Cristóvão L. Santos

Results of a double-shear single-dowel wood connection tested under monotonic quasi-static compression loading are presented and discussed in this paper. The wood used in this study was a pine wood, namely the Pinus pinaster species, which is one of the most important Portuguese species. Each connection (specimen) consists of three wood members: a centre member, loaded in compression along the parallel-tograin direction and two simply supported side members, loaded along the perpendicular-to-grain direction (Tconnection). The load transfer between wood members was assured by means of a steel dowel, which is representative of the most common joining technique applied for structural details in wooden structures. The complete load-slip behaviour of the joint is obtained until failure. In particular, the values of the stiffness, the ultimate loads and the ductility were evaluated. Additionally, this investigation proposed non-linear 3D finite element models to simulate the T-joint behaviour. The interaction between the dowel and the wood members was simulated using contact finite elements. A plasticity model, based on Hill’s criterion, was used to simulate the joint ductility and cohesive damage modelling was applied to simulate the brittle failure modes (splitting) observed in the side members of the joint. The simulation procedure allowed a satisfactory description of the non-linear behaviour of the T-joint including the collapse prediction.

Wood and wood products are amongst the most important construction materials. Wood is generally used in frames, buildings, truss roof structures in buildings, bridges, towers, railroad infrastructures, and many more applications. Damage and failure behaviour of wood members in tensile, compressive, or shear loading are extremely important to account for in wooden structures subjected to high working stresses. Wood exhibits its greatest strength in tension in the grain direction. A few applications load a wood member in pure tension, such as trusses in the most varied applications. For a safe design, predictive methods and models for the simulation of the structural behaviour of these elements are required. One of the possible approaches is the finite element method. In this work, the tensile strength of adhesively bonded repairs with carbon-fibre reinforced plastic patches on wood members in pure tension is addressed experimentally and numerically. A parametric analysis was carried out on the overlap length (L_O) between the composite reinforcement and the undamaged region of the beam. The numerical analysis used the finite element method and cohesive zone models to simulate damage initiation and propagation in different materials such as the adhesive or wood in different propagation planes. The comparative analysis of the test results and the simulations showed a good correlation between both and provided design principles for these structures. An optimization technique to reduce stress concentrations and eventually increase the repair's strength was also tested numerically, consisting of adhesive filleting at the patch edges. Results showed that this technique can be used to increase the strength of the repairs.

Abstract:  The purpose of this paper is to provide a comparison between embedding tests covered by the EN383 and ASTM D5764 standards, highlighting some difficulties regarding the application of the referred standards. These embedding tests are essential to evaluate the embedding strength of wood, which is required for the assessment of joints strength. The proposed comparison is based either on experimental data and numerical simulations through the finite element (FE) method. Tests were performed on maritime pine wood (Pinus pinaster Ait. species) according to the longitudinal and radial directions, allowing the comparison of the embedding strength and elastic foundation modulus. Three dimensional FE models of the tests were built using contact elements technology and assuming the steel dowel and wood as linear elastic isotropic and orthotropic materials, respectively. The contact modelling is a challenging topic for which this paper also proposes some guidance. The test configuration proposed in the EN383 standard for assessment of the embedment strength in compression is more susceptible to the dowel bending than the half‐hole test configuration proposed in the ASTM D5764 standard. The numerical simulation of the EN383 embedding test raises some additional difficulties regarding the dowel boundary conditions.