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CONTENTS
Volume 8, Number 2, April 2008
 

Abstract
This paper presents the theoretical simulation of the response of 1020 carbon steel tubes subjected to symmetric and unsymmetric cyclic bending with or without external pressure by using the endochronic theory. Experimental data of 1020 carbon steel tubes tested by Corona and Kyriakides (1991) were used for evaluating the theoretical simulation. Several cases were considered in this study, they were symmetric bending without external pressure, symmetric bending with external pressure, unsymmetric bending without external pressure, and unsymmetric bending with external pressure. The responses of the moment-curvature, ovalization-curvature and ovalization-number of cycles with or without external pressure were discussed. It has been shown that the theoretical simulations of the responses correlate well with the experimental data.

Key Words
endochronic theory; 1020 carbon steel tubes; unsymmetric cyclic bending; external pressure; moment; curvature, ovalization.

Address
Kuo-Long Lee; Department of Computer Application Engineering, Far East College Tainan, Taiwan, R.O.C.
Chien-Min Hsu; Department of Art-Craft, Tung Fang Institute of Technology Kao Hsiung County, Taiwan, R.O.C.
Chao-Yu Hung; Department of Mechanical Engineering, R.O.C. Military Academy, Kaohsiung, Taiwan, R.O.C.

Abstract
A method is proposed to estimate the ultimate strength of rectangular concrete-filled steel tubular (CFT) stub columns under axial compression. The ultimate strength of concrete core is determined by using the conception of the effective lateral confining pressure and a failure criterion of concrete under true triaxial compression, which takes into account the difference between the lateral confining pressure provided by the broad faces of the steel tube and that provided by the narrow faces of the steel tube. The longitudinal steel strength of broad faces and that of the narrow faces of the steel tube are calculated respectively due to that buckling tends to occur earlier and more extensively on the broader faces. Finally, the proposed method is verified with experimental results. Corresponding values of ultimate strength calculated by ACI (2005), AISC (1999) and GJB4142-2000 are given respectively for comparison. It is found from comparison that the proposed method shows a good agreement with the experimental results.

Key Words
concrete-filled steel tubular; ultimate strength; axial compression; failure criterion; true triaxial compression.

Address
Department of Civil Engineering, South China University of Technology, Guangzhou 510641, China

Abstract
This paper demonstrates an application of the perturbation based stochastic finite element method (SFEM) for predicting the performance of structural systems made of composite sections with random material properties. The composite member consists of materials in contact each of which can surround a finite number of inclusions. The perturbation based stochastic finite element analysis can provide probabilistic behavior of a structure, only the first two moments of random variables need to be known, and should therefore be suitable as an alternative to Monte Carlo simulation (MCS) for realizing structural analysis. A summary of stiffness matrix formulation of composite systems and perturbation based stochastic finite element dynamic analysis formulation of structural systems made of composite sections is given. Two numerical examples are presented to illustrate the method. During stochastic analysis, displacements and sectional forces of composite systems are obtained from perturbation and Monte Carlo methods by changing elastic modulus as random variable. The results imply that perturbation based SFEM method gives close results to MCS method and it can be used instead of MCS method, especially, if computational cost is taken into consideration.

Key Words
stochastic finite element method; stochastic perturbation technique; composite; stiffness matrix; monte carlo simulation.

Address
Karadeniz Technical University, Department of Civil Engineering, 61080, Trabzon, Turkey

Abstract
n slender sections there is a substantial post-buckling strength provided after the formation of local buckling waves. These waves happened due to normal stresses or shear stresses or both. In this study, a numerical investigation of the behavior of slender I-section beams in combined pure bending and shear has been described. The studied cases were assumed to be prevented from lateral torsional buckling. To achieve this aim, a finite element model that simulates the geometric and material nonlinear nature of the problem has been developed. Moreover, the initial geometric imperfections were included in the model. Different flange and web width-thickness ratios as well as web panel aspect ratios have been considered to draw complete set of interaction diagrams. Results reflect the interaction behavior between flange and web in resisting the combined action of moments and shear. In addition, the web panel aspect ratio will not significantly affect the combined ultimate shear-bending strength as well as the post local buckling strength gained by the section. Results are compared with that predicted by both the Eurocode 3 and the American Iron and Steel specifications, AISI?001. Finally, an empirical interaction equation has been proposed.

Key Words
steel; stability; bending; shear; strength; local buckling.

Address
M. El Aghoury; Department of Structural Engineering, Ain Shams University, El-Sarayat Street, Abbassia, P.O. Box 11517, Egypt
M. T. Hanna; Department of Structure and Metallic Construction, Housing and Building Research Center, 87 El-Tahreer Street, Dokki, P.O. Box 1770, Egypt

Abstract
An analytical procedure is presented for the determination of the buckling load and the buckling temperature of a straight, slender, geometrically perfect, axially loaded, translationally and rotationally restrained steel column exposed to fire. The exact kinematical equations of the column are considered, but the shear strain is neglected. The linearized stability theory is employed in the buckling analysis. Behaviour of steel at the elevated temperature is assumed in accordance with the European standard EC 3. Theoretical findings are applied in the parametric analysis of restrained columns. It is found that the buckling length factor decreases with temperature and depends both on the material model and stiffnesses of rotational and translational restraints. This is in disagreement with the buckling length for intermediate storeys of braced frames proposed by EC 3, where it is assumed to be temperature independent. The present analysis indicates that this is a reasonable approximation only for rather stiff rotational springs.

Key Words
restrained steel column; inelastic buckling; Reissner beam; high temperatures; critical temperature.

Address
Tomaz Hozjan1,2*, Igor Planinc1, Miran Saje1 and Stanislav Srpcic1;
1University of Ljubljana, Faculty of Civil and Geodetic Engineering, Jamova 2, SI-1115 Ljubljana, Slovenia
2Trimo d.d., Prijateljeva cesta 12, 8210 Trebnje, Slovenia


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