Load-slip performance of Mass Timber Panel-Concrete (MTPC) composite connection with Self-tapping screws and insulation layer

The Mass Timber Panel-Concrete (MTPC) composite floor systems are often encountered in mass timber buildings. Such a floor system consists of a Mass Timber Panel (MTP) connected to a reinforced concrete slab with Self-Tapping Screw (STS) connector and a sound insulation layer in between. In this study three types of MTPs with normal weight concrete, three insulation thicknesses, two screw embedment lengths and two screw angles were tested to characterize connection stiffness and strength. The main goal of this connection test program was to provide preliminary test data to assist in the development of an analytical model to predict connection lateral stiffness and strength considering the insulation layer in the MTPC system. Test results showed that connections with screws at an insertion angle of 30 degrees had a larger stiffness and strength than connections with screws inserted at a 45 degrees angle. Stiffness appears to be more sensitive to the presence of an insulation layer compared to strength. Overall, 35-50% and 55-65% reduction of serviceability stiffness, and 5-15% and 22-34% reduction of strength were noticed for an insulation thickness of 5 mm and 15 mm, respectively. Screws in Cross Laminated Timber (CLT) showed higher strength while screws in Glue Laminated Timber (GLT) showed higher stiffness, but the difference is insignificant in all three MTP products with different failure modes. (C) 2019 Elsevier Ltd. All rights reserved.