A Dovetail Notched Connection for Cross-Laminated-Timber-Concrete Composite Slabs: Experimental Investigation

This paper presents an experimental study on the behaviour of notched connectors with a dovetail shape that is able to limit the uplift without the need for steel screws. A series of three symmetrical push-out tests were performed on large-scale specimens in order to determine the shear resistance, the stiffness, the deformation capacity and the failure mode of the connector. The test results showed high shear resistance and stiffness of the connectors. However, the ductility of the connectors was low, as the failure mode was governed by the shear failure of the cross layer of the CLT. In addition, the global behaviour of the CLT-concrete slab with the dovetail notched connectors was assessed by a series of two full-scale flexural tests on slab specimens under a positive bending moment. It was shown in the test results that the design of the composite slab is not limited by the flexural bearing capacity as a high value of the maximum bending moment was obtained in the tests. It is instead governed by the deflection of the composite slab. The delay in the tests caused by the Covid crisis has moreover set in evidence the importance of the shrinkage of concrete in the total deflection. Besides, a modified gamma method was used to estimate the mid-span deflections and compared with the ones obtained from the flexural tests. The results showed a good agreement, validating the use of the modified gamma method for the estimation of the stiffness of the CLT-concrete slab with Dovetail notched connection. In addition, a beam grid model was also employed in order to take into account the stiffness of the slab in the transversal direction.