Investigation of the high temperature performance of a polyurethane adhesive used for structural wood composites

Abstract Fire resistance and thermal stability are among the most important criteria for engineered wood product applications in mass-timber buildings. This project investigated the shear strength of mass timber adhesively bonded joints at high temperatures. Shear tests were conduct on specimens made of Douglas-Fir Glued-laminated Timber and a steel plate glued in with a one component polyurethane adhesive. The results indicate that the shear strength of the adhesive was affected by temperature. Between 20°C and 75°C, the shear strength of the joints decreased with increasing temperature. Above 75°C, the strength of the adhesive became constant at less than half that at 20°C. Therefore, it is recommended that if the polyurethane adhesive is used for glulam-steel plate structures above 75°C, the design strength should be only about 40% of the design strength at room temperature.