Title: Design Optimization of a Continuous Railway Bridge with Prebent and Prestressed Composite Decks

Author(s): S. Staquet, H. Detandt, and B. Espion

Publication: Symposium Paper

Volume: 246

Issue:

Appears on pages(s): 87-106

Keywords: creep recovery; heat cure; precast; shrinkage; time-dependent

DOI: 10.14359/18981

Date: 9/1/2007

Abstract:
Previously, a significant research effort was made to analyse the long-term behaviour of a kind of composite steel-concrete, prebent and prestressed beam used extensively in Belgium as simply supported railway bridge decks. They are trough type with U shaped cross section. Parallel with that, an extensive experimental research has been carried out to extend the Belgian technique of steel-concrete prebent beams to Very High Performance Concrete (VHPC). The main advantage of using VHPC instead of the C50 concrete currently used is to decrease the prestressing losses of the system thanks to a significant decrease of the creep deformations. One of the motivations behind this research was to develop realistic models to assess the feasability of constructing continuous railway bridges by connecting such simple decks over intermediate supports. For railway bridge decks, the condition of no cracking under load is paramount. This implies to devise a form of in situ prestressing of the connection between the simply supported decks. A structural analysis program was developed that could cope with multiple phases of construction and loading for such a highly heterogeneous structure. The structural analysis is performed within the framework of beam-type displacement-based finite element analysis. A step-by-step time-dependent analysis is based on the algorithm of superposition. The creep and shrinkage model is the CEB-FIP MC 90 model, which was found to best reproduce the strains recorded in the laboratory creep and shrinkage tests for the C50/60 concrete of the singly supported decks and for the C80/95 VHPC. Creep recovery effects occurring at unloading have been accommodated in the step-by-step time-dependent analysis with the two-function method proposed by Yue and Taerwe. The purpose of this paper is to present a design optimization study of the construction phases of a continuous bridge with prebent and prestressed composite decks. The most influential parameters on the long-term behavior of the continuous bridge are analyzed.