Fire Performance of Timber-Concrete Composite (TCC) Systems in Mass Timber Buildings

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In a new era full of possibilities for manufacturing large timber sections made of engineered wood, i.e., glued-laminated timber (glulam), cross-laminated timber (CLT) and nailed-laminated timber (NLT) sections, strength and structural integrity of such sections can be retained for much longer time in fire. As a result, several tall buildings made primarily of timber are increasingly being constructed worldwide. Floor systems in such buildings can even be made stronger and span longer distances to allow designers greater versatility in terms of floor plan and promote for open concept design in modern buildings by adding a top layer made of concrete that allows the formation of Timber-Concrete Composite (TCC) floor systems with the use of sufficient shear connections. In this composite system, the advantageous mechanical properties of both materials are efficiently utilized and thus, several advantages can be achieved for a more robust floor system, if compared to timber floors such as those made solely of CLT or NLT panels. Among the several advantages of utilizing TCC floor systems are greater strength, durability, and much improved acoustics and vibration performance characteristics. Unfortunately, experimental work on TCC systems in fire conditions is not as extensive as at ambient temperature, and thus one very important area that warrants further investigation is the behaviour of TCC floor systems in fire conditions with focus on certain aspects. For instance, most previous experimental studies on TCC floor systems were of small size, small number and/or representing one-way floor assemblies; whereas in the proposed research program, twenty-four (24) large-scale two-way TCC slab-type floor assemblies utilizing CLT and NLT panels will be examined in fire conditions. Also, it is very rare to find research studies that address the effect of inter-panels joint connections on the structural fire behaviour of TCC floor systems, and thus those test assemblies with CLT panels will include spline panel-to-panel connections. In addition, the use of a supporting framing system made of glulam beams along the perimeter of the TCC floor slab to enhance the membrane action of the concrete slabs in fire is something that has never been presented in the available literature so far. Therefore, it is believed that the proposed research program will lead to: development of new and reliable experimental data and possible implementation of design models for TCC slab-type floor systems in fire conditions in the future version of CSA O86 standard (scientific impact); development of FE models that can simulate the actual behaviour of those TCC floor assemblies with the selected shear connections in fire conditions (technological impact); indirectly support the Canadian wood industry through the development of new design models (economic impact); and allow more robust, sustainable material-made, and fire safe mass timber buildings for Canadians (social impact).