SR29 Protected nailed gusset connections for glulam members (1990)

The fire performance of heavy glued laminated (glulam) timber members based on the sacrificial method of char is widely accepted. The performance of their mechanical connectors, possibly the weakest link, is frequently overlooked.

This report describes the experimental testing of six full-size nailed moment-resisting gusset connections between glulam timber members when subjected to the 60 minutes standard time temperature conditions. The parameters examined included different gusset types, different protection methods, beams of two depths and two levels of applied load.

The results of these tests indicated that protected nailed plywood or steel gusset connections can achieve a 60-minute fire resistance rating (FRR). Protection using two layers of a gypsum-based control board proved to be more than adequate, with a single layer achieving the 60-minute FRR. The degree of protection offered by an intumescent coating on the steel gussets was inconclusive.

This report also describes the experimental testing of four unloaded gusseted glulam specimens protected with a single layer of the control board subjected to the 60-minute standard time temperature conditions. These tests were carried out in a pilot furnace to determine the time temperature characteristics of the components beneath the protection to enable a comparative test method to be developed.