Non-linear analysis of a stress-laminated-timber bridge loaded to failure

The general assumption in stress-laminated-timber (SLT) bridge design is that the structural response is linear both in the serviceability limit state (SLS) and in the ultimate limit state (ULS). However, this has been shown not to be the case according to a full-scale test performed in Sweden where the SLT deck was subjected to a failure load. When an SLT deck is loaded to failure, non-linear behaviour must be considered when a structure of this kind is analysed. Both horizontal and vertical slip occur in the interlaminar interface between the stressed glulam laminations. This behaviour does not occur in a solid timber plate. Once slip has occurred, the stresses are redistributed between the laminations. Interlaminar slip is of great importance and is affected by several factors such as the pre-stress level, surface roughness and surface moisture content. A rectangular SLT deck, 5.00 × 7.98 × 0.27 m 3 (length, width and thickness), with two patch loads positioned close to the edge, was tested. The deflection values for both ultimate and non-destructive loads were compared with finite element (FE) models of the SLT deck in order to evaluate the behaviour of the deck. The results from the experiments were compared with both linear and non-linear FE models.