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Large span timber roofs in Italy between the 16th and 19th centuries
Published in João Mascarenhas-Mateus, Ana Paula Pires, Manuel Marques Caiado, Ivo Veiga, History of Construction Cultures, 2021
Simple (or classic) Italian trusses are historically characterized by the tie beam, the king post in tension and two struts in compression, added to reduce bending in the rafters (Figure 1). In the classic scheme the king post is detached from tie beam and the two are connected by U-shaped metal straps. In such a way the vertical load is not transferred to the tie beam, which only has to resist the outward thrust from the principal rafters in addition to the load of its own weight. This scheme works especially if the trusses are assembled on the ground, in such a way that the tie beam is not subjected to any bending, and then raised up to the roof. Above 10–12 meters the trusses are usually too heavy to be lifted in one piece; therefore, they are often equipped with a collar beam and queen posts and lifted element by element, taking the name of Palladian trusses (capriate palladiane). In Palladio’s Four Books there is evidence of drawings with such trusses, even if it is not clear for us how they were built; the popularity of the term palladiane is probably derived from the reputation of the architect. Unfortunately, the terminology is still confused today, as many authors refer to Palladian trusses as classic types.
Pitched roof structure
Published in Derek Worthing, Nigel Dann, Roger Heath, of Houses, 2021
Derek Worthing, Nigel Dann, Roger Heath
Some older roof structures have timber trusses to support the purlins. These are substantial triangulated structures formed with large section timbers. They are jointed, bolted and/or strapped together. They are capable of spanning from external wall to external wall and were quite common in the past in large buildings, where big rooms resulted in few loadbearing walls. The function of the truss is to support the purlins in the absence of such loadbearing walls. On very wide buildings, such as old warehouses, churches and chapels, trusses may support three or four purlins on each slope. They are very rare in modern construction although a lightweight version was popular in the 1950s, designed by the Timber Research and Development Association (TRADA), as a response to the post-war shortage of materials. Trusses can be found in a variety of designs. The left-hand example in Figure 8.18 is a king post truss. The king post is the vertical element in the centre of the truss.
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Published in Les Goring, Residential Surveying Matters and Building Terminology, 2023
King-post roof truss: See Figure 55: A historic timber truss (still seen in large, well-built roofs) consisting of a horizontal tie beam, a central kingpost that rose up from the beam to support the ridge board, and two side struts that emanated from the lower sides of the kingpost – forming a Y shape – to support the principal rafters and purlins on each side.
Historical and Constructive Study of Plank Timber Vaults in Madrid, Spain
Published in International Journal of Architectural Heritage, 2021
Marina Arce-Blanco, Francisco Arriaga-Martitegui, Ignacio Bobadilla Maldonado, Luis Gil
- The most common main roof structure corresponds to a simple truss consisting of rafters and tie beams (33%) for short span, and a braced king post truss, consisting of rafters, struts, tie beams and kingpost (33%) in the cases of large span. Pair and knuckle armour were found in 20% of the visited vaults.