Preflex Beams: A Method of Calculation of Creep and Shrinkage Effects
Publication: Journal of Bridge Engineering
Volume 11, Issue 1
Abstract
This paper presents a method of calculation of creep and shrinkage effects for composite beams. It is particularly applicable to Preflex and Flexstress beams, which are composed of a steel I-girder with the bottom flange encased by concrete. The concrete is prestressed by predeflection of the steel beam and the subsequent release after hardening of the concrete flange or by means of prestressing cables. The presented approach using concrete age-adjusted modular ratios allows the calculation of time-dependent stresses in the concrete flange due to creep and shrinkage, with sufficient accuracy for practical applications and without carrying out cumbersome numerical computations. The results can be extended directly to the analysis of ordinary steel–concrete composite beams. The main goal of the present paper is the calibration of the parameters which must be introduced to simplify the equations describing the system. This calibration is discussed and its sensitivity to some calculation inputs is presented. The conclusions are very encouraging and the simplified approach seems to agree very well with the results of the numerical approach.
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Acknowledgments
The writers would like to gratefully acknowledge the support and cooperation of the Laboratoire Central des Ponts et Chaussées (LCPC) of Paris (France), especially J.L. Clément, B. Godart, T. Kretz, F. Toutlemonde, and of the Service d’Etudes Techniques des Routes et Autoroutes (SETRA, France), especially J. A. Calgaro.
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Information & Authors
Information
Published In
Journal of Bridge Engineering
Volume 11 • Issue 1 • January 2006
Pages: 48 - 58
Copyright
© 2006 ASCE.
History
Received: May 30, 2003
Accepted: Feb 9, 2005
Published online: Jan 1, 2006
Published in print: Jan 2006
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