ForestValue - FIRENWOOD; Improved fire design of engineered wood systems in buildings

There is a growing use of wood in construction, which substantially contributes to developing a more sustainable construction sector. Although fire safety is considered important, the adhesive properties of glued products at elevated temperatures and in fire conditions are not fully understood. FIRENWOOD aims to fill knowledge gaps regarding the fire-safe use of engineered wood systems, focusing on structural joints and adhesives in cross-laminated timber (CLT), glued-laminated timber (GLT), glued-in rods, and wood-based I-joists. Benefiting from the close collaboration between adhesive manufacturers, engineering wood providers, research institutes, and universities, FIRENWOOD delivered more than 2000 experiments using eighteen selected adhesives covering all common adhesive families. Many adhesives were studied using different experimental methods and at different scales. To our knowledge, such a comprehensive experimental campaign has never been performed and reported openly. Furthermore, extensive efforts were made to make sure a direct comparison could be made from different experiments. The vast amount of high-quality experimental data enabled us to understand better the behaviour of bond lines of engineered wood in fires. Several fire design models for CLT, GLT, glued-in rods, and I-joists were proposed, some of which have been included in the new draft of European standards for the design of timber structures (CEN/TC 250/SC 5 - Eurocode 5). New adhesive classification methods using only small-scale apparatus were also proposed in FIRENWOOD, which will be considered by the European Committee for Standardisation (CEN/TC 193/SC 1) in developing future European standards for wood adhesives. With the developed fire design models and classification methods from FIRENWOOD, the costs and difficulties of establishing engineered wood constructions, especially with taller buildings, can be significantly reduced without sacrificing fire safety. Hopefully, the outcome of FIRENWOOD will facilitate increased production and demand of wood and glued elements, allowing for broader use of the raw material and supporting regional wood processing companies.

The main results from FIRENWOOD are 1) the common understanding and agreement of behaviour of bond lines of engineered wood in fires; 2) improved fire design models for engineered wood (I-joists, glued laminated timber, cross-laminated timber, glued-in rods) taking the adhesive behaviour into account; 3) simple assessment methods for adhesives according to their fire behaviour. FIRENWOOD results have been mainly presented to two European standardisation groups: CEN TC193 SC1 Adhesives for wood and derived timber products, WG13 - Fire behaviour and CEN TC250 SC5 Structural Eurocodes – Eurocode 5:Design of Timber Structures, WG4 - Fire. The new version of CEN TC250 SC5 “Eurocode 5” has been greatly influenced by FIRENWOOD by including design models proposed by FIRENWOOD. Project partners have also been provided inputs to European standardisation committees such as TC 127 - Fire safety in buildings and TC 124 - Timber structures. The knowledge, models, and methods developed in FIRENWOOD will make the application and use of innovative wood systems in construction more available and economical. This effect will be even stronger by the potential adoption of pre-accepted solutions based on the gained knowledge. Smoother fire design and pre-accepted solutions are highly requested by suppliers of engineered wood systems and will strengthen the economic and competitive potential for the wood-based construction industry compared to traditional solutions of concrete and steel.

The requirements for more environmentally friendly building materials in constructions are growing internationally. Wood is traditionally appreciated as a construction material due to its flexibility, strength, environmental friendliness, esthetical nature and good fire technical properties. FIRENWOOD will fill knowledge gaps regarding fire safe use of engineered wood systems, with focus on structural joints and adhesives in CLT, GLT and wood-based I-joists, and develop validated fire design models for these systems and classification methods for adhesives. A key point is to investigate the behaviour of adhesives used in structural applications, as many of these innovative systems utilise different adhesives. The societal perception of fire safety of timber buildings is influenced by the media, which is addressing the topic with controversy, also tending to be pessimistic, and the FIRENWOOD project aims to facilitate change in a general negative public opinion of timber structures in fire. Internasjonale krav om mer miljøvennlige byggematerialer i konstruksjoner øker. Tre er tradisjonelt verdsatt som byggemateriale på grunn av sin miljøvennlighet, fleksibilitet, styrke, estetikk og gode branntekniske egenskaper. FIRENWOOD vil fylle kunnskapshull med hensyn til brannsikker bruk av konstruerte tresystemer, med fokus på skjøter og lim i krysslaminert massivtre, limtre og trebaserte I-bjelker, og validerte branndesignmodeller for disse systemene samt klassifiseringsmetoder for lim vil bli utviklet. Et sentralt punkt er å undersøke egenskapene til lim brukt i konstruksjonselementer, da mange av disse innovative systemene bruker forskjellige lim. Samfunnets oppfatning av brannsikkerheten til bygninger i massivtre påvirkes av media, som tenderer å være pessimistisk. FIRENWOOD vil skape kunnskapsgrunnlag for å endre den generelt negative oppfatningen av massivtrekonstruksjoner i brann.