Henri Detandt

ANALYSIS OF THE CAMBER AT PRESTRESSING OF A NEW KIND OF COMPOSITE RAILWAY BRIDGE DECK

Publisher Summary Up to 300 composite railway bridge decks of a new kind, belonging to the trough type with U shaped cross section, have been constructed in Belgium for 10 years. They seem to perform according to expectations. However, this chapter has some concerns about the variability between the measured and computed camber of these bridge decks just after the transfer of pre-stressing. In order to explain this variability, the chapter makes a statistical analysis with a sample of 42 bridge decks using 10 variables like the concrete compressive strength, the heat cure, the type of steel girder, and the age of concrete at pre-stressing. The ratio between maximum tensile stress and yield strength in the steel girders at the pre-flexion and the type of steel girder are found to be the most significant variables to explain the variability. If the steel girder is hot-rolled and the tensile stress/yield strength ratio in the steel girders at the pre-flexion is high, then the difference between the measured and computed cambers is high too. So, the construction process of the steel girders is important because of its influence during the elastification phase. The purpose of the chapter is to report on this statistical analysis in order to explain the influence of each of these variables on the behavior of these composite railway bridge decks.

Comportement différé du béton dans un pont ferroviaire mixte et précontraint

ABSTRACT A simply supported bridge deck of a new type with trough shaped cross section has been instrumented with strain gages and vibrating wire extensometers in June 2000 in order to assess its time-dependent behaviour. Additionally, creep and shrinkage tests on the C60 concrete used in this bridge deck are carried out in our laboratory. This paper reports on the comparison between creep and shrinkage measurements on the concrete samples and the predicted values by the more recent models. Then, bridge deck strain measurements are compared with predicted values by two pseudo—elastic analysis methods: the first one uses simply a variable modulus of elasticity whereas the second one applies the age adjusted effective modulus method.