Bending stiffness prediction to mass timber panel-concrete composite floors with notched connections

Abstract

Mass timber panel-concrete composite floors consist of bottom timber panels, a top concrete layer, and a connection system in between. Notched connections made by filling concrete into the grooves cut on timber are one of the most structurally effective and cost-saving solutions to connect concrete topping to mass timber panels. However, the notched connections are not standardized due to various shapes of grooves and reinforcing techniques, and design guidelines are inadequate in terms of effective measures to achieve high composite efficiencies in notch-connected composite floors. This study developed an empirical formula to determine the shear stiffness of notched connections based on numerical modeling. The proposed formula was verified by comparing the predicted floor bending stiffness using the discrete bond composite beam model with the test results. A parametric study was then carried out to study the effects of geometry factors, including notch depth, timber shear length, number of notches, and thickness of concrete, on the overall bending stiffness of the composite floor. It has been found that the maximum composite efficiency in a mass timber panel-concrete composite floor can be achieved through optimizing the number, size, and locations of notches. The analytical and numerical investigations on the composite floors also demonstrate that in a certain range the thickness ratio between concrete and timber has little impact on the composite floor bending stiffness.