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CONTENTS
Volume 6, Number 5, October 2006
 

Abstract
This paper describes the results of a numerical investigation of the large deflection behaviour of steel beams under fire conditions, taking into consideration the effect of catenary action provided by the surrounding structures. The main focus is on the development, validation and application of a simplified calculation method that may be adopted in design calculations. Because no experimental result is available for validation of the simplified calculation method, the finite element program ABAQUS has been used to simulate the large deflection behaviour of a number of steel beams so as to provide alternative results for validation of the proposed method. Utilising catenary action has the potential of eliminating fire protection to all steel beams without causing structural failure in fire. However, practical application of catenary action will be restricted by concerns over large beam deflection causing integrity failure of the fire resistant compartment and additional cost of strengthening the connections and the surrounding structures to resist the catenary forces in the steel beams. This paper will provide a discussion on practical implications of utilising catenary action in steel beams as a means of eliminating fire protection. A number of examples will then be provided to illustrate the type of steel framed structure that could benefit the most from exploiting catenary action in fire resistant design.

Key Words
large deflection; fire resistant design; catenary action; steel beams; fire engineering; integrity of fire compartment.

Address
School of Mechanical, Aerospace and Civil Engineering, The University of Manchester, UK

Abstract
This paper discusses the composite mechanism and its effect upon the behavior of a steel reinforced concrete (SRC) member subjected to a flexural load. The relationship between member strength and deformation is established using the bond strength between the steel and reinforced concrete. An analytical model is proposed and used to incorporate the sectional strains and bond strength at the elastic and inelastic stages for moment-curvature relationship derivation. The results from the flexural load tests are used to validate the accuracy of the proposed model. Comparisons between the experimental information and the analytical results demonstrate close moment-curvature relevance, which justifies the applicability of the proposed method.

Key Words
bond mechanism; bond strength; flexural behavior; deformation; composite members.

Address
Department of Civil Engineering, National Central University, Chung-Li 32054, Taiwan

Abstract
Based on a non-linear model taking into account flexural-torsional couplings, analytical solutions are derived for lateral buckling of simply supported I beams under some representative load cases. A closed form is established for lateral buckling moments. It accounts for bending distribution, load height application and pre-buckling deflections. Coefficients C1 and C2 affected to these parameters are then derived. Regard to well known linear stability solutions, these coefficients are not constant but depend on another coefficient k1 that represents the pre-buckling deflection effects. In numerical simulations, shell elements are used in mesh process. The buckling loads are achieved from solutions of eigenvalue problem and by bifurcations observed on non linear equilibrium paths. It is proved that both the buckling loads derived from linear stability and eigenvalue problem lead to poor results, especially for I sections with large flanges for which the behaviour is predominated by pre-buckling deflection and the coefficient k1 is large. The proposed solutions are in good agreement with numerical bifurcations observed on non linear equilibrium paths.

Key Words
buckling; finite element; eigenvalue; linear stability; non linear stability; open section; pre-buckling; thin-walled beam.

Address
F. Mohri(1,2) and M. Potier-Ferry(2)rn1) IUT Nancy-Brabois, D?artement G?ie Civil, Universit?Henri Poincar? Nancy 1, 54601 Villers les Nancy, Francern2) LPMM, UMR CNRS 7554, ISGMP, Universit?Paul Verlaine-Metz, Ile du Saulcy, 57045 Metz, France

Abstract
In this paper, a non-linear structural analysis software with pro-processing and post-recessing function is proposed by the author. The software incorporating the functions of the structural analysis and geometrical design of Tensegrity structures. Using this software, Cable Dome is analyzed as a prototype, a comprehensive study on the structural behavior of Tensegrity domes is presented in detail. Design methods of Tensegrity domes were proposed. Based on the analysis, optimizing design was performed. Several new Tensegrity domes with different geometrical design scheme are proposed, the structural analysis of the new schemes is also conducted. The analysis result shows that the proposed new forms of the Tensegrity domes are reasonable for practical applications.

Key Words
tensegrity; non-linear; prestressed force; self-equilibrium.

Address
School of Civil Engineering, University of Leeds, LS2 9JT Leeds, U.K.

Abstract
The paper presents the cost optimization of composite floor trusses composed from a reinforced concrete slab of constant depth and steel trusses consisting of hot rolled channel sections. The optimization was performed by the nonlinear programming approach, NLP. Accordingly, a NLP optimization model for composite floor trusses was developed. An accurate objective function of the manufacturing material, power and labour costs was proposed to be defined for the optimization. Alongside the costs, the objective function also considers the fabrication times, and the electrical power and material consumption. Composite trusses were optimized according to Eurocode 4 for the conditions of both the ultimate and the serviceability limit states. A numerical example of the optimization of the composite truss system presented at the end of the paper demonstrates the applicability of the proposed approach.

Key Words
structural optimization; nonlinear programming; NLP; composite trusses; composite floor trusses; welded structures.

Address
Faculty of Civil Engineering, University of Maribor, Smetanova ulica 17, SI-2000 Maribor, Slovenia


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