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CONTENTS
Volume 7, Number 5, October 2007
 

Abstract
The purpose of this study is to predict and investigate the time-dependent creep behavior of composite materials. For this, firstly the evaluation method for the modulus of elasticity of whole fiber and matrix is presented from the limited information on fiber volume fraction using the singular value decomposition method. Then, the effects of fiber volume fraction on modulus of elasticity of GFRP are verified. Also, as a creep model, the nonlinear curve fitting method based on the Marquardt algorithm is proposed. Using the existing Findley

Key Words
composite beam; creep; fiber volume fraction; curve fitting method; Marquardt algorithm.

Address
Sung-Yeop Jung; Pyunghwa Institute of Construction Technology, 1474-21, Kwanyang-2-Dong, Dongan-Gu, Anyang City, Kyonggi-Do, 431-810, Korea
Nam-Il Kim and Dong Ku Shin; Department of Civil and Environmental Engineering, Myongji University,
San 38-2, Nam-Dong, Yongin City, Kyonggi-Do, 449-728, Korea

Abstract
In the design of concrete filled composite columns, it is assumed that the load transfer between the steel tube and concrete core has to be achieved by the natural bond. However, it is important to investigate the mechanisms of shear transfer due to the possibility of steel-concrete interface separation. This paper deals with the contribution of headed stud bolt shear connectors and angles to improve the shear resistance of the steel-concrete interface using push-out tests. In order to determine the influence of the shear connectors, altogether three specimens of concrete filled composite column were tested: one without mechanical shear connectors, one with four stud bolt shear connectors and one with four angles. The experimental results showed the mechanisms of shear transfer and also the contribution of the angles and stud bolts to the shear resistance and the force transfer capacity.

Key Words
concrete-filled steel tube; composite action; bond; connections; load transfer; mechanical shear connectors.

Address
Silvana De Nardin; Department of Structural Engineering, University of Sao Paulo at Sao Carlos, Sao Carlos, Brazil
Ana Lucia H. C. El Debs; Avenida Trabalhador Sao-Carlense 400, Centro, Sao Carlos-SP - CEP: 13.566-590, Brazil

Abstract
This paper presents push-out tests of stud shear connectors to examine their fatigue behavior for developing a new composite bridge deck system. The fifteen push-out specimens of D16 mm stud welded on 9 mm steel plate were fabricated according to Eurocode-4, and a series of fatigue endurance test and residual strength test were performed. Additionally, the stiffness and strength variations by cyclic loading were compared. The push-out test, when the stiffness reduction ratio of the specimens was 0.95 under cyclic load, resulted in the failure of the studs. The stiffness variation of the push-out specimens additionally showed that the application of cyclic loads reduced the residual strength. The fatigue strength of the shear connectors were compared with the design values specified in the Eurocode-4, ASSHTO LRFD and JSSC codes. The comparison result showed that the fatigue endurance of the specimens satisfies the design values of these codes.

Key Words
stud shear connector; fatigue behavior; fatigue endurance; residual strength; composite bridge deck system.

Address
Jin-Hee Ahn and Sang-Hyo Kim; School of Civil and Environmental Engineering, Yonsei University, Seoul 120-749, Korea
Youn-Ju Jeong; Structure Research Department, Korea Institute of Construction Technology, Gyeonggi-Do 411-712, Korea

Abstract
This paper presents the development of some numerical models based on the results of laboratory tests performed on axially loaded RC columns strengthened with steel angles and strips. These numerical models consider the nonlinearity of the building materials and the effects of the contact interfaces between different materials. The results of the finite element models accurately describe the general behaviour of the strengthened columns. This study allows engineers to assess the relative importance of the mechanisms acting on the strengthened RC columns. Constructive recommendations are also provided in this paper.

Key Words
RC columns; strengthening; steel angles; strips; finite element modelling; nonlinear analysis.

Address
J. M. Adam; ICITECH, Departamento de Ingenieria de la Construccion y Proyectos de Ingenieria Civil,
Universidad Politecnica de Valencia, Camino de Vera s/n, 46071 Valencia, Spain
S. Ivorra; Departamento de Ingenieria de la Construccion, OO.PP. e Infraestructura Urbana,
Universidad de Alicante, Apartado de Correos 99, 03080 Alicante, Spain
E. Gimenez, J. J. Moragues and P. Miguel; ICITECH, Departamento de Ingenieria de la Construccion y Proyectos de Ingenieria Civil, Universidad Politecnica de Valencia, Camino de Vera s/n, 46071 Valencia, Spain
C. Miragall; Departamento de Mecanica de los Medios Continuos y Teoria de Estructuras, Universidad Politecnica de Valencia, Camino de Vera s/n, 46071 Valencia, Spain
P. A. Calderon; ICITECH, Departamento de Ingenieria de la Construccion y Proyectos de Ingenieria Civil,
Universidad Politecnica de Valencia, Camino de Vera s/n, 46071 Valencia, Spain


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