Lapped scarf joint with inclined faces and wooden dowels: Experimental and numerical analysis

• Full scale traditional carpentry joint tested using experiments and numerical modeling.
• Width of the lap element should be kept as half of the beam width.
• Jointed beam provides between 65% and 75% of the original beams’ strength.

Experimental and numerical analysis were performed to investigate the mechanical behavior of a lapped scarf joint with inclined contact faces and wooden dowels which is a commonly used connection for repairing damaged beams in historical structures. This study aimed to define and suggest most effective parameters that influence this particular joint’s performance. Experimental testing was done on the full scale specimens. Four- and two-dowel-joints with half-beam-width laps and with 3/8-beam-width laps were tested. Experimental data analysis concluded that the width of the lap element should be kept as half of the beam width, therefore this type of joint was further analyzed using numerical approach. Finite element models were constructed for joints with four, two, and three wooden dowels. These models and theoretical criterion according to EC5 were used to select a number of dowels used for connection, joint’s length and location. It was concluded that a lapped scarf joint with 3 wooden dowels that is 1.38 m long and located at 1/5 L from support is the most efficient joint (in terms of strength, stiffness, and manufacturing) for the beam-end reparation; however, location of joint must consider both preservation of the most of the original material and the extent of damage. Numerical model can be used for designing joints with different parameters in beams with different dimensions. It was also calculated that a jointed beam provides between 65% and 75% of the original beams’ strength while the linear stiffness is not influenced significantly.