ASSESSMENT OF ALTERNATIVE REPAIR TECHNIQUES OF RAFTER-TIE BEAM CONNECTIONS

Timber trusses have been widely use in the medieval buildings, but also in the modern ones. In the timber trusses structure the most important connection is the so-called rafter-tie beam. The destruction of the connections and as a consequence the diffraction of the timber trusses normally occurs because of the overload or natural degradation by biological agents of the truss structure. In those cases there is a need of connections repair and the identification of simple and efficient repair techniques is very important for the normal function of the truss for a long period of time. The evaluation of two repair techniques of rafter-tie beam is in the focus of this study.Tests are conducted in connections composed of elements with 15x15 cm of section, from several timber species namely, poplar (Populus sp.), white fir (Abies alba Mill.), spruce (Picea abies Carst.) and chestnut (Castanea sativa Mill.). The connections tested originate partly from beams used in old/medieval buildings and partly from new beams. After the mechanical tests, the rafter-tie connections were repaired and tested again, which allowed us to compare the functional performance of the original and the repaired connections. We evaluated two repair techniques, one consisting in adhesive bonding of heel above parts separated during the mechanical tests, using a special wood adhesive and the second technique consisting in using metal tie elements, which don’t affect the dynamics of the connection. Tests results are showing that all the repaired rafter-tie beam connections, despite the repair techniques used are functional under the same and in some tests under higher forces that the ones measured during the destructive mechanical tests.