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CONTENTS
Volume 10, Number 2, April 2010
 

Abstract
The expediency of using tubular composite steel and concrete columns of annular cross-sections in construction is discussed. The new type space framework with tubular composite columns of multi-storey buildings and its rigid beam-column joints are demonstrated. The features of interaction between the circular steel tube and spun concrete stress-strain states during the concentrical and eccentrical loading of tubular composite members are considered. The modeling of the bearing capacity of beam-columns of composite annular cross-sections is based on the concepts of bending with a concentrical force and compression with a bending moment. The comparison of modeling results for the composite cross-sections of beam-columns is analysed. The expediency of using these concepts for the limit state verification of beam-columns in the methods of the partial safety factors design (PSFD) legitimated in Europe and the load and resistance factors design (LRFD) used in other countries is presented and illustrated by a numerical example.

Key Words
composite structures; composite frame; composite annular cross-section; beam-column; eccentric compression.

Address
A.K. Kvedaras: Department of Steel and Timber Structures, Vilnius Gediminas Technical University, Vilnius, LT-10223,
Lithuania
A. Kudzys: KTU Institute of Architecture and Construction, Kaunas, LT-44405, Lithuania

Abstract
The objective of this study is to formulate a general 3D material-structural analysis framework for the thermomechanical behavior of steel-concrete structures in a fire environment. The proposed analysis framework consists of three sequential modeling parts: fire dynamics simulation, heat transfer analysis, and a thermomechanical stress analysis of the structure. The first modeling part consists of applying the NIST (National Institute of Standards and Technology) Fire Dynamics Simulator (FDS) where coupled CFD (Computational Fluid Dynamics) with thermodynamics are combined to realistically model the fire progression within the steel-concrete structure. The goal is to generate the spatial-temporal (ST) solution variables (temperature, heat flux) on the surfaces of the structure. The FDS-ST solutions are generated in a discrete form. Continuous FDS-ST approximations are then developed to represent the temperature or heat-flux at any given time or point within the structure. An extensive numerical study is carried out to examine the best ST approximation functions that strike a balance between accuracy and simplicity. The second modeling part consists of a finite-element (FE) transient heat analysis of the structure using the continuous FDS-ST surface variables as prescribed thermal boundary conditions. The third modeling part is a thermomechanical FE structural analysis using both nonlinear material and geometry. The temperature history from the second modeling part is used at all nodal points. The ABAQUS (2003) FE code is used with external user subroutines for the second and third simulation parts in order to describe the specific heat temperature nonlinear dependency that drastically affects the transient thermal solution especially for concrete materials. User subroutines are also developed to apply the continuous FDS-ST surface nodal boundary conditions in the transient heat FE analysis. The proposed modeling framework is applied to predict the temperature and deflection of the well-documented third Cardington fire test.

Key Words
fire-dynamics; nonlinear finite elements; transient heat; steel-concrete; composite; structural behavior; fire simulation.

Address
Joonho Choi: School of Civil and Environmental Engineering, Georgia Institute of Technology, Atlanta,
GA 30332-0355, USA
Heesun Kim: College of Engineering, EWHA Womans University, 11-1 Daehyun-Dong, Seodaemun-Gu,
Seoul, South Korea
Rami Haj-ali: School of Civil and Environmental Engineering, Georgia Institute of Technology, Atlanta,
GA 30332-0355, USA

Abstract
The subject of the paper is an isotropic metal foam rectangular plate. Mechanical properties of metal foam vary continuously through plate of the thickness. A nonlinear hypothesis of deformation of plane cross section is formulated. The system of partial differential equations of the plate motion is derived on the basis of the Hamilton\'s principle. The system of equations is analytically solved by the Bubnov-Galerkin method. Numerical investigations of dynamic stability for family rectangular plates with respect analytical solution are performed. Moreover, FEM analysis and theirs comparison with results of numerical-analytical calculations are presented in figures.

Key Words
metal foam plate; dynamic stability; elastic buckling; shear effect.

Address
D. Debowski: Institute of Mechanical Engineering and Machine Operation, University of Zielona Gora, ul. Podgorna 50, PL. 65-246 Zielona Gora, Poland
K. Magnucki: Institute of Applied Mechanics, Poznan University of Technology, ul. Piotrowo 3, PL. 60-965 Poznan, Poland
M. Malinowski: Institute of Mechanical Engineering and Machine Operation, University of Zielona Gora, ul. Podgorna 50, PL. 65-246 Zielona Gora, Poland


Abstract
The present work describes the experimental tests on steel and lightweight concrete composite beams performed at University of Minho, Portugal. The study involves tests on simply supported composite beams of 4.5 m span, with the same geometrical disposition, supports and materials. The geometrical configuration for the cross section and supports is identical for every beam, varying the shear connectors

Key Words
composite beams; lightweight concrete; shear connection; headed studs.

Address
Isabel B. Valente: ISISE, Department of Civil Engineering, University of Minho Azurem, 4800-058 Guimaraes, Portugal
Paulo J.S. Cruz: ISISE, Department of Architecture, University of Minho Azurem, 4800-058 Guimaraes, Portugal

Abstract
The existing CFT columns present the deterioration in confining effect after the yield of steel tube, local buckling and the deterioration in load capacity. If lateral load such as earthquake load is applied to CFT columns, strong shearing force and moment are generated at the lower part of the columns and local buckling appears at the column. In this study, axial compression test and beam-column test were conducted for existing CFT square column specimens and those reinforced with carbon fiber sheets (CFS). The variables for axial compression test were width-thickness ratio and the number of CFS layers and those for beamcolumn test were concrete strength and the number of CFS layers. The results of the compression test showed that local buckling was delayed and maximum load capacity improved slightly as the number of layers increased. The specimens

Key Words
concrete filled steel tube; CFT, composite column; confining effect; carbon fiber sheet.

Address
Park, Jai Woo: University of Seoul, Department of Architecture Engineering, Seoul, Korea
Hong, Young Kyun: Hongik University, Department of Architecture, Seoul, Korea.
Choi, Sung Mo: University of Seoul, Department of Architecture Engineering, Seoul, Korea


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