On the use of springs in stress-laminated wood decks

Abstract

Transverse post-tensioning forces, essential for the structural integrity of stress-laminated wood decks, are subject to losses because of the time- and stress-dependent shrinkage of wood. Through physical testing conducted over the last 20 years, it has been found by a number of researchers that the prestress losses in these structures can be minimized by reducing the stiffness of the post-tensioning system and also by incorporating mechanical springs between the deck and the post-tensioning system. From this observation, it has been generally concluded by the investigators that the incorporation of springs in stress-laminated wood decks is equivalent to reducing the stiffness of the post-tensioning system. In this note, it is argued that this assumed equivalence is not true, but that the springs are nevertheless effective in reducing prestress losses in stress-laminated wood decks. Key words: post-tensioning, prestress losses, stress-laminated wood deck, wood bridge, wood deck.