Behaviour of Timber Lattice Beams With Semi-Rigid Joints: Analytical and Experimental Study

The behaviour of standardized lattice timberbeams in bending with semi-rigid joints is studied.Various measurement techniques are used in theexperiments to measure the displacements androtations of the glued and/or nailed joints. Theexperimental results, obtained on beams withdifferent types of joints combining glue and nails, arepresented. The description of the nails, theadhesives and the types of wood is detailed. Theexperimental results in terms of load-deflectioncurves, crack features, due to nails and adhesives,are presented. The semi-rigidity of the joint betweenvertical bracing and diagonal struts is analysed. Thecomparison of various measurements techniquesshowed the validity of the experimental results.These results showed the influence of the axial andthe rotational semi-rigidity of the joints on the globalbehaviour of the beams. The experimental resultsare compared with the analytical results given by theEuler-Bernoulli beam theory, including or not thelinear semi-rigid stiffness of the joints in tension orcompression. The study shows the satisfactorybehavior of the lattice beams and gives informationon the opportunity to choose one of the gluingtechniques to fulfill the mechanical requirements ofthe beams. The study also shows the necessity of amore complete modeling taking into account the effect of the rotation in the joint area and the influence of the nonlinearity on the global behaviour of the beam.