P.D. Rodd

Hollow steel dowels — a new application in semi-rigid timber connections

Dowel type fasteners used in timber joints are traditionally of solid cross section. The rigidity of those with a larger diameter increases the chances of brittle failure in the timber components. Hollow fasteners of variable wall thickness, whilst maintaining the required timber performance, offer variable fastener rigidity and the likelihood of enhanced joint ductility. This paper describes a finite element based model which was validated against the results of a series of tests on single hollow steel dowel timber joints and then used to conduct a parametric study of the effect of fastener wall thickness on joint performance.

Finite element modelling of OSB webbed timber I-beams with interactions between openings

Experiments were conducted on beams with openings spaced at different intervals along the web. It was observed that the OSB fractured from tension zones around an opening, with cracks developing diagonally towards the beam flanges. A beam would collapse when the cracks reached the flanges. Interactions between openings further reduced the load carrying capability of a beam and changed its failure pattern. Using ABAQUS, Finite element models were developed to simulate beam behaviour. Material nonlinearity, fracturing of OSB, crack propagation and beam failure were dealt with by a user subroutine. Good correlation was obtained between test and analytical results. Critical distances between openings were also investigated.

A constitutive model for OSB and its application in finite element analysis

Experiments were conducted to determine some of the material properties of OSB. Tests covered three in-plane board directions and the through thickness direction. Results showed that OSB is an orthotropic material with better material properties in the direction of strand orientation. OSB in tension behaves almost linearly up to failure, whilst in compression it exhibits plasticity. This plasticity needs to be taken into account in nonlinear finite element analysis in order to simulate the structural behaviour of OSB appropriately. An elasto-plastic constitutive model for OSB in compression was established, based on the statistics of test results. The model was used in the FE simulation of a load test on a compression specimen and a nonlinear buckling analysis of an OSB webbed timber I-beam. The close prediction of behaviour of both specimens was considered to act as validation of the proposed constitutive model.ZusammenfassungVersuche zur Bestimmung einiger Materialeigenschaften von OSB wurden durchgeführt. Die Versuche umfassten Prüfungen in drei Richtungen der Plattenebene, sowie eine Prüfung quer zur Plattenebene. Die Ergebnisse zeigten, dass OSB ein orthotropes Material mit besseren Materialeigenschaften in Richtung der Spanorientierung ist, während es sich bei Zugbeanspruchung hingegen plastisch verformt. Dieses plastische Verhalten muss bei nicht-linearen Berechnungen berücksichtigt werden, um das Festigkeitsverhalten von OSB richtig zu simulieren. Auf Grundlage der statistischen Versuchsergebnisse wurde ein elasto-plastisches Modell für OSB unter Druckbeanspruchung entwickelt. Das Modell wurde für die FE-Simulation eines Druckversuches und eine nicht-lineare Knickberechnung eines I-Balkens mit OSB-Steg verwendet. Die gute Übereinstimmung der Ergebnisse in beiden Fällen bestätigte die Eignung des Modells.