China
Africa
Explore chapters and articles related to this topic
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.
Changi Airport station design and construction
Published in Jian Zhao, J. Nicholas Shirlaw, Rajan Krishnan, Tunnels and Underground Structures, 2017
This was achieved by first installing seven temporary plunge-in steel king posts. These king posts were cast into deep 2.8m × 1.2m barrette piles across the front of the car park. Each king post was fabricated from twin 356 × 406 × 393 kg/m sections with a typical vertical capacity of around 1000 tonnes. The ground beneath the existing structure was then excavated down to a level of approximately 3.5m below the existing pile caps to permit construction of the underpinning slab. Steel needle beams supported temporarily on each king post were cast in as an integral part of this slab. This resulted in a maximum beam span of 1 lm. The 2.0m deep fabricated sections weighed up to 35 tonnes and to lower the beams down into the excavation a full elevated temporary deck was constructed across the station box. Once lowered to the working level the beams were winched in beneath the existing structure, between the existing piles. After the beams had been bolted down additional steel reinforcement was fixed to the 2.8m thick underpinning slab. The composite slab was cast in one pour with 1100m3 of concrete and was debonded from the existing piles. After the concrete had achieved the required design strength the slab was undermined to allow it to deflect under self weight. The 39 no. hydraulic jacks between the slab and existing pile caps were then inflated to the predetermined loads to ensure full load transfer. The existing piles were cut using a wire saw at the soffit level of the underpinning slab and the excavation beneath the slab could then proceed to the next slab level.
Lessons from Structural Analysis of a Great Gothic Cathedral: Canterbury Cathedral as a Case Study
Published in International Journal of Architectural Heritage, 2021
Georgios Karanikoloudis, Paulo B. Lourenço, Leslie E. Alejo, Nuno Mendes
The nave roof is a classic high-pitched Gothic roof of about 54°, with a covering span of 11.1 m. The timber trusses, placed with a spacing of 3.5 m and fixed over timber wall plates, form a rigid timber framing system with hinged joints of timber connections and metallic-edged blades. They are configured of a queen post on the lower level and a king post over the level of the straining beam, along with a series of struts (Figure 7a). The whole system appears structurally independent of the nave vaults and extends over the extrados of the vaults by 0.8 m. The roof of the lateral aisles is single pitched of about 8°, with a covering span of 5.0 m. and a spacing of 2.7 m (centre axis) (Figure 7b). On the side of the buttresses, the tie beams rest on wall plates, along with an adjoining post and curved brace timber elements, fixed on a small cantilever, that counteract the bending and vertical forces. From the inner side, the tie beams and principal rafters are attached separately to the walls of the triforium. The external roof coatings in both the nave and lateral aisles are large size lead sheets, attached on a system of timber roof battens.
On-site full-scale tests of a timber queen-post truss
Published in International Journal of Architectural Heritage, 2018
Jorge M. Branco, Humberto Varum, Filipe T. Matos
The geometry of this particular truss is out of the ordinary: its configuration is typical of a king-post truss, but the queen-posts were added by connecting the joint strut/rafter to the tie-beam. This is not the traditional queen-post truss geometry, in which the king-post is substituted by a straining beam connecting horizontally (in the superior part) the two queen-posts, those located below the higher purlin, and the struts connecting the bottom part of the queen-posts to the lower purlins. Clearly, it is an example of a timber truss with an incorrect configuration for the span of the roof. The correct queen-post truss geometry should have been used or two extra posts (princess-posts) should have been placed below the lower purlin. Point loads out of the joints, causing bending moments in the rafters, are the most common error detected in the preliminary survey performed in previous steps of the research program (Branco et al. 2006).
The assessment of Italian trusses: survey methodology and typical pathologies
Published in International Journal of Architectural Heritage, 2018
Nicola Macchioni, Massimo Mannucci
Independent from the complexity of the schemes, the efficiency of the structural joints connecting each member is crucial for the functioning of the frame. The most strained are for sure the tie-beam to rafter joints and the rafter to king post joints, but also the strut to king post joints, when present, are important. The analysis of the efficiency of an existing, historic truss starts from the visual survey of the efficiency of its structural joints.