Edinburgh Napier University

  Flitch beams are a form of sandwich construction using steel and timber elements. They are used in the construction of domestic dwellings when relatively high loads and long spans predominate but available depth of section is restricted in some way. Traditional flitch beams use a bolted connection to hold the elements together, which is a time consuming method of fabrication requiring the pre-drilling of holes in the steel and timber elements. It also presents problems in design detailing. Bolt slippage and fabrication tolerances result in disproportionate stress transfer due to uneven strain affecting the stiffness and strength properties of the beam. This paper details the findings from a series of laboratory tests and parametric studies on flitch beams constructed from either Kerto S Laminated Veneer Lumber (LVL) or C24 grade timber using a shot-fired dowel connection. The tests showed that during the elastic range proportional stress transfer took place. However, at higher load levels there is uneven stress transfer due to localised buckling of the steel in the top chord and a weakening of the timber elements of the beam due to splitting at the nailing points.