EP0379141A1 - Concrete reinforcement connection - Google Patents

Abstract

The connection between at least two lengths of a concrete reinforcement (1, 2a) is designed as a sleeveless screw connection with a conical threaded portion (6) on one length engaging in a conical threaded bore (4) in the other length, and the concrete reinforcement (1) forming one length has, at least in the region of the connection, a diameter (D) which is greater than the diameter (d) of the concrete reinforcement (2a) forming the other length. <IMAGE>

Description

The invention relates to a sleeve-free connection of at least two lengths of boton steel.

Screwed reinforcing steel connections or reinforcing steel joints using sleeves designed as threaded bushings are known. These connections are not only complex to manufacture and use, but also have the disadvantage that the sleeves used have an outer diameter which is considerably larger than the effective cross section of the reinforcing steel, so that problems arise in many cases provide sufficient concrete coverage.

The invention has for its object to show a screwed reinforcing steel connection that can be manufactured easily and inexpensively.

To solve this problem, a reinforcing steel connection (reinforcing steel joint) according to the invention is designed in accordance with the characterizing part of patent claim 1.

In the connection according to the invention, the conical thread section (with external thread) is formed directly at one end of the other length of the reinforcing steel, and preferably by applying or cutting the thread with a suitable thread cutting device or with a suitable tool, which can also be used at the place of use ( Construction site) is available and can be handled easily and conveniently there. Cutting the conical threaded piece to the other length of the reinforcing steel only at the place of use (construction site) also has the advantage that this other length of the reinforcing steel can be optimally adapted to the respective requirements on the construction site.

The conical threaded hole provided on one length of the reinforcing steel is likewise made directly in one end of this length of the reinforcing steel, preferably with a suitable threading device or machine tool (e.g. lathe or automatic lathe).

The other length provided with the threaded attachment has a diameter which is smaller than the diameter of the length of the reinforcing steel provided with the associated threaded bore, the diameters preferably being chosen such that they are adjacent to one another in a predetermined row of reinforcing steel diameters.

In one possible embodiment of the invention, an adhesive or soldered connection is used in addition to the screw connection. This additional adhesive or soldered connection initially prevents the screw connection from loosening, but acts especially when the connection is subjected to dynamic loads, in that the screw connection "knocks out", i.e. against the signs of fatigue there and keeps the screw connection largely free of dynamic forces, so that the connection as a whole, i.e. through the combination of screw connection and adhesive or Soldered connection has a high load capacity and in particular also has high fatigue strength.

At least that length of the reinforcing steel which has the recess provided with the nut thread consists of a heat-treated reinforcing steel, ie of a reinforcing steel which is produced by the so-called "Temcore process" and has a harder outer cross-sectional area and a softer one enclosed by this cross-sectional area Core. The harder cross-sectional area of greater strength is also located radially outside the recess having the nut thread section, ie the latter is enclosed by the harder cross-sectional area, so that this results in optimal conditions with regard to the transmission of force, in particular also with regard to the transmission of tensile force as well as torque transmission and thus an optimal load-bearing capacity of the socket-free, screwed reinforcing steel connection.

The screw connection according to the invention can be used in a particularly advantageous manner as connection reinforcement or reinforcement connection.

Developments of the invention are the subject of the dependent claims.

• Fig. 1 in schematischer Darstellung und im Schnitt eine bevorzugte Ausführung der erfindungsgemäßen Schraub­verbindung zwischen zwei Längen eines Betonstahls;
• Fig. 2 die Betonstahlverbindung nach Fig. 1 in ihrer Aus­bildung als Bewehrungsanschluß;
• Fig. 3 einen Schnitt durch zwei aneinander anschließende Betonbauteile;
• Fig. 4 in schematischer Darstellung eine Beton-Armierung, bestehend aus drei aneinander anschließenden und jeweils durch eine Schraubverbindung miteinander verbundenen Längen aus Betonstahl mit unterschied­lichem Durchmesser;
• Fig. 5 in schematischer Darstellung und teilweise im Schnitt eine weitere muffenlose Schraubverbindung zwischen zwei Längen eines Betonstahls gemäß der Erfindung;
• Fig. 6 die verbindung nach Fig. 1 in vergrößerter Dar­stellung;
• Fig. 7 in Einzeldarstellung das Profil des Gewindes einer Verbindung gemäß der Erfindung.

The invention is explained below with reference to the figures using exemplary embodiments. Show it:

• Fig. 1 in a schematic representation and in section a preferred embodiment of the screw connection according to the invention between two lengths of a reinforcing steel;
• FIG. 2 shows the reinforcing steel connection according to FIG. 1 in its training as a reinforcement connection;
• 3 shows a section through two adjoining concrete components;
• 4 shows a schematic representation of a concrete reinforcement consisting of three adjoining lengths of reinforcing steel of different diameters, each of which is connected by a screw connection;
• Fig. 5 in a schematic representation and partly in section a further sleeve-less screw connection between two lengths of a reinforcing steel according to the invention;
• Fig. 6 shows the connection of Figure 1 in an enlarged view.
• Fig. 7 in individual representation, the profile of the thread of a connection according to the invention.

In Fig. 1, 1 and 2a are two reinforcing bars, of which at least the reinforcing steel 1 is a heat-treated, e.g. Reinforced steel produced by the so-called "TEMPCORE process" and accordingly has an outer cross-sectional area 3 of particularly high strength.

In one end of the reinforcing steel 1 is a truncated cone-shaped recess 4 with its axis coaxial with the longitudinal axis L of the reinforcing steel 1, which is provided with an internal thread 5 and thus forms a truncated conical or tapered threaded hole.

The reinforcing steel 2a is provided at one end with a frustoconically tapering extension 6, the axis of which lies coaxially with the axis of the reinforcing steel 2a. The fitting 6 fitting into the recess 4 is provided on its outer surface with an external thread 7, so that the fitting 6 forms a truncated cone-shaped threaded piece which can be screwed into the recess 4 to connect the two reinforcing steels 1 and 2a or the two lengths of these reinforcing steels .

In the embodiment shown, the circumferential or lateral surface of the extension 6 and accordingly also the frustoconical or conical circumferential surface of the recess 4 form an angle a with the longitudinal axis L of the respective reinforcing steel 1 or 2. The reinforcing steel 1 has the larger diameter D and the reinforcing steel 2a the smaller diameter d, which also corresponds to the diameter of the extension 6 at its base.

The conical or frusto-conical screw connection formed by the recess 4 and in the extension 6 has a number of advantages, including the advantage that, despite a cross section D which is only slightly smaller than the cross section D, a sleeve-free screw connection is possible, which is also possible at the connection point between the reinforcing bars 1 and 2a does not have an enlarged outer diameter and so that it does not pose the problems that often arise with regard to the concrete cover in steel screw connections using sleeves. Furthermore, it is ensured by the conical screw connection that with optimal cross-sectional conditions also for a tensile force transmission at the connection point between the reinforcing bars 1 and 2a, these reinforcing bars mesh with one another on the threads 5 and 7 over a relatively large area and also the diameter of the recess 4 and the extension 6 over the entire connection area is relatively large.

The smaller diameter d results in the connection according to FIG. 1, particularly favorable conditions, in particular also with regard to the static and dynamic load capacity.

Fig. 2 shows a sleeve-less screw connection, in which the reinforcing bars 1 and 2a form parts of a connecting reinforcement or a reinforcement connection 8, which is used where a concrete component first created, for example on a concrete wall 9, another concrete component, for example one concrete wall 10 extending at right angles to the concrete wall 9 is to be connected (FIG. 3). The reinforcement connection 8 is used in such a way that the length of the reinforcing steel 1 with the larger diameter D is embedded in the concrete of this concrete wall in the manufacture of the concrete wall 9 in such a way that, after stripping the concrete wall 9, the end of the reinforcing steel 1 provided with the recess 4 is accessible. The reinforcing steel 1 forms the anchoring part of the connecting reinforcement or the reinforcement connection 8 to be arranged in the concrete wall 9.

After stripping the concrete wall 9, the reinforcing steel 2a is screwed into the recess 4 with the attachment 6 and then embedded or integrated as a connecting part of the connection reinforcement or the reinforcement connection 8 in the concrete there when the concrete wall 10 is being produced. In order to prevent concrete from penetrating into the recess 4 of the reinforcing steel 1 when the concrete wall 9 is being produced, it is Reinforcing steel with its end provided with the recess 4, for example, housed in the interior 11 of a box-like storage element 12, in the same way as the corresponding ends of further reinforcing bars 1. All reinforcing bars 1 then protrude outwards through a common floor 13 of the storage element 12, as in the case of Reinforcement connections for the anchoring parts is known per se. After stripping the concrete wall 9, the storage element 12 is opened by removing a cover 14, so that the ends of the reinforcing bars 1 provided with the recesses 4 are then accessible for screwing in a reinforcing steel 2a.

Since the incorporation of the reinforcing steel 1 or 2a in the concrete for a given profile essentially depends on the area of the reinforcing steel 1 or 2a enclosed by the concrete and is therefore not only proportional to the length but also proportional to the diameter D or d of the respective reinforcing steel , The length x of the reinforcing steel 1 can be chosen to be significantly smaller than the length X of the reinforcing steel 2a. The use of the reinforcing steel 1 as an anchoring part thus has the advantage that despite the necessary adjustment of the length x of the reinforcing steel to the thickness of the concrete wall 9 in the form that the length x is less than the thickness of the concrete wall 9, an optimal integration of the elements of connecting reinforcement formed by the concrete steels 1 and 2a in the concrete walls 9 and 10 and thus an optimal force transmission in the area of the connecting reinforcement can be achieved. Since the reinforcing steel 2a forming the connecting part extends in the concrete wall 10 essentially parallel to the surface sides of this concrete wall, the length X of the reinforcing steel 2a is practically uncritical. Overall, the reinforcement connection 8 formed by the reinforcing steels 1 and 2a also has the advantage that, with simple handling and manufacture, in particular also without the use of threaded sockets, the bending of bent connecting parts, which severely affects the fatigue strength of reinforcing steels, is not necessary. Of course, it is also possible to use other suitable means instead of the storage element 12 to be provided, through which the recess 4 of the respective length of the reinforcing steel 1 is accessible after the shuttering of the concrete component first created, ie the concrete wall 9.

As shown in FIG. 4, it is in particular also possible with the screw connection according to the invention to optimally adapt the steel cross section or the cross section of a concrete reinforcement to the moments in a concrete component. 4, 15 is a concrete component in the form of a concrete beam or beam. 16 generally designates a reinforcing steel arrangement provided in the concrete component 15 and forming part of the reinforcement there, which extends in the longitudinal direction of the concrete component 15. According to the assumed torque curve with a maximum lying in the middle of the concrete component 15, the reinforcing steel arrangement 16 consists of an average length 16 'of the reinforcing steel 1 with the larger diameter D. At the two ends of the length 16' is corresponding via a socket-free, conical screw connection 1 is connected to a length 16˝ of the reinforcing steel 2a with the smaller diameter d.

In Fig. 5, 101 and 102 are two reinforcing bars, of which at least the reinforcing steel 101 is a heat-treated, e.g. Reinforced steel manufactured according to the so-called "Tempcore process" and accordingly has an outer cross-sectional area of particularly high strength. In one end of the reinforcing steel 101 there is a recess with its axis coaxial with the longitudinal axis of this reinforcing steel, which is composed of a circular-cylindrical section 103 and an inner conical section 104, the end of the section having the smaller diameter 104 forms the bottom of the recess formed by the sections 103 and 104.

The reinforcing steel 102 extends into the aforementioned recess with one end, ie in the region of this one end the reinforcing steel 102 has a circular-cylindrical section 105, which is received by the partial section 103, and also with a frustoconical section 106 is provided, which has an external thread and with which the reinforcing steel 102 is screwed into the internal thread of the section 104. At section 105, the reinforcing steel 102 has an outside diameter that is equal to the inside diameter of the section 103. 5, the reinforcing steel 102 has an outer diameter d that is smaller than the outer diameter D of the reinforcing steel 101 anyway, the reinforcing steel 102 at section 105 is only slightly turned on its outer surface in order to be there otherwise on the reinforcing steel 102, but also to remove ribs 107 provided on the reinforcing steel 101 and to achieve an outer cross section for the section 105 that fits as precisely as possible into the section 103. In the area of the actual screw connection between the section 104 and the section 106, but especially in the area of the section 103 and section 105, the two reinforcing bars 101 and 102 are connected to one another using a suitable adhesive. This additional adhesive connection has the advantage that it not only effectively counteracts any loosening of the screw connection, but also achieves a substantial improvement or increase in the fatigue strength of the reinforcing steel connection. Most of the dynamic loads between the two reinforcing bars 101 and 102 are already transferred through the adhesive connection. Furthermore, the type of connection described also results in a significant improvement in the breaking and bending strength, in particular also in that both through the section 103 of the recess of the reinforcing steel 101 and through the section 105 of the reinforcing steel 102 engaging in this section 103 Interlocking reinforcing bars over a relatively long length. The axial length of the section 104 or the section 105 is, for example, 20 mm.

In the reinforcing steel connection according to FIG. 5, an additional soldered connection can also be used instead of the additional adhesive connection, specifically using a solder with a melting point on the order of approximately 300 ° C. In any case, the melting point should be selected so that the properties of the reinforcing steel at the connection point are not changed during brazing.

The rebar connection shown in FIG. 5 can also be used for a wide variety of purposes in reinforced concrete construction. In principle, this connection or the reinforcing steels 101 and 102 or 102a used there can also be part of a connecting reinforcement or a reinforcement connection, as described above together with FIGS. 2 and 3.

FIG. 6 shows the preferred embodiment of the connection or the joint according to FIG. 1 again in an enlarged representation. As shown in Fig. 6, in the interior of the reinforcing steel 1 to the truncated cone-shaped recess 4 an essentially cylindrical portion 4 ', the remaining part of a hole that is in the reinforcing steel 1 for the manufacture of the section 4 with the Internal thread 5 was introduced. This section 4 'has a diameter db. In order to achieve optimal power transmission, it is necessary that the effective material cross-sectional area Fx, which the reinforcing steel 1 in the area of section 4 'has larger, but in any case equal to the cross-sectional area F2 of the reinforcing steel 2a determined by the diameter d. So the condition applies:
Fx greater / at least equal to F2
where Fx is the difference between the cross-sectional area F1 of the reinforcing steel 1 determined by the diameter D outside the recess 4 or section 4 'and the area FB determined by the diameter db, ie
Fx = F1 - FB.

Furthermore, the butt or thread length lg, ie the axial length over which the two threaded sections 5 and 6 of the connection mesh as a function of the angle a and also as a function of the diameters d and db, can be specified as follows :
lg = (d - db) / 2 tan a

In order to achieve optimum strength for the connection between the construction sites 1 and 2a on the one hand, but on the other hand to keep the butt length lg as short as possible and also to produce the frustoconical recess 4 with the internal thread 5 and the frustoconical section 6 with the external thread 7 as simply as possible shape, the angle a is preferably in the range between about 3 ° and 10 °, this angle a is preferably about 3 °. With this preferred angle a of 3 °, the connection is optimally strengthened and the thread or butt length lg is approximately 1.1 times to 4.7 times the diameter d. At an angle in the range between 4 ° and 5 °, the thread length lg is approximately 0.8 times to 3.6 times the diameter d. At an angle in the range between approximately 6 ° and 8 °, a joint length lg then results which is only approximately between 0.4 times and 2.4 times the diameter d. The above values are given for the usual diameters for reinforcing steel. In practice, the values are preferably somewhat higher, the joint length then corresponds to at least 1.25 to 1.5 times the diameter d.

As is known, the diameters of reinforcing steels are standardized and defined in a so-called reinforcing steel diameter series, which are determined by the following values (in mm):
- 6 - 8 - 10 - 12 - 14 - 16 - 20 - 25 - 28 - 32 -

In the preferred embodiment of the connection according to the invention, the reinforcing steels 1 and 2a are selected with regard to their diameters D and d in such a way that they or the Diameters D and d are adjacent in the aforementioned row of reinforcing steel. This pairing leads to a very significant improvement in the resilience of the connection. Since the maximum diameter of the truncated cone-shaped recess 4 is approximately equal to the diameter d of the reinforcing steel 2a, the effective cross-section of the reinforcing steel 1 in the region of the open end of the recess 4 in the case of the pairing of the reinforcing steel 1 and 2a or the diameter D and d relatively small and corresponds approximately to the difference between the cross-sectional areas F1 and F2 determined by the diameters D and d. Because of the small effective material cross section on the open side of the truncated cone-shaped recess 4, an increased elastic deformation of the material of the reinforcing steel 1 occurs in this area when the connection is loaded, and thus a substantial relief of the part of the thread of the connection adjacent to the open end of the recess 4 , with which a more even distribution of the power transmission over the entire thread or joint length lg is achieved. The conical shape of the recess 4 contributes decisively to an equalization of the power transmission within the screw connection, since the effective material cross section of the reinforcing steel 1 increases with increasing distance from the open end of the recess 4 and, accordingly, the elastic deformation of the material of the reinforcing steel 1 which relieves the thread decreases.

In the following tables, the optimum joint lengths lg are given for the angles a = 3 °, a = 4 °, a = 5 °, a = 6 °, a = 7 ° and a = 8 ° for different pairings of diameters D and d , but the actually used butt lengths can also be slightly larger to increase safety. Table I For a = 3 ° D (mm) d (mm) lg (mm) 8th 6 6.7 10th 8th 19.1 12 10th 32.4 14 12 45.8 16 14 60.1 20th 16 38.2 25th 20th 47.7 28 25th 118.3 For a = 4 ° D (mm) d (mm) lg (mm) 8th 6 5.0 10th 8th 14.3 12 10th 24.3 14 12 34.3 1 6 14 45.0 20th 16 28.6 25th 20th 35.8 28 25th 88.7 For a = 5 ° D (mm) d (mm) lg (mm) 8th 6 4.0 10th 8th 11.4 12 10th 19.4 14 12 April 27 16 14 36.0 20th 16 22.9 25th 20th 28.6 28 25th 70.9 For a = 6 ° D (mm) d (mm) lg (mm) 8th 6 3.3 10th 8th 9.5 12 10th 16.2 14 12 22.8 16 14 30.0 20th 16 19.0 25th 20th 23.8 28 25th 59.0 For a = 7 ° D (mm) d (mm) lg (mm) 8th 6 2.9 10th 8th 8.1 12 10th 13.8 14 12 19.5 16 14 25.7 20th 16 16.3 25th 20th 20.4 28 25th 50.5 For a = 8 ° D (mm) d (mm) lg (mm) 8th 6 2.5 10th 8th 7.1 12 10th 12.1 14 12 17.1 16 14 22.4 20th 16 14.2 25th 20th 17.8 28 25th 44.1

FIG. 7 shows a section or the profile of the internal thread 5 in a simplified, enlarged representation. The external thread 7 is designed accordingly. It is a fine thread with a pitch between 1 and 2 mm. The thread of the thread 5 is determined by the two flanks 5 'and 5˝, which include an angle b of about 90 ° with each other. This flank angle b ensures optimum power transmission and strength for the screw connection, in spite of the conical design of this screw connection and despite the fact that a reduction in the diameter of the reinforcing steel 2a also occurs in section 6 when the screw connection is subjected to tensile stress. The profile of the thread 5, but also of the thread 7 is arranged perpendicular to the longitudinal axis L, i. H. the bisector of the flank angle b lies approximately in a plane which is cut perpendicularly by the longitudinal axis L.

Regardless of the particular training, the connection according to the invention has significant advantages. It is thus possible, in particular, to provide the ribs which are customary in the case of reinforcing steels and which are necessary for incorporation in the concrete over the entire length of the interconnected reinforcing steels, specifically also in the region of the joint, as is indicated in FIG. 6 by the ribs 18. The bond between concrete and reinforcing steel is therefore not affected in the area of the connection between the joint.

Another significant advantage is that the connection according to the invention only requires a relatively short butt length, which is essentially determined by a thread length lg. This makes it possible to apply the invention even where only small lengths or thicknesses of concrete are available.

A very important advantage of the connection according to the invention is that no additional discontinuity with respect to the iron or Steel cross section occurs in a concrete component, as is the case for example with a socket connection, where the effective iron cross section changes at both transitions from the socket to the subsequent reinforcing steel. Such discontinuities in the iron or steel cross section lead to cracks in the concrete when the corresponding concrete structure is loaded.

As already mentioned above, the screw connection according to the invention can be used in a particularly advantageous manner as a reinforcement connection, but also to achieve an optimal adaptation of the reinforcement or reinforcement to the respective torque and / or load-bearing capacity profile in a concrete component.

In addition, other elements or measures can be optimally implemented with the invention. For example, by connecting a reinforcing steel 2a having the small diameter d to a length of the reinforcing steel 1 having the larger diameter D, the anchoring length of the reinforcing steel 2a necessary for anchoring in the concrete can be reduced. This is necessary, for example, if the anchoring length required for the required anchoring of the reinforcing steel 2a cannot be achieved due to the formation of a concrete component.

With the connection according to the invention, a bridging element or an element for length compensation can also be implemented in a particularly simple manner and without requiring a large amount of space or space, for example in order to connect two reinforcing steels which are arranged approximately axially with one another but are spaced apart from one another.

Claims (10)

1. Connection between at least two lengths of reinforcing steel, characterized in that the connection as a sleeve-less screw connection with a conical threaded bore (4) engaging in one length (1, 101) conical threaded section (6, 106) on the other length ( 2a; 102), and that the reinforcing steel forming the length (1, 101) has a diameter (D), at least in the area of the connection, which is greater than the diameter (d) of the other length (2a, 102) forming reinforcing steel. 2. Connection according to claim 1, characterized in that at least the one length (1, 101) forming reinforcing steel is a heat-treated steel. 3. Connection according to claim 1 or 2, characterized in that the inner surface of the conical threaded bore or the lateral surface of the conical threaded portion with the associated symmetry or longitudinal axis (L) an angle (a) approximately between 3 and 10 °, preferably one Includes angle (a) of about 3 °. 4. Connection according to one of claims 1-3, characterized in that the axial length (lg) of the thread is at least about 1.1 times the diameter (d) of the other length forming reinforcing steel, in the usual reinforcing steel diameters preferably about the 1st , 1 to 4.7 times this diameter (d). 5. Connection according to one of claims 1-3, characterized in that the axial length (lg) of the thread is at least about 1.25 times to 1.5 times the diameter (d) of the other length forming reinforcing steel. 6. Connection according to one of claims 1-5, characterized in that the two lengths (1, 2a) of the reinforcing steel have a reinforcement connection with an anchoring part to be anchored in a concrete component (9) to be created first and with a concrete component to be connected (10 ) form the connecting part to be anchored,
the one length (1) of the reinforcing steel with the larger diameter (D) preferably forming the anchoring part and the other length (2a) of the reinforcing steel with the smaller diameter (d) forming the connecting part,
and / or wherein the reinforcing steel (2a) forming the connecting part preferably has a greater length (X) than the reinforcing steel (1) forming the anchoring part. 7. Connection according to one of claims 1-6, characterized in that the threaded portion (6, 7; 106) directly to the other length (2, 2a; 102) of the reinforcing steel, for example. is applied by cutting, rolling or another shaping process. 8. Connection according to one of claims 1-7, characterized in that the sleeve-free screw connection is simultaneously designed as an adhesive or soldered connection. 9. Connection according to one of claims 1-8, that the interconnected reinforcing steels (1, 101; 2, 2a, 102) are in each case those with an adjacent diameter in a row of reinforcing bars. 10. Connection according to one of claims 1-9, characterized in that the thread of the connection is a fine thread and / or a thread with a leg angle of about 90 °.

Images