WO2021019368A1

WO2021019368A1 - Dry connection system of prefabricated elements

Info

Publication number: WO2021019368A1
Application number: PCT/IB2020/056890
Authority: WO
Inventors: Bruno Alberto DAL LAGO
Original assignee: Dlc Consulting S.R.L.
Priority date: 2019-07-26
Filing date: 2020-07-22
Publication date: 2021-02-04
Also published as: ES2953793T3; EP4004302A1; EP4004302B1; FI4004302T3; EP4223949A1

Abstract

The present invention relates to a connection system of prefabricated elements used in the construction of industrial, commercial and civil buildings. More specifically, the present invention proposes a connection system of prefabricated elements by coupling based on the combined formation mechanisms of extraction cone and adhesion. The connection can be oversized with respect to the reinforcing ribbed bars of reinforced concrete with the resistance hierarchy criterion, in order to ensure ductile capacities and stable energy dissipation and consequently the use of structures in seismic areas with traditional design methods. The connection system of prefabricated elements according to the invention is characterized in that it comprises an anchoring device which provides for the use of high-strength bars with continuous threading and in that all the elements of the anchoring device, when the device is assembled, are completely inserted in the castings of the prefabricated concrete elements so that there are no mechanical parts protruding from the encumbrance of the elements themselves. The use of a special element also allows the support of the loads in the transitory phase and the mechanical adjustment of the verticality/alignment of the overlying structural element.

Description

DRY CONNECTION SYSTEM OF PREFABRICATED ELEMENTS

k k k

FIELD OF THE INVENTION

The present invention relates to a connection system of prefabricated elements used in the construction of industrial, commercial and civil buildings.

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.

STATE OF THE ART

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.

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 100 to 150 cm for bars with a diameter of 25 mm) ;

(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.

SUMMARY OF THE INVENTION

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 1.

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.

LIST OF FIGURES

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: figure 1 shows a schematic view of the anchoring device according to the present invention;

figure 2 shows a schematic overall view of the connection system according to a first embodiment of the present invention which uses the anchoring device of figure 1, the system being in a disassembled condition;

figure 2A shows the connection system of figure 2 in an assembled condition;

figure 2B shows a view from above of the connection system of figure 2A;

figure 3 shows a schematic overall view of the connection system again comprising the anchoring device of figure 1 but according to a second embodiment of the present invention, the system being in a disassembled condition;

figure 3A shows the system of figure 3 in an assembled configuration;

figure 3B shows a view from above of the system of figure

3A;

figure 4 shows a side view of a detail of the plate of the system of figure 3A;

figure 4A shows, in a view from above, the detail of figure

4;

figure 5 shows, in a schematic view, a view from above of an overlying pillar (on the left in the figure) and an underlying pillar (on the right in the figure) wherein a plurality of connection systems according to the first and second embodiment of the present invention, are used;

figure 6 and figure 6A show, in a side view and in a view from above, respectively, a second application of the connection system according to the present invention;

figure 7 shows a side view of a further pillar-beam application of the connection system according to the present invention;

figures 8 and 8A show, in a view from above and in a side view, respectively, further possible applications of the connection system according to the present invention for the construction of pillar-beam connections;

figures 9A, 9B and 9C show a schematic overall view of the connection system again comprising the anchoring device of figure 1 but according to a third embodiment of the present invention, the system being in an assembled condition; in particular figure 9A shows the system in a side view in an assembled configuration, figure 9B shows a view from above of the system of figure 9A; and figure 9C shows a side view from a different side;

figure 10 shows a side view of a detail of the plate of the system of figure 9A;

figure 10A shows, in a view from above, the detail of figure

10;

- figures 11 and 11A show, in a schematic side view and in a view from above, a further application of the connection system of the present invention;

figures 12, 13, 14 and 15 show two perspective views, a side view and a view from above of an anchoring plate according to figures 9A, 9B, 9C, 10 and 10A of the present invention.

DE TAILED DESCRIPTION OF THE INVENTION

With particular reference to Figure 1, the basic element of the connection system defined as the anchoring device according to the present invention, is shown as an example.

More specifically, figure 1 shows the anchoring device 100 according to the present invention inserted within a first structural element 10, preferably made of concrete. The anchoring device 100 comprises a first bar 101 with continuous threading, which is inserted within said first structural element 10.

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 102 is associated with one end 101a of said bar with continuous threading 101, whereas a hexagonal or cylindrical joint nut 103 is associated with the other end 101b of said first bar 101.

Ribbed bars 104 are also provided in adherence to the anchoring device 100 and also inserted within said structural element 10. The traction actions in the cracked concrete phase are transmitted by the reinforced concrete ribbed bars 104 to the bar with continuous threading 101 in part by adherence and mostly through a diffusion cone (schematized by dots and dashes in cd) which has the embossed blind nut 102 at the top; they are subsequently transmitted by the bar with continuous threading 101 to the hexagonal or cylindrical joint nut 103 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 :

a) as the bar with continuous threading 101 is made of steel with a greater tensile strength than normal ribbed bars of reinforced concrete, it ensures a high strength of the joint and, if correctly sized, a uniformity of the strength of the bars which guarantees ultimate ductility with yield which involves a considerable plasticization length of the joint subjected to traction;

b) the threading guarantees high adherence to the concrete;

c) the components of the anchoring device 100 are all completely inserted inside the prefabricated element 10, from which no bar protrudes;

d) the length of the bar 101, anchored by protrusion which creates a diffusion cone of the actions, is considerably less than the anchoring length of the bars of reinforced concrete that would be necessary for obtaining an anchorage by adherence or by overlapping according to the state of the art.

With reference to Figure 2, a first embodiment of the connection according to the present invention which uses the anchoring device 100 according to the present invention further comprises a connection bar 105 with continuous threading, of the same type as the bar 101, which is screwed on site onto the hexagonal or cylindrical joint nut 103 and has a second embossed blind nut with a washer 106 at the end 105a.

Again from Figure 2, a blind knurled pipe 107 is also positioned in the second structural element 20 in a position which can accommodate the overlying connection bar 105. The same bars 104 positioned in the element 10 are also present, adhering to the knurled pipe.

The connection system according to this first embodiment of the present invention thus creates the connection between two structural elements 10, 20, for example an overlying pillar which must be connected to another underlying pillar, using the anchoring device 100. The connection can be advantageously effected by inserting the connection bar 105 into the blind knurled pipe 107 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 104 in the same way as for the anchoring device 100, having, with the sealing casting reconstructed in the element 20, the same transmission modes as the actions provided by the anchoring device of the element 10.

The same pulling force considered previously thus passes from the hexagonal or cylindrical joint nut 103 to the bar with continuous threading 105 through a threaded connection; the action is then transmitted to the ribbed bars 104 positioned in the element 20 partly by adherence and mostly through a diffusion cone (schematized with dots and dashes in cd) which has the embossed blind nut 106 at the top. It can be seen that the diffusion cone exploits the adhesion of the knurled pipe 107 which is filled on site with high-strength anti-shrinkage mortar MA .

The connection of the structural elements 10 and 20 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 104 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 100 according to the present invention already analyzed, the connection system according to this first embodiment has other advantages, among which:

(a) the connection does not require castings on site but only an injection of mortar with a reduced volume that does not create dirt, which can classify the system according to the present invention as a dry connection (without concrete casting on site) ;

(b) an advantage obtained with the connection system of prefabricated elements according to the present invention consists in the fact that the connection operates both under compression and in traction, thus ensuring a symmetrical hysteresis cycle, as is required in seismic areas, and an emulative behaviour of the reinforced concrete structures cast on site;

(c) the connection allows production and assembly tolerances;

(d) among the advantages of the system according to the present invention, there is also the fact that the connection is effected with a low volume of steel and with easily available serial components, thus reducing the environmental impact of the connection and its cost.

A second embodiment of the connection system according to the present invention, shown as an example in Figures 3, 3A and 3B and in the enlarged views 4 and 4A, provides for the use of the anchoring device 100 positioned in the lower structural element 10 in combination with a connection bar 105 with continuous threading, of the same type as the bar 101, which is screwed on site to the hexagonal or cylindrical joint nut 103 and is inserted into at least one special anchoring plate 300 positioned in the overlying element 20. The example of figure 3B shows two anchoring plates 300 spaced apart from each other and each positioned in correspondence with openings 300a recessed in the overlying element 20.

The anchoring plate 300 has one or more substantially central openings into which the bar with continuous threading 105 screwed into the hexagonal or cylindrical joint nut 103, inserted in the underlying element, and provided with a second nut 108, is inserted. The anchoring plate 300 comprises two bushes 301 with truncated-conical threading welded to the side plates 302 and in which two reinforced concrete ribbed bars 303 with truncated-conical end threading are screwed, to which the tension is transferred as is the case for the reinforcing bars 104. The threaded connection bar 105 with the upper nut 108 and the lower lock nut 304, both equipped with a washer having an increased thickness 305, is blocked in the centre of the anchoring plate.

The connection system according to this second embodiment of the present invention allows the temporary support of the connection before the setting of the sealing mortar MA positioned between the lower structural element 10 and the overlying element 20 and in the opening of the anchoring plate 300 and the mechanical adjustment of the vertical position by acting on the lower nut of the bar with continuous threading 105 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 105 and the anchoring plate 300 with the resistance hierarchy criterion, the tensile strength and ductility are entrusted to the reinforced concrete ribbed bars 303, connected to the bushes 301 through a truncated-conical threading that minimizes weakening in the interface section.

The advantages of the connection device 300 are the following :

(a) the connection is totally mechanical, dry, without protrusions from the elements;

(b) the element allows, in addition to reinforcement continuity, the vertical adjustment of the upper element from below, which also allows the adjustment of all degrees of freedom by inserting a pair of connections;

(c) the connection is reversible, as a possible disassembly can be effected;

(d) the connection operates both under compression and in traction, thus ensuring a symmetrical hysteresis cycle, as is required in seismic areas;

(e) the connection allows for large production and assembly tolerances .

Some application examples of the connection system according to the present invention are provided hereunder.

EXAMPLE 1 : Pillar-foundation or pillar-pillar connection, with simultaneous use of two connection systems according to the present invention.

With reference to Figure 5, 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 embodiment of the present invention (first type) to the underlying foundation, and in the centre of the four sides, a further four connection systems according to the second embodiment of the present invention (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 embodiments of the present invention.

EXAMPLE 2 : Wall-foundation or wall-wall connection with simultaneous use of both connection systems according to the two embodiments shown.

With reference to Figures 6 and 6A, 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 25 x 90 cm, 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.

EXAMPLE 3 : Connection by "pinning" using a connection system of the first type, i.e. according to the first embodiment described herein of the present invention.

With reference to Figure 7, 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 107 is inserted in the beam T and the anchoring device 100 in the bracket M .

In this application, the connection bar is not subjected to traction but only to shearing, so that the bar 101 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.

EXAMPLE 4 : Pillar-beam connection for creating joints using a connection system of the second type, i.e. according to the second embodiment.

With reference to Figures 8 and 8A, these show the implementation, regardless of a possible "pinning", of an interlocked pillar-beam connection using the connection system according to the present invention according to the second embodiment (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 306 for a predetermined length on the ribbed bars of reinforced concrete 303 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.

A third embodiment of the connection system according to the present invention is also proposed, shown by way of example in Figures 9A, 9B, 9C and 10 and 10A, 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 100 positioned in the lower structural element 10 combined with a connection bar 105 with continuous threading, of the same type as the bar 101, which is screwed on site to the hexagonal joint nut or cylindrical 103 and is inserted into a further embodiment of an anchoring plate 1300 positioned in the overlying element 20.

The anchoring plate 1300 has one or more substantially central openings into which the bar with continuous threading 105 screwed into the hexagonal or cylindrical joint nut 103 inserted in the underlying element 10 and provided with a second nut 108, is inserted. The anchoring plate 1300 in this example can be produced in a single piece and comprises two or more saddle shapes 1301 around which two or more ribbed bars of reinforced concrete 1104 are wound which can be identical to the bars inserted in the lower structural element 10. The threaded connection bar 105 is blocked in the centre of the anchoring plate, with upper nut 108 and lower lock nut 304, both equipped with perforated plates, the upper 305 and lower 305, possibly having a lower thickness.

The connection system according to this third 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 105 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 105 and the anchoring plate 1300 with resistance hierarchy criterion, the tensile strength and ductility are entrusted to the ribbed bars of reinforced concrete 1104, connected to the anchoring plate 1300 through the saddle shapes 1301.

The advantages of the connection device with anchoring plate 1300 are the following:

(b) the element allows, in addition to reinforcement continuity, the verticality adjustment of the upper element from below, which also allows the verticality adjustment by inserting a pair of connections;

(c) the connection is reversible, as a possible disassembly can be effected;

(d) the connection allows for ample production and assembly tolerances ;

(e) weakening of the bars is avoided with a truncated-conical threading;

(f) mechanical machining of the bars which requires special processing and labour is avoided;

(g) for diameters not exceeding 14 mm (for example cp12 ) , bars with improved adherence can be adopted, taken from rolls using machines that straighten and bend, thus totally avoiding any waste in the cutting of straight bars supplied with a predetermined length; (h) in the combined use of the first and third connection systems, the conformation of the current bars are completely identical to each other, in terms of both shape and diameter.

The present invention has been described, for illustrative but non-limiting purposes, with examples of use of the connections wherein the anchoring device object of the first claim has been used, but it should be understood that variations and/or modifications to the connections or different applications can be applied by skilled persons in the construction field, without thereby being excluded from the relative protection scope, as defined in the enclosed claims.

Claims

1. A connection system of prefabricated elements, in particular for joining two structural elements (10,20) in concrete or equivalent material, comprising an anchoring device (100) in turn comprising at least a first bar with continuous threading (101) configured for being inserted within a first (10) of said two structural elements (10,20), a first embossed nut (102) being associated with a first end (101a) of said first bar (101) and a joint nut (103) being associated with a second end (101b) of said first bar (101), characterized in that it further comprises a second bar with continuous threading (105), a second embossed nut (106) being associated with a first end (105a) of said second bar (105), said second bar (105) being configured for being inserted within a second (20) of said two structural elements (10,20), a blind knurled pipe (107) being further configured for being inserted in said second structural element (20) to receive said second bar

(105) .

2. The connection system according to one or more of the previous claims, characterized in that said joint nut (103) is hexagonal or cylindrical.

3. The connection system according to claim 1, characterized in that it further comprises an anchoring plate (300,1300) suitable for receiving one or more bars with continuous threading (101,105) .

4. The connection system of prefabricated elements according to one or more of the previous claims, characterized in that said first bar (101) and, when present, second (105) bar, are made of high-strength steel.

5. The connection system of prefabricated elements according to the previous claim, characterized in that said anchoring plate (300) further comprises side plates (302) to which bushes (301) with a truncated-conical threading are connected, inside which ribbed bars of reinforced concrete (303) are screwed with a truncated-conical end threading to which the tension is transferred.

6. The connection system of prefabricated elements according to one or more of the previous claims, characterized in that it further comprises a plurality of reinforcing bars (104) suitable for being inserted within one or more of said structural elements (10,20) .

7. The connection system of prefabricated elements according to the previous claim, characterized in that when the system is assembled, said reinforcing bars (104) are within said first structural element (10) positioned adhering to said first bar (101), and within said second structural element (20) positioned adhering to said blind knurled pipe (107), when present .

8. The connection system of prefabricated elements according to the previous claim, characterized in that it comprises at least one pair of anchoring devices (100) connected to said anchoring plate (300) .

9. The connection system of prefabricated elements according to the previous claim, characterized in that sheaths (106) are installed on the ribbed bars of reinforced concrete (303) behind their truncated-conical end threading connected to said anchoring plate (300) of anchoring devices (100) .

10. A method for connecting prefabricated structural elements, comprising the following steps:

providing a connection system according to claim 1;

inserting the device of said connection system (100) within the casting of said two structural elements (10,20), in particular by positioning said first bar (101) and said joint nut (103) within the casting of said first structural element (10), and said second bar (105) and said blind knurled pipe (107) being positioned within the casting of said second structural element (20), so that the elements of said connection system remain completely inside said structural elements;

inserting a plurality of reinforcing bars (104) into each of said structural elements (10,20);

solidifying the castings of said two structural elements (10,20) in concrete;

connecting said structural elements (10,20) together by tightening said second bar (105) within said hexagonal or cylindrical joint nut (103) previously connected to said first bar (101);

injecting a fluid quick-setting mortar MA, anti-shrinkage and high-strength not less than that of the concrete of the prefabricated elements, into the spacing between the prefabricated elements, so as to spread said mortar MA also inside the blind knurled pipes (107) so that said reinforcing bars (104) are immersed in said mortar MA;

waiting for the mortar MA to solidify.

11. The method for connecting prefabricated structural elements according to the previous claim, wherein said joint nut (103) is hexagonal or cylindrical.

12. The connection system of prefabricated elements according to the previous claim 3, characterized in that said anchoring plate (1300) comprises side saddle shapes (1301) within which reinforced concrete ribbed bars (1104) are enveloped, inserted in said structural elements (10,20) to which the tension is transferred.

13. The connection system of prefabricated elements according to the previous claim, characterized in that it comprises at least one pair of anchoring devices (100) connected to said anchoring plate (1300) .

14. The connection system of prefabricated elements according to the previous claim 11 or 12, characterized in that two anchoring plates (1300) are provided.

15. The connection system of prefabricated elements according to the previous claim, characterized in that sheaths (306) are installed on the ribbed bars of reinforced concrete (1104) behind their curvature for connection to said anchoring plate (1300) of anchoring devices (100) .