br The stone sail With regards to environmental and

The “stone sail” With regards to environmental and technological performance, it must be taken into consideration that the components being assembled dry promote the assembly and subsequent disassembly with full recovery of all elements. They, once disassembled, can be recycled or reused for other buildings (Zanelli, 2003; Lombardo, 2012). In order to define the feasibility of the new constructive procedure, a full-scale prototype was built. By analogy with the previous study, a portion of a spiral, a “sail” in blocks of Etna basalt was considered. This prototype, consisting of a panel with a thickness of 20cm, described by an inverted truncated conical surface, has a curvilinear with axis sloped from the vertical by 10°, height ranging from 0 to a maximum of 3.5m and length of the RGFP966 to 7.3m. The sail, without constraints in space throughout its height, at the base is fixed to a foundation of reinforced concrete with a size of 6.6×1, 63×0, 30m (Figures 1 and 2). In blocks, achieved by water jet cutting with a diamond disc, a cylindrical hole, with a diameter of 6cm has been made, using a corer, in order to make room for the reinforcements. The size of the blocks and the hole was studied in order to guarantee the staggered joints and alignment of the hole where the prestressed cable is placed through all the layers (Figures 3–5). The link system between the sail and the foundation is made up of several elements: one plate, galvanized steel (250mm×250mm×5mm), and a hollow cylindrical element, also made of galvanized steel, consisting of a tubular (F45×M30 l=350mm), threaded inside (Figures 6 and 7). The plate is completely embedded within the foundation and the tubular comes out from the top of the foundation (5cm), so as to allow the tightening between the foundation and steel threaded rods. The threaded rods (diameter 3cm, length 300cm), in galvanized steel, inside the hole, are placed from each other at a distance of 40cm, which corresponds to the size of the block. Where the sail has a height greater than 3m, the rods were linked by a sleeve (F45×M30 l=100mm) similar to the tubular used in the foundation, providing the absolute transmission of the stress as if it was a seamless single bar. The top closure system, at the last layer of blocks, is made up of a plate, also made of galvanized steel (150mm×150mm×5mm). The rod is linked to the block of head through the top plate and a steel nut (M30-quality 8.8). Each nut has been applied a specific value of tightening to give the required prestressing obtained from structural tests made according to the height of the sail at that point (Figure 8).
Assembly procedure In the foundation, once the steel reinforcement was prepared, the bottom plates were put in place with the threaded cylinder (located at a distance of 0.40m from each other according to a circular arc of radius 8.65m) and welded to the bottom reinforcement. The concrete casting to a height of 30cm was performed making sure to protect the top of the threaded cylinder. Once foundations ended, the first layer of blocks was placed by putting a layer of leveling to improve the adherence between the foundation and the same blocks. They were then clamped for each cylinder threaded rods, having been, in some cases shortened and in others, where the sail was over 3ft of height, stretched through the use of sleeves (Figure 9). Having prepared all the steel bars into their housing, we proceeded with the laying of each block. Up to a height of 1.8m, the building of the sail which took place by sliding the block along the steel rod was done fairly quickly and easily by a single worker, being the weight of the block (23kg) below that ergonomically permitted by the regulation for a worker. In the part of the sail that exceeded the height of 1.8m it was necessary to build a small scaffolding and have the support of a second worker who would help to slide the block along smoothly to the height of the steel rods up to the maximum of 3.5m.