Keywords: railway bridges, composite steel and concrete, twin girders, temperature gradient, deck deflection.

In the last twenty years, civil engineers have developed structures combining both steel and concrete. In France, one of the most common is the composite twin girder bridge. The use of these bridges is possible only because steel and concrete have the same coefficient of expansion. However, the thermal behaviour is not controlled only by the coefficient of expansion. The other thermal properties of both materials are very different, creating a gradient of temperature between the top of the concrete slab and the bottom of the steel girders, resulting in a vertical deflection at mid span. The impact of this phenomenon on the railway track vertical levelling was specifically noticed on high speed lines where thresholds on track geometry defects for maintenance are much lower than on conventional lines. Defects on track levelling were found during the running of the measurement train on areas with long composite viaducts and rail expansion devices. These areas of expansion devices are always difficult to maintain and maintenance agents could not find the same measurement at night when they came to correct the defect. This was therefore the sign of a high reaction of this type of composite twin girder bridges to temperature. This paper presents the characterisation and understanding of this problem by comparing different models to measurements.

purchase the full-text of this paper (price £22)

go to the previous paper
go to the next paper
return to the table of contents
return to the book description
purchase this book (price £85 +P&P)