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Since the civil construction adopted the reinforced concrete technology, the column manufacture has been being a hand-crafted process in which vertical boxes are set up containing long proper steel rods in their interior; these boxes are filled with cement mixed with water, sand and crushed stones, which the so-called concrete is consisted of.
The FIGS. 1,2 and 3 show this process and its stages.
In the FIG. 1, we can see the initial stage of the process, in which the steel rods (2) are placed vertically on any support (12) and they are kept in the position by their own stiffness or they are fastened with wires (3).
In the FIG. 2, the rods are kept in position by the hangers (4), which may occur at any number, usually according to the structural project, and they are also made of the same steel as the rods are, and they are stuck to the rods by either welding or wire fastening.
The FIG. 3 is a general frontal view of a pillar (5) which is being built and at this stage it is wrapped in a wooden mold (6), whose frontal part has been omitted in order to reveal the inside of the pillar, which will be removed when the concrete that will be placed in its interior is cured.
The hangers (4) usually have a gauge which is smaller than that of the main ironwork and they are obtained by their own cutting and folding at the proper dimensions and shapes, according to FIG. 4, where we can see the hanger from an upper view, here in a rectangular shape; it may take other polygonal shapes, though, such as that of a square, a triangle, a hexagon, etc.
The raw material offered by the market to be used as rods usually has the specific section (7), showed in the FIG. 5, called rounded core rod, and the specific surface (8), showed in the FIG. 6, known as corrugated surface. These specific shape and surface are intended to increase the contact area and the adhesion of the rod steel (2) and hangers (4) with the concrete, raising the whole resistance.
However, when the rods (2) are folded to make the hangers (4), due to the specific section of the material, the polygons (9) which are formed do not keep the edges at the same plan, according to FIG. 7, as the specific profile of the rounded core gets deformed in angles which are different from those expected.
Such situation raises the cost and lengthens the timespan of the constructions, for two workers are usually needed to fasten the rods with wire in order to have the edges at the same plan again.
The ROD WITH OCTAGONAL CORE PURPOSE-BUILT FOR CIVIL CONSTRUCTION, object of this patent, due to the octagonal profile of its core, makes itself as it is folded, either manually or industrially, not to form angles which make the hanger have the edges at distinct plans.
The FIG. 8 shows the octagonal profile (10) of the ROD WITH OCTAGONAL CORE PURPOSE-BUILT FOR CIVIL CONSTRUCTION (1) and the FIG. 9 shows its specific section (11), derived from its specific corrugated surface.
The FIG. 10 shows the system of the forces applied when folding the rods, from any profile of the section, both manually and industrially:—the rod (2) is placed in the correct position on the folding bolt by the fasteners (12) and (12 A); at this point it gets folded by the action of the force (14).
The FIG. 11 shows, in a frontal view, the results which are obtained; although the expected results are those of the straight defined by the points ABD, in the practice, folds which are distributed statistically by the angles formed by the straights ABC and ABE are obtained, and it is evident that in the formation of a squared-shaped hanger (4), four random dispersions like these are added, so that the hanger (4) does not result in co-planned, with the consequences which were pointed out.
The reason is obvious:—when it comes to folding a disc-like profile rod (2), the resistance against the fold force is the same in any direction due to the equality of the diameters; as to the octagonal profile rod (2), due to the parallelism of the opposite sides of such a polygon, the rod gets firm and correctly positioned on the folding bolt (13) by the fasteners (12) and (12 A), according to FIG. 12, and the area of the cut H . . . l, which corresponds to the polygon apothems, is smaller than F . . . G, which corresponds to its diagonals and is, thus, the area with the smallest resistance to the effort and it is where the fold effectively occurs, resulting in co-planned hangers (4).