Flexural Strengthening of Structural Timber in the 21st Century: A State of the Art Review

Abstract:

The use of structural timber has never caught on in Malaysia despite the fact that the country is a major exporter of many commercially important hardwoods such as dark red meranti, kapur and keruing, among others. Chief concern among structural designers is the fact that due to its brittle tensile behaviour, timber tends to fail abruptly under the application of flexural loads. The presence of localized defects such as knots also tend to aggravate the problem as these localities are obviously not only weaker compared with the overall strength of the timber member considered, but also tend to be stress concentration regions. For engineered wood products (EWPs) such as glued laminated timber, the introduction of finger joints further compounds the predicament of the structural engineer as these joints are now crack initiation locations because these joints tend to open up when experiencing tensile forces due to flexural loads. However, it is possible to address these concerns by carrying out flexural strengthening of timber members using materials as varied as steel, fibre reinforced polymers (FRPs), biological fibres, and perhaps timber itself, albeit of a higher strength. This paper seeks to review the current strategies undertaken by international researchers to fortify and bolster the flexural strength of timber in order to make it an attractive construction material to architects, engineers and builders alike.

• Periodical: Applied Mechanics and Materials (Volume 735)
• Pages: 128-140
• DOI: https://doi.org/10.4028/www.scientific.net/AMM.735.128
• Online since: February 2015
• Authors: Shujaatullah Sheikh, Yusof Ahmad*
• Keywords: Engineered Wood Products, Fiber Reinforced Polymer (FRP), Flexural Strengthening, Glued Laminated Timber, Structural Timber

References

[1] Teng, J.G., Chen, J.F., and Lam, L. (2002), FRP-strengthened RC structures, John Wiley & Sons, Ltd., West Essex, England.

[2] FIB Bulletin 14 Technical Report (2001), Externally Bonded FRP Reinforcement for RC Structures, International Federation of Structural Concrete, Lausanne.

DOI: 10.35789/fib.bull.0014.ch01

[3] American Concrete Institute (ACI) (2002), Guide for the design and construction of externally bonded FRP systems for strengthening concrete structures, ACI-440, ACI-440 Committee, Detroit.

DOI: 10.14359/51700867

[4] Concrete Society (2012), Technical Report No. 55 – Design guidance for strengthening concrete structures using fibre composite materials, The Concrete Society, Surrey, United Kingdom.

[5] MS 544: 2001: Code of practice for structural use of timber, Department of Standards Malaysia, Shah Alam, Malaysia.

[6] Buchanan, A.H. (1990), Bending strength of lumber, ASCE Journal of Structural Engineering, Vol. 116, No. 5, 1990, pp.1213-1229.

DOI: 10.1061/(asce)0733-9445(1990)116:5(1213)

[7] André, A. and Kliger, R. (2009).

[8] Fiorelli, J. and Dias, A. A. (2003), Analysis of the strength and stiffness of timber beams reinforced with carbon fibre and glass fibre, Journal of Materials Research, Warrendale, PA, USA.

DOI: 10.1590/s1516-14392003000200014

[9] Yusof, A. (2013), Ductility of Timber Beams Strengthened Using Fiber Reinforced Polymer, Journal of Civil Engineering and Architure, USA, May 2013, Volume 7, No. 5 (Serial No. 66), pp.535-544.

DOI: 10.17265/1934-7359/2013.05.003

[10] Osmannezhad, S., Faezipour, M. and Ebrahimi, G. (2014), Effects of GFRP on bending strength of glulam made of poplar (Populus deltoids) and beech (Fagus orientalis), Construction and Building Materials 51 (2014), pp.34-39, Elsevier Ltd.

DOI: 10.1016/j.conbuildmat.2013.10.035

[11] Dagher, H., Gray, H., Davids, W., Silva-Henriquez, R. and Nader, J. (2010), Variable prestressing of FRP-reinforced glulam beams: methodology and behavior, World Conference on Timber Engineering (WCTE 2010), 20-24 June 2010, Trentino, Italy.

[12] Blaß, H. J., and Romani, M. (1998-2000), Reinforcement of glulam beams with FRP reinforcement. , University of Karlsruhe, Germany.

[13] Fiorelli, J. and Dias, A. A. (2011), Glulam beams reinforced with FRP externally-bonded: theoretical and experimental evaluation, Materials and Structures (2011) 44 pp.1431-1440.

DOI: 10.1617/s11527-011-9708-y

[14] National Research Council – Advisory Committee on Technical Recommendations for Construction (2007).

[15] Romani, M. and Blaß, H.J. (2001), Design model for FRP reinforced glulam beams, International Council for Research and Innovation in Building and Construction, CIB-W18, Venice, Italy.

[16] Khelifa, M. and Celzard, A. (2014), Numerical analysis of flexural strengthening of timber beams reinforced with CFRP strips, Composite Structures 111 (2014), pp.393-400, Elsevier Ltd.

DOI: 10.1016/j.compstruct.2014.01.011

[17] Guan, Z.W., Rodd, P.D. and Pope, D.J. (2005), Study of glulam beams pre-stressed with pultruded GRP, Computers & Structures 83 (2005) pp.2476-2487, Elsevier Ltd.

DOI: 10.1016/j.compstruc.2005.03.021

[18] Ogawa, H. (2000), Architectural application of carbon fibres, development of new carbon fibre reinforced glulam, Carbon, 38, 211-226.

[19] Lopez-Anido, R. and Xu, H. (2002), Structural characterization of hybrid fibre-reinforced polymer-glulam panels for bridge decks, Journal of Composites for Construction, 6(3), 194-203.

DOI: 10.1061/(asce)1090-0268(2002)6:3(194)

[20] Borri, A., Corradi, M. and Grazini, A. (2005), A method for flexural reinforcement of old wood beams with CFRP materials, Composites: Part B, 36, 143-153.

DOI: 10.1016/j.compositesb.2004.04.013

[21] Information on: http: /quakewrap. com/project_sheets/FRP%20Repair%20of%20Wooden%20Beams%20in%20High%20School%20Gymnasium. pdf (accessed on 1 July 2014).

[22] Gentile, C., Svecova, D. and Rizkalla, S. H. (2002), Timber beams strengthened with GFRP bars: development and applications, Journal of Composites for Construction, 6(1), 11-20.

DOI: 10.1061/(asce)1090-0268(2002)6:1(11)

[23] Kliger, R., Al-Emrani, M., Marie Johansson, M. and Crocetti, R. (2007), Strengthening Glulam Beams with Steel and Composite Plates, Proceedings of the Asia-Pacific Conference on FRP in Structures (APFIS 2007) Hong Kong, China, 291-296.

[24] Yusof, A. (2010), Bending behavior of timber beams strengthened using fiber reinforced polymer bars and plates, Ph.D. thesis, Faculty of Civil Engineering, Universiti Teknologi Malaysia, Johor, Malaysia.

DOI: 10.21833/ijaas.2017.03.001

[25] Buell, T. W. and Saadatmanesh, H. (2005), Strengthening Timber Bridge Beams Using Carbon Fiber, Journal of Structural Engineering. Vol 131, pp.1-199.

DOI: 10.1061/(asce)0733-9445(2005)131:1(173)

[26] Mokhtar, N.I. and Ahmad, Y. (2012), Reinforcing techniques using fiber-reinforced polymer: a review, APSEC-ICCER 2012, 2-4 October 2012, Surabaya, Indonesia.

[27] Kliger, R., André, A. and Haghani, R. (2013), Innovative Timber Composites: Improving wood with other materials, Composites 20+Polycon 09, 17th October 2013, Nicosia, Cyprus.

[28] André, A. (2006), Fibres for Strengthening of Timber Structures, PhD. Thesis, Division of Structural Engineering, Department of Civil and Environmental Engineering, Luleå, Sweden.

[29] Ranganathan, R. (2005), Structural reliability analysis and design, Jaico Publising House, Mumbai, India.