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CONTENTS
Volume 7, Number 4, August 2007
 

Abstract
A finite element implementation of the modified compression field theory (MCFT) using a tangential formulation is presented in this work. Previous work reported on implementations of MCFT has concentrated mainly on secant formulations. This work describes details of the implementation of a modular algorithmic structure of a reinforced concrete constitutive model in nonlinear finite element schemes that use a Jacobian matrix in the solution of the nonlinear system of algebraic equations. The implementation was verified and validated using experimental and analytical data reported in the literature. The developed algorithm, which converges accurately and quickly, can be easily implemented in any finite element code.

Key Words
finite elements; reinforced concrete; compression field theory; nonlinear analysis; shear.

Address
School of Civil and Environmental Engineering, Cornell University, Ithaca, NY 14853, USA

Abstract
(Received January 2, 2007, Accepted May 31, 2007) Abstract. When coupling beams are proportioned appropriately in coupled core wall (CCW) systems, the input energy from ground motions is dissipated primarily through inelastic deformations in plastic hinge regions at the ends of the coupling beams. It is desirable that the plastic hinges form at the beam ends while the base wall piers remain elastic. The strength and stiffness of the coupling beams are, therefore, crucial if the desired global behavior of the CCW system is to be achieved. This paper presents the results of nonlinear response history analysis of two 20-story CCW buildings. Both buildings have the same geometric dimensions, and the components of the buildings are designed based on the equivalent lateral force procedure. However, one building is fitted with steel coupling beams while the other is fitted with diagonally reinforced concrete coupling beams. The force-deflection relationships of both beams are based on experimental data, while the moment-curvature and axial load-moment relationships of the wall piers are analytically generated from cross-sectional fiber analyses. Using the aforementioned beam and wall properties, nonlinear response history analyses are performed. Superiority of the steel coupling beams is demonstrated through detailed evaluations of local and global responses computed for a number of recorded and artificially generated ground motions.

Key Words
coupled core wall; coupling beam; dynamic analysis; hysteresis; nonlinear analysis; seismic loading; time-history.

Address
Patrick J. Fortney; Department of Civil Engineering, Clemson University, Clemson, SC 29634, USA
Bahram M. Shahrooz and Gian A. Rassati;Department of Civil and Environmental Engineering, University of Cincinnati, Cincinnati, OH 45212, USA

Abstract
The objective of this study is to clarify the structural features of members consisting of connection, as a series of the previous study on the CFT column-to-beam tensile connection with combined cross diaphragm. This connection has the merits that the stress is distributed evenly on the beam flange and the diaphragm and the stress concentration is reduced, by improving the stress transfer route and restraining abrupt deformation of diaphragm. The finite element analysis was performed to find out the stress transfer through sleeve which is an important member of the connection with combined cross diaphragm. The length and thickness of sleeve were used as variables for the analysis. As the analysis results, the length and thickness of sleeve didn

Key Words
concrete filled steel tube; combined cross diaphragm; sleeve; FEM; ANSYS.

Address
Sung-Mo Choi and Do-Sub Jung; Department of Architectural Engineering, University of Seoul, Seoul, Korea
Dae-Joong Kim; Engineering & Construction Department of Samsung Corporation, Sungnam-Si, Kyungkido, Korea
Jin-Ho Kim; Research Institute of Indurstrial Science & Technology Steel Structure Research Laboratory,
Kyungkido, 445-813, Korea

Abstract
Ehab Ellobody? Department of Structural Engineering, Faculty of Engineering, Tanta University, Tanta, Egypt Ben Young? Department of Civil Engineering, The University of Hong Kong, Pokfulam Road, Hong Kong (Received September 13, 2006, August 13, 2007) Abstract. The investigation on the behaviour of cold-formed stainless steel non-slender circular hollow section columns is presented in this paper. The normal strength austenitic stainless steel type 304 and the high strength duplex materials (austenitic-ferritic approximately equivalent to EN 1.4462 and UNS S31803) were considered in this study. The finite element method has been used to carry out the investigation. The columns were compressed between fixed ends at different column lengths. The geometric and material nonlinearities have been included in the finite element analysis. The column strengths and failure modes were predicted. An extensive parametric study was carried out to study the effects of normal and high strength materials on cold-formed stainless steel non-slender circular hollow section columns. The column strengths predicted from the finite element analysis were compared with the design strengths calculated using the American Specification, Australian/New Zealand Standard and European Code for cold-formed stainless steel structures. The numerical results showed that the design rules specified in the American, Australian/New Zealand and European specifications are generally unconservative for the cold-formed stainless steel non-slender circular hollow section columns of normal and high strength materials, except for the short columns and some of the high strength stainless steel columns. Therefore, different values of the imperfection factor and limiting slenderness in the European Code design rules were proposed for cold-formed stainless steel non-slender circular hollow section columns.

Key Words
buckling; circular hollow sections; finite element; non-slender; normal strength; high strength; stainless steel; structural design.

Address
Ehab Ellobody; Department of Structural Engineering, Faculty of Engineering, Tanta University, Tanta, Egypt
Ben Young; Department of Civil Engineering, The University of Hong Kong, Pokfulam Road, Hong Kong

Abstract
Arched Corrugated Steel Roof (ACSR) is a kind of thin-walled steel shell, composing of arched panels with transverse small corrugations. Four full-scale W666 ACSR samples with 18m and 30m span were tested under full and half span static vertical uniform loads. Displacement, bearing capacities and failure modes of the four samples were measured. The web and bottom flange in ACSR with transverse small corrugations are simplified to anisotropic curved plates, and the equivalent tensile modulus, shear modulus and Poisson\'s ratio of 18m span ACSR were measured. Two 18 m-span W666 ACSR samples were analyzed with the Finite Element Analysis program ABAQUS. Base on the tests, the limit bearing capacity of ACSR is low, and for half span loading, it is 74-75% compared with the full span loading. When the testing load approached to the limit value, the bottom flange at the sample\'s bulge place locally buckled first, and then the whole arched roof collapsed suddenly. If the vertical loads apply along the full span, the deformation shape is symmetric, but the overall failure mode is asymmetric. For half span vertical loading, the deformation shape and the overall failure mode of the structure are asymmetric. The ACSR displacement under the vertical loads is large and the structural stiffness is low. There is a little difference between the FEM analysis results and testing data, showing the simplify method of small corrugations in ACSR and the building techniques of FEM models are rational and useful.

Key Words
Arched Corrugated Steel Roof (ACSR); full-scale samples; static tests; transverse small corrugations; anisotropic plates; finite element analysis.

Address
School of Civil Engineering and Architecture, Wuhan University of Technology, Wuhan, 430070, China


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