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CONTENTS
Volume 13, Number 2, August 2012
 

Abstract
An efficient and accurate algorithm is proposed to evaluate the reliability of cable-stayed bridges accounting for soil-pile interaction. The proposed algorithm integrates the finite-element method and the response surface method. The finite-element method is used to model the cable-stayed bridge including soilpile interaction. The reliability index is evaluated based on the response surface method. Uncertainties in the superstructure, the substructure and load parameters are incorporated in the proposed algorithm. A long span steel cable-stayed bridge with a main span length of 1088 m built in China is considered as an illustrative example. The reliability of the bridge is evaluated for the strength and serviceability performance functions. Results of the study show that when strength limit states for both girder and tower are considered, soil-pile interaction has significant effects on the reliability of steel cable-stayed bridges. Further, a detailed sensitivity study shows that the modulus of subgrade reaction is the most important soil-pile interaction-related parameter influencing the reliability of steel cable-stayed bridges.

Key Words
soil-pile interaction; cable-stayed bridges; structural reliability; response surface method; limit state function.

Address
Jin Cheng : State Key Laboratory for Disaster Reduction in Civil Engineering, Tongji University, Shanghai, China
Xiao-luan Liu : Department of Bridge Engineering, Tongji University, Shanghai, 200092, China

Abstract
Steel plate-masonry composite structure is a newly-developed type of structural technique applicable to existing masonry buildings by which the load-bearing walls can be removed for large spaces. This kind of structure has been used in practice for its several advantages, but experimental investigation on its elements is nearly unavailable in existing literature. This paper presents an experimental study on the flexural behaviour of four steel plate-masonry composite beams loaded by four-point bending. Test results indicate that failure of the tested beams always starts from the local buckling of steel plate, and that the tested beams can satisfy the requirement of service limit state. In addition, the assumption of plane section is still remained for steel plate prior to local buckling or steel yielding. By comparative analyses, it was also verified that the working performance of the beam is influenced by the cross-section of steel plate, which can be efficiently enhanced by epoxy adhesive rather than cement mortar or nothing at all. Besides, it was also found that the contribution of the encased masonry to the flexural capacity of the composite beam cannot be ignored when the beam is injected with epoxy adhesive.

Key Words
steel plate; injection material; composite beam; local buckling.

Address
Deng-Hu Jing*, Shuang-Yin Cao : School of Civil Engineering, Southeast University, Nanjing, Jiangsu, 210096, China
Lei Shi : Green Town Architecture Design Co., Ltd., Hangzhou, Zhejiang, 310013, China

Abstract
Serviceability rather than strength is the most critical design requirement for vibrationvulnerable floor constructions. Annoying vibrations due to normal walking activity have been observed more frequently on long-span lightweight floor systems in office and commercial retail buildings, raising the need for the development of floor vibration design procedures. This paper highlights some limitations of one of the most commonly used guidelines AISC/CISC DG11, and proposes improvements to this method. Design charts and approximate closed form formulas to estimate the walking response are developed in which various factors relating to the dynamic characteristics of both the floor and the excitation are considered. The accuracy of the proposed formulas and other proposals found in the literature is examined. The proposed modifications would be significant, especially with long-span floors where vibration levels may be underestimated by the current design procedure. The application of the proposed prediction method is illustrated by worked examples that reveal a good agreement with results obtained from finite element analyses and experiments. The presented work would enhance the accuracy and maintain the simplicity and convenience of the design guideline.

Key Words
composite floors; floor vibrations; serviceability; steady state; resonant; walking force; harmonic.

Address
T.H. Nguyen*, E.F. Gad, J.L. Wilson : Faculty of Engineering and Industrial Sciences, Swinburne University of Technology, VIC 3122, Australia
N. Haritos : Department of Infrastructure Engineering, The University of Melbourne, VIC 3010, Australia

Abstract
Shell structures are very interesting from the design point of view and these are well recognized in the scientific literature. In this paper the analysis of the buckling loads and stability paths of a sandwich conical shell with unsymmetrical faces under combined load based on the assumptions of moderately large deflections (geometrically nonlinear theory) is considered and elastic-plastic properties of the material of the faces are taken into considerations. External load is assumed to be two-parametrical one and it is assumed that the shell deforms into the plastic range before buckling. Constitutive relations in the analysis are those of the Nadai-Hencky deformation theory of plasticity and Prandtl-Reuss plastic flow theory with the H-M-H (Huber-Mises-Hencky) yield condition. The governing stability equations are obtained by strain energy approach and Ritz method is used to solve the equations with the help of analytical-numerical methods using computer.

Key Words
shells; elastic-plastic stability; deformation theory of plasticity; large displacements; strain energy.

Address
Poznan University of Technology, Institute of Applied Mechanics, Piotrowo 3, 60-965 Poznan, Poland

Abstract
The calculation of fire resistance for a composite structural element comprises the calculation of the temperature within its cross-section and of the load bearing capacity, considering the evolution of the steel and concrete mechanical properties, function of the temperature. The paper proposes a method to calculate the bending capacity under ISO fire, for Slim Floor systems using asymmetric steel beams, with a wider lower flange or a narrow upper flange welded onto a half hot-rolled profile. The temperatures in the cross-section are evaluated by means of empirical formulas determined through a parametrical analysis, performed with the special purpose non-linear finite element program SAFIR. Considering these formulas, the bending capacity may be calculated, using an analytical approach to determine the plastic bending moment, for different fire resistance demands. The results obtained with this simplified method are validated through numerical analysis.

Key Words
slim floor; fire design; ISO fire; simplified method.

Address
R. Zaharia : The Politehnica University of Timisoara, Timisoara, Romania
J. M. Franssen : University of Liege, Liege, Belgium

Abstract
In this study, fracture analysis of orthotropic FGM (Functionally Graded Material) plate having center crack is performed, numerically. Material axis arbitrarily oriented and there is an angle θ° between material and crack axes. Stress intensity factors at the crack tips for Mode I are calculated using Displacement Correlation Method (DCM). In numerical analysis, effects of material properties and variation of angle θ° between material and crack axes on the fracture behavior are investigated for four different boundary conditions. Consequently, it is found that the effect of θ° on stress intensity factor depends on variation of material properties.

Key Words
orthotropic functionally graded materials; displacement correlation method; finite element analysis; stress intensity factor; aerospace structures

Address
Mete Onur Kaman : Firat University, Department of Mechanical Engineering, Elazig, Turkey
Fatih Cetisli : Firat University, Department of Civil Engineering, Elazig, Turkey


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