Reinforcement of glulam elements subjected to large local compression perpendicular to the grain using self-tapping screws

摘要

Timber is relatively weak if subjected to loading that causes compression perpendicular to the grain. Normally, such a kind of loading does not lead to a structural collapse, but the deformations which take place can be of such a magnitude that the serviceability of the structure might be affected. This is the case, for example, of a heavily loaded beam lying on a column with a relatively small cross section. In some cases, however, the deformations caused by compression perpendicular to the grain can also lead to a reduced loading bearing capacity of the structure. This can occur, for example, in stress-laminated bridge decks. In such a case, in fact, a local deformation due to compression perpendicular to the grain, at the anchorage of the steel prestressing rod, causes a loose of prestressing force in the rod which in turns may lead to a reduced loading bearing capacity of the deck. The technique of inserting full-treaded self-tapping screw was adopted on some ten specimens to increase the loading bearing capacity of anchorage system for stress laminated bridges. The diameter, the length and the spacing of the screws was chosen in order to optimise the loading bearing capacity of the anchorage and avoid buckling of the screws.