Fire tests on glued-laminated timber beams with specific local material properties

Abstract

The fire resistance of glued-laminated timber (glulam) beams is usually determined by calculation models or by tests. The evaluation of the fire resistance tests is accompanied by an uncertainty with regard to the timber material properties, which is, however, important to know when comparing the test results to the effective cross-section method according to EN 1995-1-2. The present paper presents therefore for the first time the results of six fire resistance tests with glulam beams with specific local mechanical material properties, such as exact position and dimension of knots, weak sections and finger joints, densities and strength properties of small cells. The tested glulam beams had an approximate height of 250 mm and reached a fire resistance of up to 68 min. The performed fire tests allowed the determination of the zero-strength layer with a higher certainty than investigations performed in the past. Additionally, reference tests at ambient temperature were considered in the evaluation. The determined zero-strength layer was in the range of 7 mm, as given in the current version of EN 1995-1-2 for beams in bending.