Fire Experimental Testing of STS-Reinforced Glulam Beam-End Connections with Metal Connectors’ Wood Protection

This paper presents the results of an experimental study on the fire performance of minimally fire-protected wood-steel-wood (WSW) beam connections strengthened with self-tapping screws (STS). Two full-size fire endurance tests were conducted on glulam beam-end connections subjected to shear and bending moment. Two connection configurations were investigated, each utilizing four structural steel bolts arranged in two different patterns. The beam-end connections were reinforced perpendicular to the wood grain using six STS and exposed to elevated temperatures that followed the CAN/ULC S101-19 standard fire time-temperature curve while subjected to a load ratio equivalent to 60% of the maximum design moment of the weakest unreinforced connection configuration. The test results show that the failure time of both connection configurations conveniently exceeded 50 min, which surpassed the 45-min minimum fire resistance rating required by applicable building codes. The connection with the first bolt pattern, in which two rows of bolts were symmetrically positioned near the top and bottom sides of the beam section, performed better than that with the second pattern, in which the bottom row of bolts was raised to the mid-height of the beam section, and had a failure time surpassing 60 min under standard fire exposure. Most importantly, reinforcing the connections with STS prevented splitting or row shear failures, which are frequently encountered in unreinforced WSW connections.