Static behaviour of the selected carpentry joints in the flexural elements

Abstract

The paper presents the static behaviour of the selected carpentry joints in the bending wooden elements. Experimental research on beams with the carpentry joints created according to the geometry of the historical joints was conducted. It was confirmed that some of the longitudinal joints applied in the historical structures, with the proper strengthening elements, could transfer some bending moments, which is important in the flexural elements. The load-carrying capacity of the joined beams was determined and compared to the load-carrying capacity of the reference continuous beams, which was from 30 % to 40 %, depending on the joint geometry. Moreover, the stiffness level of the joined beams was determined and compared to the stiffness of the reference continuous beams, which was from 35 % to over 60 %, also depending on the joint geometry. The force-deflection plots for the tested beams were presented. The failure patterns for the joints were described and based on them the areas of stress concentrations in the joints were identified. The joints worked asymmetrically and their failure occurred as a result of gradual loosening and then cracking – interruption of the continuity of the wood fibres. The role of the applied fasteners, which to some extent protect against loosening of the joints, and partially transfer the applied load, was confirmed. The obtained results were compared to the results from the literature regarding similar connections. Research results can be helpful in designing and performing repair and conservation work in historic wooden structures with carpentry joints, in the event of, for example, the need to recreate a historical joint or replenish part of the substance in an existing joint.