Innovative nail laminated timber-concrete composite floor deck system

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A substantial amount of research has been conducted over the past 10 years on the development of composite timber floor systems consisting of a concrete slab and timber beams that are connected using shear connectors. A slightly different version of this type of composite systems is to use a cross laminated timber (CLT) or structural composite lumber (SCL) deck inserted between the beams and concrete slab. This modified concept originated from the profiled steel-concrete slab composite system which is widely used in long-span floor construction. The wood deck serves as formwork for the concrete slab and reduces the thickness of the concrete slab. The economics of such a 2-layer deck system is prohibitive due to the relatively high cost of CLT and SCL. ******In this research a more cost-effective 2-layer deck system consisting of a profiled nail laminated timber (NLT) panel and a reinforced concrete slab will be developed. The profiled NLT panel is fabricated by nailing 2 by 3 (38mm x 63mm) lumber with deeper lumber. Structurally, the profiled NLT can provide a shear key to enhance composite action with the concrete slab, especially in the transverse direction. ******From the production perspective, this deck system can be produced using simple tools, such as nail guns and clamps, and an under-utilized resource of 2x3 lumber. The first phase of the research will develop the most optimum product format and construction details. The basic components of lumber and concrete will consist of relatively low-grade materials. Two PhD students will work on this product development phase in the first 3 years. At the end of year 3, it is expected that the following parameters will be resolved: 1. Suitable nailing patterns for the NLT; 2. Optimum NLT profile geometry consisting of alternating 2x3 and deeper lumber; 3. Suitable mechanical shear connectors between concrete and profile NLT using light fasteners; 4. Suitable details for connecting adjacent decking panels; 5. Maximum floor span potential. ******In the second phase, which will be conducted in years 4 and 5, two issues will be investigated. The first one will be the connection details between the 2-layer deck system and the supporting timber or steel beams. Focus will be on the use of heavy duty fasteners, such as steel dowels. The second issue to be investigated will be the vibrational performance of the 2-layer deck system on its own and that of the complete floor system consisting the 2-layer deck and supporting beams. It is important to study vibrational performance because it is well known that for long-span floor systems, vibration serviceability likely governs the structural design. This phase will be conducted by 2 MSc students. If the results from this project show potential commercial viability for the deck system, a more comprehensive project, which will develop more refined fabrication procedure and examine other performance issues such as fire and acoustics, will be pursued.