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CONTENTS
Volume 10, Number 5, November 2000
 

Abstract
The formulas for the perturbation analysis with modes of close eigenvalues are derived in this paper. Emphasis is made on the consistency of the straightforward perturbation process, given the complete terms of perturbations in the zeroth-order, which is a form of Rayleigh quotient, and in the higher-orders. By dividing the perturbation of eigenvector into two parts, the first-order perturbation with respect to the modes of close eigenvalues is moved into the zeroth-order perturbation. The normality condition is employed to compute the higher-order perturbations of eigenvector. The algorithm can be condensed to a single mode with a distinct eigenvalue, and this can accelerate the convergence of the perturbation analysis. The example confirms that the perturbation approximation obtained from the suggested procedure is in a good accuracy on the eigenvalues, eigenvectors, and normality.

Key Words
eigenvalue problem, close eigenvalues, perturbation analysis

Address
Laboratorio Nacional de Engenharia Civil, Avenida do Brasil, 101, 1700-066 Lisboa Codex, Portugal

Abstract
In this study, the state equation for axisymmetric bending of laminated transversely isotropic circular plates on elastic foundation is established on the basis of three-dimensional elasticity. By using the expansions of Bessel functions, an analytical solution of the problem is presented. As a result, all the fundamental equations of three-dimensional elasticity can be satisfied exactly and all the independent elastic constants can be fully taken into account. Furthermore, the continuity conditions at the interfaces of plies can also be satisfied.

Key Words
laminated circular plate, state equation, elastic foundation, analytical solution

Address
Sheng HY, Hefei Univ Technol, Dept Architectural Engn, Hefei 230009, Anhui, Peoples R China
Hefei Univ Technol, Dept Architectural Engn, Hefei 230009, Anhui, Peoples R China

Abstract
Buckling loads are determined for thin isotropic circular cylindrical shell panels subject to radial pressure using the new differential quadrature method. The Budiansky stability theory serves as the basis of the analysis. For this problem involving four boundary lines a two-dimensional approach is used, and a detailed convergence study is carried out to determine the appropriate analysis parameters for the method. Numerical results are determined for a total of twelve cylindrical shell panel cases for a number of different boundary support conditions. The results are compared with analytical and finite element method results. Conclusions are drawn about the technical significance of the results and the solution process.

Key Words
stability analysis, cylindrical panels, differential quadrature method

Address
Redekop D, Univ Ottawa, Dept Mech Engn, Ottawa, ON K1N 6N5, Canada
Univ Ottawa, Dept Mech Engn, Ottawa, ON K1N 6N5, Canada

Abstract
An iterative procedure for the analysis of reinforced concrete frames with beams in cracked state is presented. ACI and CEB model equations are used for the effective moment of inertia of the cracked members. In the analysis, shear deformations are taken into account and reduced shear stiffness is considered by using effective shear modulus models available in the literature. Based on the aforementioned procedure, a computer program has been developed. The results of the computer program have been compared with the experimental results available in the literature and found to be in good agreement. Finally, a parametric study is carried out on a two story reinforced concrete frame.

Key Words
reinforced concrete frames, analysis, effective moment of inertia, effective shear modulus, deflections, beam in cracked state

Address
Tanrikulu AK, Cukurova Univ, Dept Civil Engn, TR-01330 Adana, Turkey
Cukurova Univ, Dept Civil Engn, TR-01330 Adana, Turkey

Abstract
Based on the stiffness equation of the tapered beam element involving the effects of axial force and shear deformation, numerical investigations are carried out on elastic instability for web-linearly tapered columns with I-section of steel portal frames. Effects of shear deformation on the effective length of the tapered columns with I-section are studied. An efficient approach for determining the effective length of the tapered portal frame columns considering effects of shear deformation is proposed.

Key Words
tapered column with I-section, effective length, finite element, shear deformation, steel portal frame

Address
Li GQ, Tongji Univ, Dept Bldg & Struct Engn, Shanghai 200092, Peoples R China
Tongji Univ, Dept Bldg & Struct Engn, Shanghai 200092, Peoples R China

Abstract
This paper is a presentation of a physical model for the elastic-partly plastic behavior of rectangular hollow section pinned struts subjected to static cyclic axial loading and the evaluation of the compressive strength of retrofitted damaged struts. Retrofitting is achieved by welding stiffening plates along the webs of damaged struts. The shape of the elastic and permanent deformations of the strut axis satisfy the conditions at the ends and midspan. Continuous functions of the geometric variables of stress distributions in the yielded zone are evaluated by interpolation between three points along each partly plastic zone. Permanent deformations of the partly plastic region are computed and used to update the shape of the unloaded strut. The necessity of considering geometric nonlinearity is discussed. The sensitivity of the results to the location of interpolation points, the shape of the permanent deformation and material hysteretic properties is investigated.

Key Words
bracing, compressive strength, cyclic loads, geometric nonlinearity, hysteresis, partial plasticity, retrofitting, steel, struts

Address
Univ Western Australia, Nedlands, WA 6907, Australia

Abstract
This paper is a presentation of an experimental study about the elastic-partly plastic behavior of rectangular hollow steel pinned struts subjected to static cyclic axial loading and the evaluation of the compressive strength of retrofitted crooked struts. Retrofitting is achieved by welding stiffening plates along the webs of damaged struts. The material follows a quasi-kinematic hardening hysteresis path as observed from coupon tests. Test results are compared to those of an analytical model showing a good agreement for both standard and retrofitted struts. The comparison of different stiffener plate dimensions shows that more efficient strengthening is achieved by using long thin stiffeners rather than short thick ones.

Key Words
bracing, compressive strength, cyclic loads, hysteresis, partial plasticity, retrofitting, steel, struts, testing

Address
Boutros M, Univ Western Australia, Nedlands, WA 6907, Australia
Univ Western Australia, Nedlands, WA 6907, Australia


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