Fire Performance of Timber Connections, Part 1: Fire Resistance Tests on Bolted Wood-Steel-Wood and Steel-Wood-Steel Connections

Abstract

This paper presents the results of a series of fire-resistance tests on bolted wood-steel-wood (WSW) connections and bolted steel-wood-steel (SWS) connections. In total, 16 WSW specimens and 6 SWS specimens were tested in accordance with the provisions of CAN/ULC-S101. All the specimens were subjected to a constant tensile load parallel to grain during the tests. The effects of load level, wood thickness, fastener diameter, number of fasteners, edge distance and protection were studied. The test results show that the fire-resistance ratings of all the tested WSW connections without protection were less than 45 minutes (a target rating for Canadian code compliance) and the fire-resistance ratings of all the tested SWS connections without protection were less than 25 minutes. Specimens with thicker wood side members were found to exhibit better fire resistances. Decreasing the load ratio increased the fire resistance. The test results on protected specimens show that the protection provided by a single-layer of 15.9 mm type X gypsum board increased the fire resistance by more than 30 minutes, whereas a double-layer of 12.7 mm Douglas fir plywood increased the fire resistance by 15 minutes. Furthermore, this research has generated necessary data and knowledge for the validation of a numerical heat transfer model and an analytical structural model.