A "teethed beam" is a composite beam consisting of multiple beams which are connected with sawtoothlike joints. These composite beams can already be found in illustrations of ancient roman bridges. Until the late 19th century these composite beams were used to realize large span widths with heavy loads – e.g. ceiling constructions in town halls and churches but also in bridges and roof constructions. The teethed joint was supplanted due to the development of novel connection means like hard wood dowels, steel dowels and specifically designed dowels. Since the development of the glulam timber in the 20th century the teethed beams only played a role in maintenance. From a cultural heritage preservation’s point of view these beams have to be preserved and maintained carefully. The maintenance of a 270 year old church tower’s roof construction is a good example for the preservation. In this case five teethed beams served as suspender beams for the ceiling construction which supported the roof construction. The teethed beams partially showed biotical damages on the supports so that they had to be replaced. Unfortunately, there are no design rules for the teethed joint in the existing timber construction literature since the 1970s. Therefore, studies on the load bearing capacity and the load-deferral behavior of composite beams with teethed joints were carried out at the Univeristy of sustainable development Eberswalde. The results showed that the shifting modulus of a teethed joint is equivalent to the shifting modulus of a specifically designed dowel (type C1, Ø140 mm according to EN 912).
