Evaluation of a design approach to the on-site structural repair of decayed old timber end beams

In this paper the reliability in the load predicting ability of a design approach currently used in Italy for the repair of decayed end-beams of old elements was experimentally evaluated. The evaluation was carried out by using two different epoxy resins and two different materials for the connecting rods (namely steel and CFRP), used both on new graded beams and on 70 years old elements. Results evidenced that specimens failed invariably at the prosthesis side (and not at the solid wood side), and that for larger sections load values were higher than those obtained on the basis of calculations. However, the expected mechanism of collapse (i.e., pull-out of glued-in rods) was never observed in tests, except as a consequence of other failure mechanisms. In contrast, specimens evidenced the splitting of wood close to rods, which was unexpected according to the considered design approach. Several criteria were compared in order to take account of the experimental evidences, and among them, one was the best performing. Although this work evaluated an approach also based on a national document, the results achieved and the fact that similar procedures are also considered in other national codes give to the outcomes a general validity, which can be effectively applied in similar cases.

► A design criterion to repair timber end-beams has been experimentally evaluated.
► Collapse values higher for larger sections, although not predicted by design method.
► A failure mechanism unexpected on the basis of the design approach was found.
► Some criteria to consider wood splitting were evaluated and one of them proposed.
► Material types do not influence performances if the junction is safely designed.