Variability of charring along the wooden wall studs

The effect of timber densities on the charring of timber members insulated by heat-resistant mineral wool is described in this paper. Special attention is given to variability of charring along the stud. After the fire tests, the studs were saved in their entire length. Char layer was mechanically removed from the studs under investigation. Charred studs of timber frame walls were scanned three-dimensionally over the full length afterfull-scale fire tests. Densities were measured by X-ray and optical vibration scanner. Cross-section properties and densities of the studs were measured along the stud. Charring rate is not uniform along the full length of a single timber wall stud. This corresponds probably to the variation of density of wood. Adjusting the designmodel for charring of timber frame assemblies, as given in EN 1995-1-2, to allow for the influence of density may give an advantage for members with higher density. Medinių karkasinių sienų statramsčių apanglėjimo gylio kitimas Santrauka Straipsnyje analizuojama skirtingo medienos tankio, apsaugoto ugniai atsparia mineraline vata, įtaka apanglėjimo gyliui. Ypatingas dėmesys atkreiptas į skirtingą apanglėjimo gylį per visą statramsčio ilgį. Atlikus realių matmenų medinių karkasinių sienų ugnies poveikio eksperimentinį tyrimą, statramsčiai liko išsaugoti per visą ilgį. Nuo apanglėjusių statramsčių anglis mechaniniu būdu buvo nuvalyta, statramsčiai nuskenuoti trimačiu skeneriu, rentgenu buvo išmatuotas statramsčių tankis. Apanglėjimo gylis per visą statramsčio ilgį buvo skirtingas. Tikėtina, kad tai lėmė skirtingas medienos tankis. Todėl skirtingo medienos tankio vertinimas, tobulinant EN 1995-1-2 reglamentuojamą medienos apanglėjimo skaičiavimo modelį, galėtų suteikti pranašumų didesnio tankio elementams. First Published Online: 16 May 2013 Reikšminiai žodžiai: apanglėjimo greitis, medinio karkaso surinkimas, apanglėjimo gylis, tankio įtak

Experimental Study of the Charring of I-Joists and Recession of Combustible Insulation in Light Timber Frame Assemblies with Comparison to Eurocode 5

Design models are commonly used in fire safety design of light timber frame assemblies. Parameters for use in the models are available for rectangular members with mineral wool, wood fibre or cellulose insulation and for assemblies with I-joists and mineral wool. For assemblies where I-joists and combustible insulations are combined, design parameters are missing. Five fire experiments with two Ijoist types and four combustible insulation products have been conducted. The aim was to study charring of I-joist flanges and recession rates of combustible insulations and in addition, to compare their behaviour to the new and existing models of Eurocode 5. Charring rates for the flanges were 0.40–0.76 mm/min and 0.54–1.72 mm/min for the protected and post-protected phase, respectively. Rates decreased with increasing flange size. Charring rates for flanges of solid wood and LVL were comparable. The results show that lateral charring of I-joist flanges can be significant in the protected phase. The tested insulation products showed a lower recession rate than values reported for glass wool insulation, with a more pronounced difference for wood fibre and cellulose insulations. The low recession rates compared to previously reported generic values can possibly be explained by better product-specific properties, negligible shrinking and slightly different test set-up. The insulation stayed well in place after gypsum board fall-off and best-practice for keeping the insulation in place is given. The results, completed with future loaded full-scale tests, can give basis for further development of design models for assemblies with I-joists and combustible insulations.publishedVersio

Fire Safety of CLT Buildings with Exposed Wooden Surfaces

An increasing number of tall buildings made of CLT have been built in recent years. Current architectural trends involve having visible timber surfaces in these tall CLT structures. This results in new fire safety challenges, especially because fire service interference is increasingly difficult for increasingly tall buildings.   Recently, a number of research projects involving large scale compartment fire testing studied the development of fires in (1) compartments with a fully encapsulated CLT structure and (2) compartments with exposed CLT surfaces. The studies have shown that sufficient gypsum board protection can avoid the involvement of CLT in a fire. However, fall-off of the base layer of gypsum boards during can result in continuous fires that do not extinguish without fire surface interference, as during fall-off large areas of initially protected timber surfaces start to contribute as fuel to the fire.   If CLT is exposed to a fire, fire induced delamination of CLT (also lamella fall-off or char fall-off) could occur due to weakening of bond lines within the CLT. During fire induced delamination the exposed lamella falls from the CLT and a new relatively cold timber surface becomes exposed to potentially high temperatures, which effectively makes additional fuel suddenly available to a fire.   Very recent studies involved the development of CLT products that are not subject to delamination. The studies indicate that the use of (a) sufficient fire protection, (b) CLT products with thermally resistant adhesives and (c) a limit regarding the surface area of CLT that can be exposed, result in fires that decay and eventually self-extinguish. This paper reviews the studies and includes a summary of conclusions

Fire Safety of CLT Buildings with Exposed Wooden Surfaces

An increasing number of tall buildings made of CLT have been built in recent years. Current architectural trends involve having visible timber surfaces in these tall CLT structures. This results in new fire safety challenges, especially because fire service interference is increasingly difficult for increasingly tall buildings.   Recently, a number of research projects involving large scale compartment fire testing studied the development of fires in (1) compartments with a fully encapsulated CLT structure and (2) compartments with exposed CLT surfaces. The studies have shown that sufficient gypsum board protection can avoid the involvement of CLT in a fire. However, fall-off of the base layer of gypsum boards during can result in continuous fires that do not extinguish without fire surface interference, as during fall-off large areas of initially protected timber surfaces start to contribute as fuel to the fire.   If CLT is exposed to a fire, fire induced delamination of CLT (also lamella fall-off or char fall-off) could occur due to weakening of bond lines within the CLT. During fire induced delamination the exposed lamella falls from the CLT and a new relatively cold timber surface becomes exposed to potentially high temperatures, which effectively makes additional fuel suddenly available to a fire.   Very recent studies involved the development of CLT products that are not subject to delamination. The studies indicate that the use of (a) sufficient fire protection, (b) CLT products with thermally resistant adhesives and (c) a limit regarding the surface area of CLT that can be exposed, result in fires that decay and eventually self-extinguish. This paper reviews the studies and includes a summary of conclusions