Efficiency of closed stiffener orthotropic deck panels for railway bridges

Abstract

Closed stiffener orthotropic decks can be advantageous for ballasted or non-ballasted railway bridges. This has been achieved successfully on a number of tied arch railway bridges for the high-speed railway network in Belgium. In these bridges, the orthotropic plate contributes to both the deck plate action and the main load carrying system as the horizontal lower chord or arch tie. Although the basic structural action is comparable to that of road bridges, specific differences exist. These differences, which originate from a substantial discrepancy of the load transfer, are addressed in this paper. Railway loads considerably exceed applicable loads for road bridges, which result in significantly larger rib and floor beam dimensions. This has a significant impact on the transverse load spreading in the plate and on the moment redistribution due to floor beam flexibility. Load spreading describes the phenomenon in which a concentrated load is spread throughout a continuous medium. For typical railway bridge deck dimensions, the load spreading is nearly negligible. This mechanism is demonstrated in the paper. On the other hand, the axle loads are spread over a large area, reducing the contact pressure at the deck plate. Consequently, the potential for fatigue at the stiffener to deck plate joint is also reduced. In addition, the ballast layer bridges the plate areas between stiffener webs reducing deck plate stresses even further. This has serious consequences on acceptable deck plate dimensions, which differ substantially from the recommended values for road bridges. Therefore a different set of basic input data is considered for orthotropic decks of railway bridges, leading to a more efficient use of steel. All conclusions and recommendations presented in this paper are based on numerical Finite Element simulations and strain gauge measurements on a number of bridges.