Effect of vertical interlaminar shear slip and butt joints in narrow stress-laminated-timber bridge decks

• Interlaminar slip between beams in stress-laminated-timber decks was investigated.
• Non-linear FE analyses are compared with the test results.
• The relation between interlaminar slip and the normal stress magnitude is shown.
• A stiffness reduction due to butt joints was observed.

Interlaminar slip occurs in stress-laminated-timber (SLT) decks subjected to concentrated loads, such as vehicles. Butt joints in SLT decks can be regarded as local discontinuities with increased load transfer resulting in increased frictional forces. Multiple tests were performed with different combinations of pre-stress level, number of loads, span-to-depth ratio, beam width and butt-joint configurations. The results of the tests have been analysed and compared with non-linear finite element analyses using solid elements and contact properties. The experimental results and the analysis showed that, in the case of a high span-to-depth ratio in the deck and without butt joints, there is little or no interlaminar slip. Test elements without butt joints showed little slip at pre-stress levels of 300 kPa or higher. A significant reduction in post-slip stiffness was observed for the test elements with butt joints.