In recent years, cross-laminated timber (CLT) has been increasingly used as a sustainable alternative to conventional construction materials, particularly for floor applications. This includes point-supported flat-slabs, also called post+plank, such as in the 18-storey Tall Wood House in Vancouver. The crosswise orientation of CLT layers and its inherent mechanical properties are better utilized when adopted as point-supported flat-slabs. In this system, the CLT panels are supported directly by columns, without the need for beams and their connections, reducing installation cost and time, allowing the layout to be readily changed by altering wall locations, and increasing the free floor height.
One relevant material strength property in these applications is the CLT punching shear strength, which refers to its ability to resist concentrated loads or "punching" through the material. CLT punching shear strength is directly related to the lamella rolling shear strength, which can be estimated through 4-point bending, 3-point bending, or inclined in-plane shear tests. Previous research has shown that CLT rolling shear strength increases under punching shear due to the confinement effect of lamellas from adjacent layers (clamping effect) and the presence of compression forces perpendicular to grain.
The current North American and European do not provide any direct guidance on the design of point-supported CLT floors. To address this need, a project is being conducted in collaboration between Fast + Epp, Concept Lab and the University of Northern British Columbia with the objective to develop design guidance for point supported CLT floors. To achieve this objective, an experimental punching shear testing program is underway.