Fire resistance of Laminated Veneer Lumber (LVL) and Cross-Laminated Timber (XLAM) elementsud

摘要

Engineering design of timber structures in fire conditions is crucial to ensure high safety levels. Wood is subjected to degradation under fire exposure therefore its thermaludand mechanical behaviours change. Timber design must take the decrease of timber performance into account to calculate structural elements that can carry external loadsudalso if exposed to high temperatures. Analytical and numerical approaches can be adopted in fire design practice.udThis research investigates the fire behaviour of laminated veneer lumber elements and cross-laminated timber panels. The study focused on some research questions regarding the fire resistance of unprotected and protected timber structural elements, the possibility to predict accurately the fire behaviour of timber elements through numericaludmodelling, and the accuracy of analytical estimations of fire resistance using simplified design methods.udExperimental tests of small and large specimens exposed to fire on one or more sides and subjected to different types and levels of load were performed. The results highlight the good performance of timber structural elements in fire conditions. The collected data were used to validate two- and three-dimensional models implemented in the general purpose finite element code Abaqus. Thermal and mechanical analyses were carried out to estimate the temperature distribution within unprotected and protected cross-sections of different sizes, the fire resistance and the displacement of timber elements loaded in-plane and out-of-plane. Further, parametric studies assuming different timber properties-temperature relationships were also performed. The proposed numerical modelling can be used to investigate the fire behaviour of timber members made of other wood-based products and subjected to different loads and fire conditions. Experimental and numerical results were compared with analytical predictions obtained by using simplified design methods proposed by current codes of practice and recent research proposals. Numerical and analytical methods provide overall acceptable estimations of fire behaviour of timber members, especially considering the high variability that characterizes the wood material and the experimental tests, in particular the fire tests.ud