Timber trusses in Italy: the progressive prevailing of open-joint over closed-joint trusses

The time and the place in which trusses were invented is uncertain; however, it is certain that they were already in use during Roman Empire. The oldest extant material evidences date back to the 6th century AD and witness the simultaneous presence in Italy of two constructive types that coexisted for centuries. The two types of truss are distinguished from each other based on the different relationship between posts and tie-beams: in closed-joint trusses, posts are connected to tie-beams with carpentry joints (e.g. tenon-mortise); in open-joint trusses, the posts are physically detached from the tie-beam but possibly linked to it with a metallic strap.