The Repair of Timber Beams with Controlled-Debonding Steel Plates
In this paper a non-invasive technique for the repair of ancient wooden floors is presented. Steel plates are glued on one side only by epoxy-adhesive into longitudinal grooves in order to allow the free swelling and shrinkage of the wood in the direction transversal to the plate glueing surface, thus reducing the risk of plates’ delamination. A set of high strength steel nails guarantees the transmission of the load from the steel plates to the wooden beam in case of loss of adhesion due to fire or delamination. This technique was used to repair a precious beam in a wooden floor of the 15th century in Palazzo Calini (Brescia, Italy). The presented technique requires particular attention because it might be affected by the delamination of the glued reinforcement due to the stress concentration, which occurs at the end of the repairing element or at the cracks of the repaired beam.The main results of experimental and numerical studies focusing on the delamination phenomenon are also presented and discussed. They have shown that the risk of plate debonding can be markedly reduced by the capability of the sapwood to develop plastic strain. The wooden floor has been monitored for more than eleven years, confirming the effectiveness of the adopted technique. The monitoring has also shownthe importance of limiting the wooden moisture content variation to reduce the floor’s creep deflection.
Maurizio Piazza and Mariapaola Riggio
G. Metelli et al., "The Repair of Timber Beams with Controlled-Debonding Steel Plates", Advanced Materials Research, Vol. 778, pp. 588-595, 2013