Experimental Study on the Effect of Moisture on Bolt Embedment and Connection Loaded Parallel to Grain for Timber Structures
Abstract
Connections are critical parts of timber structures, transmitting static and dynamic forces between structural elements. The ultimate behaviour of a building depends strongly on the structural configuration and the capacity of its connections. The complete collapse of a building or other less extensive accidents that may occur usually start as a local failure inside or in the vicinity of a joint. The main aim of this study has been to investigate if the short-term capacity of steel-wood dowel joints loaded parallel to the grain is affected by variations in moisture content associated with post fabrication drying or wetting of the timber. Extensive experiments were conducted. The experimental results showed that the stiffness and load-bearing capacity of the joints is reduced by post-fabrication wetting and is increased by post-fabrication drying. It was clear from those test results that changes in mechanical properties were greater than could be explained by effects moisture content changes have on material properties, implying that simple adjustments of properties in that way for purposes of structural design are unreliable Currently in the design of timber connection in code of practise is the effect of variation of moisture is not considered. The results revealed that there is a great effect on timber performance which is due to an increase of moisture content.
Keywords: Beam, creep, wood, heat transfer, hydrothermal strain, moisture strain.
References
Asiz A. and Smith I. (2009). Study on differential shrinkage in hybrid multi storey timber concrete building. In publication, University of New Brunswick, Fredericton NB, Canada.
Dinwoodie J.M. (2000). Timber: Its nature and behaviour. Second edition, E. & F.N. Spoon, London.
Eriksson J. (2005). Moisture transport and moisture induced distortions in timber €“ an experimental and numerical study.
PhD Thesis, Chalmers University of Technology, Gothenburg, Sweden.
Forest Products Laboratory (2011). Wood as an engineering material. Handbook, Washington, DC: US Department of
Agriculture, 466p.
Canadian Standards association (CSA) (2009). Engineering design in wood, Standard 086-09, CSA, Toronto, ON.
Canadian Standards Association (1994). Engineering design in wood. Standard 086-09, CSA, Toronto, Canada.
Johansen K.W. (1949). Theory of timber connections, Publications for International Association for Bridge and Structural Engineering, Zurich, Switzerland, 9: 249-262.
Jönsson J. (2004). Internal stresses in the cross-grain direction in glulam induced by climate variations. Holzforschung,
: 154-159.
Kharouf N., McClure G. and Smith I. (2005). Postelastic behavior of single- and double-bolt timber connections. Journal of Structural Engineering, American Society of Civil Engineers, 131(1): 188-196.
Mirianon F., Fortino S., and Toratti T. (2008). A method to model wood by using ABAQUS finite element software: Part 1 - constitutive model and computational details. Publications 687, Technical Research Centre, Espoo, Finland.
Ormarsson S. (1999). Numerical analysis of moisture-related distortions in sawn timber. PhD Thesis, Chalmers University of Technology, Gothenburg, Sweden.
Quenneville J.H.P. and Mohammed M. (2000). On the failure modes and strength of steel-wood-steel bolted timber connections loaded parallel-to- grain. Canadian Journal of Civil Engineering, 27: 761-773.
Quenneville J.H.P. and Mohammed M. (2001). Design method for bolted connections loaded perpendicular-to- grain. Canadian Journal of Civil Engineering, 28: 949-959.
Ranta-Maunus A. (2003). Effects of climate and climate variations on strength. In: Timber engineering. England, 153-167.
Rammer D.R. and Winistorfer S.G. (2001). Effect of moisture content on dowel-bearing strength. Wood and Fiber Science, 33(1): 136-139. Gothenburg, Sweden.
Smith I., Snow M., Asiz A. and Vasic S. (2006). Failure Mechanisms in Wood based materials: A review of discrete,
continuum, and hybrid finite element representation. Selected article from 7th WCCM, Los Angeles, USA, 61: 352- 359.
Smith I., Landis E. and Gong M. (2002). Fracture and fatigue in wood. John Wiley and Sons, Chichester, UK.
Sjodin J. (2007). Strength and moisture aspect of steel €“timber dowel joint in glulam structures €“ An experimental and Numerical study. Doctoral Thesis, Växjö University, Sweden.
Whale L.R.J. (1988). Deformation characteristics of nailed or bolted joints subjected to irregular short- or mediumterm lateral loading. PhD Thesis, London South Bank University, London, UK.
