Structural Safety in Wooden Beams Under Thermal and Mechanical Loading Conditions

Structural Safety in Wooden Beams Under Thermal and Mechanical Loading Conditions

E.M.M. Fonseca D.C.S. Coelho L.M.S. Barreira 

Department of Applied Mechanics, Polytechnic Institute of Bragança, Portugal

Page: 
242-255
|
DOI: 
https://doi.org/10.2495/SAFE-V2-N3-242-255
Received: 
N/A
| |
Accepted: 
N/A
| | Citation

OPEN ACCESS

Abstract: 

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.

Keywords: 

charring depth, fi re, load-bearing capacity, uniform load, wooden beam

  References

[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.