Adhesive Connections in Timber: A Comparison between Rough and Smooth Wood Bonding Surfaces

The use OF adhesive anchors for wooden constructions is an efficient technology to connect and design timber members in new timber structures and to rehabilitate the damaged structural members of historical buildings. Due to the lack of standard regulation in this specific area of structural design, designers’ choices are still supported by test analysis that enables knowledge, and the prediction, of the structural behaviour of glued in rod joints. The paper outlines an experimental research activity aimed at identifying the tensile resistance capacity of several new adhesive joint prototypes made of epoxy resin, steel bar and timber, Oak and Douglas Fir species. The development of new adhesive connectors has been carried out by using epoxy to glue stainless steel bars into pre-drilled holes, characterised by smooth and rough internal surfaces, in timber samples. The realization of a threaded contact surface using a specific drill bit has led to an improved bond between wood and epoxy. The applied changes have also reduced the cost of the joints’ production. The paper presents the results of this parametric analysis and a Finite Element analysis that enables identification and study of the internal stress distribution in the proposed adhesive anchors.





References:
[1] D.O. Chans, J.E.Cimadevila, and E.M. Gutiérrez, “Glued joints in hardwood timber,” International Journal of Adhesion & Adhesives, vol. 28, 2008,pp.457-463.
[2] D. Otero, M. Estevez, E. Martin, J. A Vazquez, “Failure modes in double-sided pull-out test of threaded steel rods glued in hardwood,” 2010 WCTE World Conference Timber Engineering.
[3] D.Yeboah, S. Taylor, D. McPolin, R. Gilfillan, S. Gilbert, “Pull-out behaviour of axially loaded basalt fibre reinforced polymer (BFRP) rods bonded parallel to the grain of glulam elements,” The Sructural Engineer, 2012,pp.42-51.
[4] C.Bengtsson, M.Kemmsies, C.-J. Johansson, “Production control methods for glued-in rods for timber structures,”in Proceedings of the 6th World Conference on Timber Engineering, Whistler Resort, Canada, vol. 1, paper 7-4-1, July-August 2000.
[5] A.Gubana, “Collegamenti unioni incollate,” Presentazione del documento CNR-DT 206/2007. Facoltà di Ingegneria- Università di Udine, 2008.
[6] K. Harvey, M.P. Ansell, “Improved timber connections using bonded-in GRRP rods,”in Proceeding of the 6th World Conference on Timber Engineering, Whistler Resort, Canada, paper P04, August 2000.
[7] TradaTecnology,“Bonded-in Rod Connections For Timber Structures,” (GIRODS), 2000 (online). Available at: < http://research.ttlchiltern.co.uk/girod/girod.htm >
[8] M. Del Senno, M. Piazza, and R.Tomasi, “Axial glued-in steel timber joints - experimental and numerical analysis,” HolzalsRoh- und Werkstoff, vol62, 2004, pp.137-146.
[9] M.Stepinac, “Joints in beech-LVL timber frames,” report of a Short Term Scientific Mission, University of Zagreb, 2013, Croazia: COST Action FP1004.
[10] G. Tlustochowicz, E. Serrano, R. Steiger, “State-of-the-art review on timber connections with glued in steel rods,” Materials and Structures, vol 44, 2011, pp.997-1020.
[11] Product information, 2K Polymer Systems Limited, 2014.
[12] J. E. Cimadevila, D.O. Chans, E. M. Gutierrez, “Adhesive multi-bulbs: A novel anchoring system using threaded steel rods glued into wood, ”Construction and Building Materials, vol 48, 2013, pp.131-136.
[13] Handbook 1- Timber structures. TEMTIS, 2008, ch. 3.
[14] M. Stepinac, F. Hunger, R. Tomasi, E. Serrano, V. Rajcic, J.-W. Van de Kuilen, ”Comparison of design rules for glued-in rods and design rule proposal for implementation in European standards,” Internal Council for research and innovation in building and construction -working commission W18- timber structures, August 2013.
[15] Bonding with Epoxy in Woood Construction, Gurit, 2002 (online). Available at: < http://www.gurit.com/files/documents/bonding-guidepdf.pdf >
[16] D.O. Chans, J.E. Cimadevila, and E.M. Gutiérrez, “Withdrawal strength of threaded steel rods glued with epoxy in wood,” International Journal of Adhesion & Adhesives, vol 44, 2013, pp.131-136.