Patent Description:
More specifically, the present invention proposes a connection system of prefabricated elements without bars protruding from the pieces and without concrete castings to be effected on site, capable of obtaining reinforcement continuity via mechanical coupling.

In the prefabrication of industrial, commercial and civil buildings, connections predominantly influence the static and seismic behaviour of the structural assembly. In particular, interlocking connections allow the flexibility to be reduced and increase the redundancy and robustness of the structure.

The document <CIT> discloses a pile splice section for a spliced prestressed concrete pile. The pile splice section includes a prestressed concrete element including a first end and a second end and a plurality of tendons that extend from the first end to the second end.

The document <CIT> discloses a modular building unit that includes a top end comprising a top surface, a bottom end comprising a bottom surface, a first plate assembly embedded in the top end, and a second plate assembly embedded in the bottom end.

The document <CIT> discloses a joint structure of civil engineering structures to prevent civil engineering structures from being cracked by a bolt tightening force when a joint is tightened with bolts to join the structures together.

The document <CIT> discloses a connection system for concrete parts which comprises doble-nut arrangements on the ends of first and second bars.

In the context of seismic actions, the requirement of structural ductility is also of fundamental importance for correct seismic behaviour in the post-elastic phase with energy dissipation.

In the state of the art, two types of connections are mainly known.

A first type is characterized by reinforcing bars that protrude from the prefabricated elements (male) and are introduced into specific recesses of the prefabricated elements (female). Following a concrete casting on site, the bars of the two elements overlap.

This first type of connection with anchoring bars that protrude from the prefabricated elements, however, has various drawbacks: (a) it requires on-site castings of the structurally most important parts which can hardly provide a concrete having an equal quality with respect to that of the prefabricated elements, usually produced with concrete mixing plants which guarantee considerably higher strengths than those normally obtained for on-site castings; (b) the bars that protrude from the prefabricated elements entail significant complications both in the production phase (for example the drilling of the formworks) and also when the elements are transported due to their anchoring and overlapping length (which can vary, for example, from <NUM> to <NUM> for bars with a diameter of <NUM>); (c) the elements require external shoring systems for maintaining the position in the temporary phase before the casting solidifies and for regulating the verticality/alignment; (d) the need for effecting concrete castings on site jeopardizes the possibility of producing and assembling highly industrialized elements, for example already provided with finishings and systems, which would be damaged or at least fouled by the casting operations.

A second type of connection uses mechanical connections for the reinforcement coupling. The most common type of these connections consists of an anchor bolt installed in an element that is inserted in a metal plate called "shoe" installed in the other element to be connected and anchored to it through overlapping bars having a significant length directly welded to the shoe.

Once the anchor bolt has been inserted into the shoe, the connection is closed through nuts and washers and the distance between the elements is filled with a sealing casting in high-strength anti-shrinkage mortar.

This second type of connection with mechanical connections, however, also has various drawbacks: (a) this system is not characterized by a good seismic structural behaviour in the post-elastic phase, as the structural ductility is limited by the small threaded length of the anchor bolt under the upper nut and as the energy dissipation is compromised by the cyclic necking phenomenon due to the distance between the nuts when the anchor bolt is plastically deformed; (b) the connection system has weldings in highly cyclically stressed areas of the structure; (c) the reduction in the concrete area in correspondence with the shoes leads to a weakening of the compression section; (d) the shoes are bulky and this limits the possibility of extensive use in reinforced concrete sections; (e) the quantity of steel used for these connections is considerable and consequently their cost and environmental impact are significant.

In light of the above, the undertaking of the present invention is to solve the drawbacks affecting the connection systems of prefabricated elements of the type known from the state of the art.

The objective of the present invention is to provide integrated connection systems for prefabricated elements with a simple and reliable configuration, which is sufficiently ductile for allowing its use even in seismic areas.

The above-mentioned undertaking, as also the above-mentioned and other objectives that will appear more evident hereunder, are achieved by a plurality of connection types for prefabricated elements based on an anchoring device according to the enclosed claim <NUM>.

Further characteristics of the connection systems of prefabricated elements according to the present invention are provided in the dependent claims, which also form an integral part of the present description.

Further characteristics and advantages will become more evident from the description of a preferred but non-exclusive embodiment of the connection system of prefabricated elements according to the present invention, illustrated by way of non-limiting example with the aid of the attached drawings wherein:.

With particular reference to <FIG>, the basic element of the connection system defined as the anchoring device according to the present invention, is shown as an example.

More specifically, <FIG> shows the anchoring device <NUM> according to the present invention inserted within a first structural element <NUM>, preferably made of concrete. The anchoring device <NUM> comprises a first bar <NUM> with continuous threading, which is inserted within said first structural element <NUM>.

Said bar is preferably made of high-strength steel, greater than the strength of the ribbed bars of reinforced concrete.

An embossed blind nut with a washer <NUM> is associated with one end 101a of said bar with continuous threading <NUM>, whereas a hexagonal or cylindrical joint nut <NUM> is associated with the other end 101b of said first bar <NUM>.

Ribbed bars <NUM> are also provided in adherence to the anchoring device <NUM> and also inserted within said structural element <NUM>. The traction actions in the cracked concrete phase are transmitted by the reinforced concrete ribbed bars <NUM> to the bar with continuous threading <NUM> in part by adherence and mostly through a diffusion cone (schematized by dots and dashes in cd) which has the embossed blind nut <NUM> at the top; they are subsequently transmitted by the bar with continuous threading <NUM> to the hexagonal or cylindrical joint nut <NUM> through a threaded connection.

The anchoring device according to the present invention as described so far, allows numerous advantages to be obtained with respect to systems of the type known from the state of the art.

Among these advantages, the following can be mentioned for example:.

With reference to <FIG>, a first non-claimed variant of the connection which uses the anchoring device <NUM> according to the present invention further comprises a connection bar <NUM> with continuous threading, of the same type as the bar <NUM>, which is screwed on site onto the hexagonal or cylindrical joint nut <NUM> and has a second embossed blind nut with a washer <NUM> at the end 105a.

Again from <FIG>, a blind knurled pipe <NUM> is also positioned in the second structural element <NUM> in a position which can accommodate the overlying connection bar <NUM>. The same bars <NUM> positioned in the element <NUM> are also present, adhering to the knurled pipe.

The connection system according to this first non-claimed variant of the present disclosure thus creates the connection between two structural elements <NUM>, <NUM>, for example an overlying pillar which must be connected to another underlying pillar, using the anchoring device <NUM>. The connection can be advantageously effected by inserting the connection bar <NUM> into the blind knurled pipe <NUM> and injecting into the knurled pipe, a special fast-setting mortar MA, high-strength (in any case not less than the strength of the concrete of the prefabricated elements) and anti-shrinkage.

The same actions must be transferred to these reinforcing bars <NUM> in the same way as for the anchoring device <NUM>, having, with the sealing casting reconstructed in the element <NUM>, the same transmission modes as the actions provided by the anchoring device of the element <NUM>.

The same pulling force considered previously thus passes from the hexagonal or cylindrical joint nut <NUM> to the bar with continuous threading <NUM> through a threaded connection; the action is then transmitted to the ribbed bars <NUM> positioned in the element <NUM> partly by adherence and mostly through a diffusion cone (schematized with dots and dashes in cd) which has the embossed blind nut <NUM> at the top. It can be seen that the diffusion cone exploits the adhesion of the knurled pipe <NUM> which is filled on site with high-strength anti-shrinkage mortar MA.

The connection of the structural elements <NUM> and <NUM> is thus obtained through the criterion, not of pure adherence of the reinforced concrete bars, but mainly based on the formation of diffusion cones cd of two specular anchoring devices, wherein the side surface of said diffusion cones is crossed by the ordinary reinforcing bars <NUM> to which the tension is transferred. This avoids having to connect bars protruding from the prefabricated components with a concrete casting.

In addition to the advantages of the anchoring device <NUM> according to the present invention already analyzed, the connection system according to this first non-claimed variant has other advantages, among which:.

A second non-claimed variant of the connection system, shown as an example in <FIG> and in the enlarged views <NUM> and 4A, provides for the use of the anchoring device <NUM> positioned in the lower structural element <NUM> in combination with a connection bar <NUM> with continuous threading, of the same type as the bar <NUM>, which is screwed on site to the hexagonal or cylindrical joint nut <NUM> and is inserted into at least one special anchoring plate <NUM> positioned in the overlying element <NUM>. The example of <FIG> shows two anchoring plates <NUM> spaced apart from each other and each positioned in correspondence with openings 300a recessed in the overlying element <NUM>.

The anchoring plate <NUM> has one or more substantially central openings into which the bar with continuous threading <NUM> screwed into the hexagonal or cylindrical joint nut <NUM>, inserted in the underlying element, and provided with a second nut <NUM>, is inserted. The anchoring plate <NUM> comprises two bushes <NUM> with truncated-conical threading welded to the side plates <NUM> and in which two reinforced concrete ribbed bars <NUM> with truncated-conical end threading are screwed, to which the tension is transferred as is the case for the reinforcing bars <NUM>. The threaded connection bar <NUM> with the upper nut <NUM> and the lower lock nut <NUM>, both equipped with a washer having an increased thickness <NUM>, is blocked in the centre of the anchoring plate.

The connection system according to this second variant allows the temporary support of the connection before the setting of the sealing mortar MA positioned between the lower structural element <NUM> and the overlying element <NUM> and in the opening of the anchoring plate <NUM> and the mechanical adjustment of the vertical position by acting on the lower nut of the bar with continuous threading <NUM> before the sealing casting. Furthermore, if installed in pairs with the same device, the alignment adjustment of the overlying element is also allowed.

Also in this connection, having oversized both the bar with continuous threading <NUM> and the anchoring plate <NUM> with the resistance hierarchy criterion, the tensile strength and ductility are entrusted to the reinforced concrete ribbed bars <NUM>, connected to the bushes <NUM> through a truncated-conical threading that minimizes weakening in the interface section.

The advantages of the connection device <NUM> are the following:.

Some application examples of the connection system are provided hereunder.

With reference to <FIG>, this illustrates a connection between a pillar, for example having dimensions of 60x60 cm, and the underlying foundation. The section at the base of the pillar contains at each of the four vertices, three connections according to the first variant (first type) to the underlying foundation, and in the centre of the four sides, a further four connection systems according to the second variant (second type) described above.

The four connections of the second type are used for adjusting the verticality and alignment of the pillar acting from below. The pillar rests on a central spacer on which it unloads its weight in a transitory phase.

The four connection bars are sized for the forces of wind or earthquake in transitory phase and keep the pillar blocked for allowing the injection and subsequent maturation of special mortar both in the knurled pipes of the first connection embedded with a template in the foundation and also for giving continuity of concrete between the upper pillar and foundation or lower pillar.

In addition to the advantages listed above for the anchoring device and for the two connection systems, a rapid and safe connection between pillar and foundation is obtained by simultaneously using the two connection systems according to the two non-claimed variants.

With reference to <FIG>, the wall-foundation or wall-wall connection is obtained by proposing in the two end areas of the wall, the presence, in a section of <NUM> x <NUM>, of four connections of the first type and two connections of the second type. By acting on the nut and lock nut of the four mechanical connections of the second type, the verticality/alignment of the wall can be adjusted, keeping it blocked to allow the injection of special mortar into the connections of the first type.

With reference to <FIG>, a connection is obtained between a bracket and a shear beam also called "pinning", using a connection system of the first type in which the blind knurled pipe <NUM> is inserted in the beam T and the anchoring device <NUM> in the bracket M.

In this application, the connection bar is not subjected to traction but only to shearing, so that the bar <NUM> can have a reduced length, in order to be inserted in a bracket having a reduced height.

Also in the case of pinning, it is important to effect the connection without bars protruding from the bracket, which would be difficult to set up and manage.

With reference to <FIG>, these show the implementation, regardless of a possible "pinning", of an interlocked pillar-beam connection using the connection system according to the second variant (second type) described herein. The main advantage of this connection lies in the fact that it can be effected with a fully assembled construction with the permanent loads acting on beams hinged to the pillars or "pinned" to these.

This connection, which provides for a connection to both the upper and lower edge, is therefore only subjected to stress by variable loads and in the presence of horizontal actions (seismic or wind) which cause the onset, at the upper and lower edge, of equal moments of both compression and traction in the presence of a connection that ensures a symmetrical hysteresis cycle obtained by blocking the nut and lock nut on the anchoring plate.

The design is interesting in high ductility that can be obtained without renouncing the traditional details of the beam head reinforcements sized on the vertical loads, by arranging the sheaths <NUM> for a predetermined length on the ribbed bars of reinforced concrete <NUM> behind their truncated-conical threading so as to ensure the loss of adhesion between the reinforced concrete ribbed bars and concrete and extend the yield strength under seismic actions at least to the length of the sheath itself.

This possibility of creating a joint that is engaged only for horizontal actions is a significant resource of dry prefabrication that cannot be obtained with the frame structures produced with concrete cast on site in the node. An embodiment of the connection system according to the present invention is also proposed, shown by way of example in <FIG> and <FIG>, in which the same elements and with the same functions with respect to those previously illustrated have the same reference numbers. In this case, the system provides for the use of an anchoring device <NUM> positioned in the lower structural element <NUM> combined with a connection bar <NUM> with continuous threading, of the same type as the bar <NUM>, which is screwed on site to the hexagonal joint nut or cylindrical <NUM> and is inserted into a further embodiment of an anchoring plate <NUM> positioned in the overlying element <NUM>.

The anchoring plate <NUM> has one or more substantially central openings into which the bar with continuous threading <NUM> screwed into the hexagonal or cylindrical joint nut <NUM> inserted in the underlying element <NUM> and provided with a second nut <NUM>, is inserted. The anchoring plate <NUM> in this example can be produced in a single piece and comprises two or more saddle shapes <NUM> around which two or more ribbed bars of reinforced concrete <NUM> are wound which can be identical to the bars inserted in the lower structural element <NUM>. The threaded connection bar <NUM> is blocked in the centre of the anchoring plate, with upper nut <NUM> and lower lock nut <NUM>, both equipped with perforated plates, the upper <NUM> and lower <NUM>, possibly having a lower thickness.

The connection system according to this embodiment of the present invention allows the temporary support of the connection before the setting of the sealing mortar MA and the mechanical adjustment of the vertical position by acting on the lower nut of the bar with continuous threading <NUM> before the sealing casting. Furthermore, if installed in pairs with the same device, the alignment adjustment of the overlying element is also allowed.

Also in this connection, having oversized both the bar with continuous threading <NUM> and the anchoring plate <NUM> with resistance hierarchy criterion, the tensile strength and ductility are entrusted to the ribbed bars of reinforced concrete <NUM>, connected to the anchoring plate <NUM> through the saddle shapes <NUM>.

The advantages of the connection device with anchoring plate <NUM> are the following:.

the conformation of the current bars are completely identical to each other, in terms of both shape and diameter.

Claim 1:
A connection system for prefabricated elements for joining two structural elements (<NUM>,<NUM>) in concrete or equivalent material, comprising an anchoring device (<NUM>) in turn comprising at least a first bar with continuous threading (<NUM>) configured for being inserted within a first (<NUM>) of said two structural elements (<NUM>,<NUM>), a first embossed nut (<NUM>) being associated with a first end (101a) of said first bar (<NUM>) and a joint nut (<NUM>) being associated with a second end (101b) of said first bar (<NUM>), a second bar with continuous threading (<NUM>) which is adapted to be screwed, on site, to said joint nut (<NUM>) the connection system further comprising an anchoring plate (<NUM>) with one or more substantially central openings, wherein, in an installed state of the connection system, said second bar (<NUM>) is inserted into the at least one opening of said anchoring plate (<NUM>) suitable to be positioned in the second (<NUM>) of said two structural elements (<NUM>,<NUM>), said anchoring plate (<NUM>) comprises side saddle shapes (<NUM>) within which reinforced concrete ribbed bars (<NUM>) are enveloped, said ribbed bars (<NUM>) being inserted in said structural elements (<NUM>,<NUM>), wherein the second bar (<NUM>) is blocked in the centre of the anchoring plate (<NUM>) by a lower lock nut (<NUM>) and a second, upper nut (<NUM>).