Development of composite action in a new long-span timber composite floor: Full-scale experiment and analytical approach

Abstract

The mechanical performance of timber composite floor elements significantly depends on the composite action among different components. The composite action in conventional timber floors with a span limit of 8–9 m has been studied during the last two decades. For long-span timber composite floors with a span over 12 m, how to develop an efficient composite action is still an open question. In this study, the composite action in a long-span timber composite floor system was investigated. The floor system integrates LVL (Laminated Veneer Lumber) panels and GLT (Glued Laminated Timber) beams to form a continuous box girder structure. Various types of inclined screw connections combining LVL and GLT for a composite action were tested. One configuration was chosen to make the 12 m composite floors and four-point bending tests were conducted at different screw spacings. The degree of composite action was evaluated based on the observed overall bending stiffness and relative displacements between different components. The composite action in timber composite floors with concrete topping was also studied. An analytical approach based on Gamma method was adopted to estimate the effective bending stiffness of the composite floor. The findings in this study showed that bending stiffness over 26,000 × 109N·mm2 and composite action over 50 % can be achieved with a small number of screws. Reducing the screw spacing and adding concrete topping would further improve the overall stiffness. The predictions of the analytical model match well with the tested results for both the configurations with and without concrete topping.