Abstract :
[en] A general procedure for the evaluation of the mechanical properties of structural joints, named “component method”, is now available from intensive research works at the European level. This procedure allows the analytical prediction of the resistance, but also of the stiffness and the deformation capacity, of structural joints under external forces (axial or shear forces, bending moments …).
The component method is nowadays integrated as a reference procedure in two European de-sign codes, respectively for steel structures (EC3 [EN1993]) and steel-concrete composite structures (EC4 [EN1994]). However, its potential scope is much larger and present studies are aimed to apply to situations as joints in fire, joints under seismic loading, joints under exceptional loads (Robustness Project) ….
More recently, a research project [CTI-2004] has succeeded in applying the component method to the investigation of the elastic behaviour of mechanical joints in timber construction. That is the result of the collaboration of CTIB-TCHN (Belgian Institute for Wood Technology) and University of Liège.
The main principle of the component method is the following:
• identification of constitutive components subjected to tension, compression or shear in the joint;
• determination of the mechanical behaviour of these individual components;
• "assembling" components so as to derive the mechanical properties of the whole joint.
In the present paper, timber joints with dowel fasteners are considered. Two components may be identified:
• "dowel" component (dowel fastener in bending and shear);
• embedding component (timber member in embedding).
The "dowel" component is known from past researches, whereas little information is available for the embedding component. EC5 [EN1995] proposes formulation to predict the behaviour for joints composed of these two components; but it only depends on two factors: the dowel diameter and the timber density. The influence probably significant of the grain direction (material strongly anisotropy) and the thickness of the connected members are for instance neglected.
Experimental, numerical and analytical investigations have recently been performed by Uni-versity of Liège in collaboration with CTIB-TCHN so as to propose another formulation more precise for joints. Experimental results, performed by CTIB-TCHN, have been used as refer-ence for the development of numerical model and, then, analytical model. The application of the component method to the prediction of the elastic behaviour of timber joints consist of two steps:
• "local" investigation on components that is to develop analytical models for the pre-diction of the elastic behaviour of components;
• "global" investigation on joints that is to develop analytical models for the prediction of the elastic behaviour of joints.
The application of the component method to timber joints with dowel fasteners is a first step towards the use of this concept in future to others mechanical joints (screw, punched metal plate, nail, bolt …). In this case, others components may be derived to cover the field of ap-plication expected.
