Dimensional behavior of nail-laminated timber-concrete composite caused by changes in ambient air, and correlation among temperature, relative humidity, and strain

A timber-concrete composite (TCC) slab composed of nail-laminated timber (NLT) and topping concrete (TC) was developed for flooring applications. The NLT was laminated alternately with lumber and plywood. To investigate the nonstructural dimensional behavior of the TCC slab, the temperature, relative humidity (RH), and dimensional changes of the slab exposed to outdoor air were monitored for 205 days. Temperature change was transmitted directly to both components, and RH change was transmitted gradually to the NLT. Concrete pouring caused a sharp increase in NLT width, which was the laminating direction of the nails. This resulted from swelling of the wood owing to the moisture in the concrete mixture and loosening of the nail lamination. The member composition for the nail-laminating system, fastener type, and concrete volume help to secure the dimensional stability of the NLT. Cracks i…