Fire Safety of Glued-Laminated Timber Beams in Bending

Abstract

Design models for timber structures with fire-resistance requirements usually take into account the loss in cross section due to charring and the temperature-dependent reduction in strength and stiffness of the residual cross section. Standards for glued timber elements like glued-laminated timber beams have assumed that structural adhesives do not influence the fire resistance, but further specifications of adequate adhesive requirements are missing. Investigations were therefore conducted to determine the influence of different adhesives on the load-carrying behavior of glued-laminated timber beams in fire. Large-scale fire-resistance tests in combination with extensive finite-element analyses showed that a modification of the zero-strength layer thickness of d0=7 mm currently used in a standard design code should be discussed for glued-laminated timber loaded in bending in a future release of this design code. An increase of the zero-strength layer d0 considering the finger-joint strength depending on the approved structural adhesive is not needed.