Search

Joints play a major role in the structural behavior of old timber frames (Descamps et al., 2014) [1] . Current standards mainly focus on modern dowel-type joints and usually provide little guidance (with the exception of German and Swiss NAs) to designers regarding traditional joints. With few exceptions, see e.g. [2–4] , most of the research undertaken today is focused on the reinforcement of dowel-type connections. When considering old carpentry joints, it is neither realistic nor useful to try to describe the behavior of each and every type of joint. The discussion here is not an extra attempt to classify or compare joint configurations (Gerner, 2012) [5,6] , (Seike, 1977) [7] . Despite the existence of some classification rules which define different types of carpentry joints, their applicability becomes difficult. This is due to the differences in the way joints are fashioned depending, on the geographical location and their age. In view of this, it is mandatory to check the relevance of the calculations as a first step. A limited number of carpentry joints, along with some calculation rules and possible strengthening techniques are presented here.

In European seismic areas timber structures are found as building frames, in combination with masonry infills, in bridges, but most frequently in roof structures and floor slabs of traditional buildings. Seismic strengthening of existing structures should provide a well-defined and simple path to seismic forces, maintain timber members elastic, and develop as much as possible the post-elastic behaviour of joints. Provisions must be adopted to avoid sudden loss of capacity and brittle failure, and to foster ductility. Different criteria for seismic strengthening of floor slabs and of carpentry joints are presented.

Carpentry joints have been dimensioned in the past with global statics considerations. New design requirements impose considering the response to exceptional as well as to ordinary loading and require a more detailed knowledge of the mechanical behavior. A typical double-step joint, common in the rafter to tie-beam node of large-span trusses, has been studied numerically for monotonically increasing axial compression in the rafter and for cyclic rafter rotation up to ultimate conditions. The stress distribution at the contact surfaces as well as the rotational stiffness and ultimate moment for different levels of axial force have been evaluated. Results, compared with other joint types, show a good degree of interlocking and confirm a better performance of this joint in sliding shear.