Prestressed timber bridges : simulations and experiments of slip

Martinsons Träbroar produces currently around 40-50 timber bridges each year where more than half of them are transversally prestressed (stress laminated) decks. A semi-empirical beam theory model is and has been used to determine the height of the decks and the prestress levels. An alternative modelling technique using finite element methods is described in this paper. The purpose for investigating this alternative method is to increase the understanding of behaviour and load bearing capacity of prestressed timber decks. Also to increase the accuracy and efficiency of the design process.The alternative simulation model is an elastic-plastic three-dimensional finite element model. It handles all stress components and is well suited for stress design of timber bridges. The plastic material behaviour of the model makes it possible to model slip between glulam beams in a bridge deck of a prestressed timber bridge. Examples of simulation and experimental results for bridge decks are shown. The results are especially interesting when judging the behaviour of bridge decks for low levels of prestress. An important question is how these results can be interpreted when it comes to design of timber bridges and also the long-time behaviour of real timber bridges.Godkänd; 2010; 20110315 (ysko