The most overdesigned bench on campus!

This bench is a scaled-down model of the CLT-concrete-composite floor on which is sits. It was created as a student project before the Design Building was even built to explain the novel floor system used in this building.

In general terms, a wood-concrete-composite (WCC) floor system consists of a bottom layer (cross-laminated-timber, CLT, in this case), arranged in the direction of the span, which resists tension stresses. It also uses a concrete layer on top, which resists compression stresses, but also provides additional fire safety and a solid wear surface. Both of those layers are then structurally connected by a steel mesh (the “HBV” fastener) that has been glued into the wood layer and extends into the concrete layer, thereby creating the composite system. Between the two layers, a sheet of¬†insulation foam has also been added to improve sound performance between floors.

While the Design Building’s floors span up to 25 feet in some places, this bench mockup spans only eight feet. Also, the CLT slabs in the actual floors consist of five layers (instead of three), the insulation layer is 1″ thick (instead of 3/4″) and the concrete is 4″ thick (instead of 3″). Furthermore, in the actual floors, the HBV fasteners only extend into the top layer of the CLT slab, not below.

So, what is the benefit of such a system? By structurally connecting the concrete and wood layers, we are significantly improving both strength (how much more load the floor can carry) and stiffness (how much less bouncy the floor is). Feel free to jump on the bench and see how solid it feels.

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