OPEN ACCESS
The main objective of this paper is to identify different analytical methods which permit the calcula-tion of the stress level in wooden simply supported beams, due to mechanical and thermal loading conditions. Two different wood species, with different cross-sections, will be presented. The fire resistance, the charring depth layer and the charring rate will be determined using the finite element method with Ansys® program. To characterize the stress state in wooden beams, all elements are subjected to mechanical load considering the reduction of the cross-section, influenced by thermal action. Another purpose of this work is to identify the ultimate safe load-bearing capacity in wooden beams, subjected to uniform load simultaneously with the thermal effect. All numerical results per-mit the specification of simple design calculation methods, simplifying the verification of the fire safety of wooden beams.
charring depth, fi re, load-bearing capacity, uniform load, wooden beam
[1] White, R.H. & Dietenberger, M.A., Fire safety (Chapter 17). Wood Handbook: Wood as an Engineering Material, Forest Products Laboratory, USDA Forest Service, 1999.
[2] Poon, L. & England, J.P., Literature Review on the Contribution of Fire Resistant Timber Construction to Heat Release Rate – Timber Development Association, Warrington Fire Research Aust. Pty. Ltd., Project No.20633, version 2b, pp. 1–78, 2003.
[3] Janssens, M.L., Modeling of the thermal degradation of structural wood mem-bers exposed to fire. Fire and Materials, 28, pp. 199–207, 2004. doi: http://dx.doi. org/10.1002/fam.848
[4] Schaffer, E.L., Charring Rate of Selected Woods Transverse to Grain. Research paper FPL 69 Forest Products Laboratory: Madison (WI), 1967.
[5] White, R.H., Charring Rates of Different Wood Species. PhD dissertation, Madison University of Wisconsin, Madison (WI), 1988.
[6] White, R.H., Erik, V. & Nordheim, E.V., Charring rate of wood for ASTM E119 expo-sure. Fire Technol, 28(1), pp. 5–30, 1992. doi: http://dx.doi.org/10.1007/BF01858049
[7] Konig, J. & Walleij, L., One-Dimensional Charring of Timber Exposed to Standard and Parametric Fires in Initially Unprotected and Postprotection Situations. Swed Inst Wood Technol Res, 1999.
[8] Gardner W.D. & Syme, D.R. Charring of Glued-Laminated Beams of Eight Australian-Grown Timber Species and the Effect of 13 mm Gypsum Plasterboard Protection on their Charring. N.S.W. Technical report no.5, Sydney, 1991.
[9] Collier, P.C.R., Charring Rates of Timber, Study report, Branz: New Zealand, 1992.
[10] Pun, C.Y., Seng, H.K., Midon, M.S. & Malik, A.R., Timber Design Handbook. FRIM, Malayan Forest Records no.42, 1997.
[11] Cachim, P.B. & Franssen, J.M., Assessment of Eurocode 5 charring rate calculation methods. Fire Technology, 46, pp. 169–181, 2010. doi: http://dx.doi.org/10.1007/ s10694-009-0092-x
[12] Fonseca, E.M.M. & Barreira, L., Charring rate determination of wood pine profiles submitted to high temperatures. Third International Conference on Safety and Security Engineering, Vol. 108, eds M. Guarascio, C.A. Brebbia, F. Garzia, WIT Press: Italy, pp. 449–457, 2009.
[13] Fonseca, E.M.M. & Barreira, L.M.S., Metodo experimental para determinacao da espessura carbonizada na madeira quando submetida a altas temperaturas. Revista Portuguesa de Engenharia de Estruturas RPEE, 7, pp. 33–40, 2010.
[14] Fonseca, E.M.M. & Barreira, L., High temperatures in parallel or perpendicular wood grain direction: a numerical and experimental study. WIT Press, Fourth International Conference on Safety and Security Engineering IV, eds. M. Guarascio, G. Reniers, C.A. Brebbia, F. Garzia, Belgium, 117, pp. 171–183, 2011.
[15] Fonseca, E.M.M. & Barreira, L., Experimental and numerical method for determining wood char-layer at high temperatures due an anaerobic heating. International Journal of Safety and Security Engineering, 1(1), pp. 65–76, 2011. doi: http://dx.doi.org/10.2495/ SAFE-V1-N1-65-76
[16] Gandhi, PD. & Backstrom, R., Thermal and Mechanical Finite element modelling of Wood-Floor Assemblies Subjected to Furnace Exposure. Project number: 07CA42520, Underwriters Laboratoires, USA, 2008.
[17] EN 1991-1-2:2002. Eurocode 1: Actions on Structures – Part 1–2: General actions – Actions on Structures Exposed to Fire, CEN, 2002.
[18] EN 1995-1-2:2004. Eurocode 5: Design of timber structures, Part 1–2: General-Structural fire design, CEN, 2004.
[19] Winady, J. & Rowell, R., Chapter 11. Chemistry of Wood Strength. Handbook of Wood Chemistry and Wood Composites, CRC Press LLC, pp. 303–347, 2005.
[20] Green, D.W., Winandy, J.E. & Kretschmann, D.E., Mechanical Properties of Wood, ch04, Wood Handbook Wood as an Engineering Material, Forest Products Laboratory USDA Forest Service: Madison, Wisconsin, 1999.