Edinburgh Napier University

  The orthotropic nature of timber creates issues with regards to dimensional stability and strength in most shell/surface structures and i particular in liquid-retaining wooden containers. Oak barrel, traditionally used for the transportation and storage of food, and more recently liquid, are susceptible to the orthotropic behavior of timber with no consideration of this phenomenon on their time-honoured design. The multi-componenet end plates expand in confined areas due to changes in moisture content. The orthotropic nature of timber results in non-uniform expansion with respect to grain orientation, resulting in warping of the barrel ends. Loss of liquid content occurs as a result of the movement in joints due to this warping, which can be reduced if additional stiffness can be incorporated into the structure to reduce expansion.
Various methods of cross-lamination techniques have been investigated both numerically and experimentally, to establish the efficiency of stress transfer from the main timbers to the supoprts. Traditional glued-lamination method may not be an option on industrial scale barrel manufacture as a result of possible product contamination; therefore alternative glue-free lamination methods have been developed. CAD designed dowel arrangements and dovetail jointing solutions have been numerically assessed using finite elements analysis (FEA) to produce optimal cross-laminated timber and reduce the effects of the orthotropic nature of the end plates with the aim of decreasing non-uniform expansion, and therefore limiting joint movement. Optimised cross-laminated timber, using alternative jointing methods, has been compared to similar glued cross-laminated timber to assess the efficiency of the jointing with respect to stress transfer and dimensional stability.