Keywords: timber structures, joint, beam, pin, key, peg.

Repair of historical timber structures leads to connecting existing and new beams. The requirements for beam authenticity leads to older ways of connecting beams. In most cases, e.g. floor structures, the second limit state: serviceability is of decisive importance. The new connection softens the beam and increases displacement. The most common joint is a scarf joint with two or more bolts or pegs. It is not clear how many bolts affect the beam stiffness. In Germany, the scarf joint with four bolts is recommended, but from the structural perspective it is not validated. The behaviour of joints with either two or four bolts seems the same.

In the process of repairing old timber structures, the widely used joint is with wooden pegs. It is possible to combine one pin with two keys or two keys with a pin. At the present time, the relevant information about the joint behaviour is missing and practical engineers require it. Simplifications, demanded by a theoretical solution, are derived from experimental results. The force method (based on the elastic strain energy) is used for the theoretical solution of a statically indeterminate structure.

The results of theoretical computing are very encouraging. The final stiffness changes of repaired beams compared with the original ones are in very good agreement with the experimental results.

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