Fire Performance of Connections in Laminated Veneer Lumber

Abstract

The embedment strength of timber with respect to exposure temperature has not been widely studied. Some studies have suggested that the timber totally loses its embedment strength when the timber temperature reaches 300℃. This research concentrates on the embedment strength study of Laminated Veneer Lumber (LVL) timber product exposed to elevated temperatures up to 250℃ using singly bolted connections. Experiments showed that the embedment strength of LVL decreased at a constant rate from 0.08 kN/mm² to 0.025 kN/mm² once the bolt temperature increased from ambient conditions. The embedment strength was then assumed to remain at strength of 0.025 kN/mm² as the bolt temperature continues to increase from 120℃. The difference between the estimated failure load based on Johansen's Equations and the experimental failure load for the connections tested under fire conditions was less than 30%. The estimation was based on bolt strength reduction using NZS 3404, the experimental charring rate and the experimental embedment strength. The predicted failure mode agreed with experimental for all types of connection.