients are then calculated by differentiating the above element force-deformation relationships. Finally, an elastic-plastic stiffness matrix is obtained by making use of the flexibility-stiffness transformation. Adding the conventional geometric stiffness matrix to the elastic-plastic stiffness matrix results in the tangent stiffness matrix, which can readily be used to evaluate the load carrying capacity of steel frames following standard nonlinear analysis procedures. The accuracy of the proposed method is verified by several examples that are sensitive to the effect of spread of plasticity.
Variable-node axisymmetric solid element and its application to adaptive mesh refinement
Choi, Chang-Koon ; Lee, Eun-Jin ; Lee, Wan-Hoon ;
Structural Engineering and Mechanics, volume 11, issue 4, 2001, Pages 443~460
DOI : 10.12989/sem.2001.11.4.443
This paper presents an effective application of a variable-node axisymmetric solid element designated as AQV (Axisymmetric Quadrilateral Variable-node element). The variable-node element with physical midside nodes helps to overcome some problems in connecting the different layer patterns on a quadrilateral mesh in the adaptive h-refinement. This element alleviates the necessity of imposing displacement constraints on irregular (hanging) nodes in order to enforce the inter-element compatibility. Therefore, the elements with variable mid-side nodes can be used effectively in the local mesh refinement for the axisymmetric structures which have stress concentrations. A modified Gaussian quadrature should be adopted to evaluate the stiffness matrices of the variable-node elements mainly because of the slope discontinuity of assumed displacement within the elements. Some numerical examples show the usefulness of variable-node axisymmetric elements in the practical application.
Influence of thickness variation of annular plates on the buckling problem
Ciancio, P.M. ; Reyes, J.A. ;
Structural Engineering and Mechanics, volume 11, issue 4, 2001, Pages 461~468
DOI : 10.12989/sem.2001.11.4.461
The aim of this work is to establish the coefficient that defines the critical buckling load for isotropic annular plates of variable thickness whose outer boundary is simply supported and subjected to uniform pressure. It is assumed that the plate thickness varies in a continuous way, according to an exponential law. The eigenvalues are determined using an optimized Rayleigh-Ritz method with polynomial coordinate functions which identically satisfy the boundary conditions at the outer edge. Good engineering agreement is shown to exist between the obtained results and buckling parameters presented in the technical literature.