EP0307680B1 - Concrete reinforcing rod, particularly a concrete ribbed bar - Google Patents

Abstract

In order to make a concrete reinforcing rod (1), exhibiting a characteristic ribbed arrangement for identification of the steel quality or origin, suitable for a threaded connection, mutually parallel oblique ribs (2, 3) are arranged on both circumferential halves along a helix and ribs (4, 5) lying outside this helix are reduced in height to such an extent that they do not hinder the screwing-on of the associated anchoring or connecting member. <IMAGE>

Description

The invention relates to a reinforcing steel bar according to the preamble of claim 1.

In addition to the task of ensuring a sufficient bond in the concrete - a measure of the bond is the so-called related rib area - the ribs of a concrete reinforcement bar are also assigned the task of identifying the product with regard to the steel grade and origin.

For example, the Euronorm 80-85 stipulates that two rows of parallel oblique ribs, which are opposite each other, must be provided for the identification of the steel grade Fe B 400, whereby the oblique ribs on the two circumferential halves must have different distances. The steel grade Fe B 500 is characterized by two rows of inclined ribs, one of which has parallel inclined ribs and the other row of alternating inclined ribs to the bar axis. The country of origin and the manufacturing plant are identified by a certain number of normal diagonal ribs between widened diagonal ribs. The concrete reinforcement bar is thus identified by means of different characteristic rib arrangements.

A concrete reinforcement bar according to the preamble of claim 1 has become known from DE-A-2622524. To reduce the explosive effect and achieve a low notch sensitivity, a number of lower oblique ribs are arranged in the known concrete reinforcement bar between two high oblique ribs in such a way that the related rib surfaces of the lower and the high ribs are in a certain relationship to one another. To unscrew it to prevent the rod from the concrete, have successive inclined ribs of different inclination in the longitudinal direction of the rod, or at least one longitudinal rib is provided in addition to the inclined ribs. The choice of inclined rib inclinations is determined by the aspects of composite effect, rolling technology and bar marking. In one embodiment, lower ribs are arranged along a two-start thread.

From DE-Z concrete and reinforced concrete construction 2/1973, pages 25 to 35, screwable concrete reinforcement bars, known as GEWI steel, have become known, in which the ribs are arranged along at least one helical line and parts of a single or multi-start thread for screwing on a form with an appropriate counter thread anchoring or connecting body. To at one Given the predetermined load, the threaded connection, that is, to be able to keep the anchoring or connecting body as short as possible, the aim is for the longitudinal section of the reinforcing bar to have a regular smooth undulating course in an axial plane in the region of the ribs (DE-OS 3517638). The clear distance between the ribs then corresponds approximately to the rib width.

The object of the invention is to arrange and design the ribs in a ribbed steel according to the preamble of claim 1, in which the rib arrangement and rib shape serves to identify the type of steel and / or the origin, in such a way that anchoring or anchoring at any interfaces of this concrete reinforcement bar Connection body can be screwed on.

This object is achieved by the features of patent claim 1. Advantageous embodiments of the invention can be found in the remaining claims.

In the concrete reinforcement bar according to the invention, ribs which have a position lying outside the helical line of a single-threaded thread or the helical lines of a two-thread or multi-threaded thread or are widened have a rib height which is reduced to such an extent that they unscrew the associated anchoring or connecting body is not hindered. However, these ribs cannot participate in the load-bearing function of the threaded connection, so that the length of the anchoring or connecting body must be increased for the same mechanical stress.

This can be avoided by correspondingly increasing the shear strength of the concrete reinforcement bar in the area of the ribs, so that the ribs are responsible for the power transmission can be used to transmit a higher force. In view of the dynamic load-bearing capacity of the threaded connection, in addition to the shape and arrangement of the ribs described, a reinforcing steel is preferably used which has increased strength in the edge and rib area compared to the core, for example a reinforcing steel as described under the trade name Tempcore- Steel (registered as a trademark) has become known. Such steels are produced in such a way that they are so intensely cooled by a water cooling section when they emerge from the last rolling stand of a hot rolling mill in the edge zone that there is a hardness structure in this zone and the hardened edge zone after the rod emerges from the water cooling section due to the heat content the core zone is started. They not only have increased strength compared to the core, but also a higher coefficient of friction on their surface and thus in the rib area compared to other hot-rolled concrete reinforcement bars. An increased coefficient of friction is desirable with regard to the self-locking of the threaded connection.

Fig. 1

einen Abschnitt eines schraubbaren Betonbewehrungsstabes mit einer für die Stahlsorte Fe B 400 charakteristischen Rippenanordnung,

Fig. 2

einen Abschnitt eines schraubbaren Betonbewehrungsstabes mit einer für die Stahlsorte Fe B 500 charakteristischen Rippenanordnung.

The invention is explained by two exemplary embodiments with reference to two figures. Show it:

Fig. 1

a section of a screwable concrete reinforcement bar with a rib arrangement characteristic of the steel grade Fe B 400,

Fig. 2

a section of a screwable concrete reinforcement bar with a rib arrangement characteristic of the steel grade Fe B 500.

The concrete reinforcement bar 1 shown in FIG. 1 has a circular core cross section and two mutually opposite rows of ribs 2 and 3. These ribs are arranged along a first helix of a single-start thread. Between the ribs 2 are additional ribs 4, which are arranged along a second helix offset by 180 ° with respect to the first helix, so that a rib arrangement corresponding to a two-start thread is realized on the bar half shown in FIG. 1 above, while the rib arrangement on the lower half of the rod only corresponds to a single thread. In the case shown, the additional ribs 4 have a rib height that is so far reduced compared to the ribs 2 or 3 that the screwing on of an associated catchy anchoring or connecting body is not hindered by them. No forces can thus be entered into the anchoring or connecting body via these additional ribs 4. In the case of the rib arrangement shown in FIG. 1, however, this is possible if the ribs 4 are formed at the same height as the ribs 2 and the associated anchoring or connecting body has a two-start internal thread.

On the lower half of the bar, individual ribs 5 widened relative to the ribs 3 or 2 are provided. These must have a rib height that is so far reduced compared to the ribs 3 or 2 that the screwing on of the associated anchoring or connecting body is not hindered by them.

Even if the additional ribs 4 are designed as supporting ribs of a two-start threaded connection, because of the lack of additional ribs on the lower half of the rod and because of the widened ribs 5, the load capacity is reduced compared to a conventional two-start threaded connection of the same pitch. If equally large forces are to be transmitted, the length of the anchoring or connecting body would have to be increased. That can can be counteracted by increasing the strength in the area critical for the loading of the threaded connection, that is to say in the edge and rib area of the concrete reinforcement bar. A steel is preferably used in which a quenching and tempering treatment from the rolling heat results in an increased strength in the edge and rib area of the concrete reinforcement bar compared to the core.

2, the arrangement of the ribs 2 and 3 corresponds to that of the ribs with the same numbering in the first exemplary embodiment according to FIG. 1. However, the additional ribs 4 are not arranged here along a helix offset by 180 ° to form a two-start thread, but have a different inclination than the ribs 2. The top half of the bar of FIG. 2 has a row of ribs made of inclined ribs 2 and 4 alternately inclined to the bar axis in plan view. Thus, the additional ribs 4 must have a rib height which is so far reduced compared to the ribs 2 that the screwing on of the associated anchoring or connecting body is not hindered by them. The diameter D shown in FIG. 2 of the cylindrical envelope of the additional ribs 4 must be smaller than the inside diameter of the thread of the anchoring or connecting body to be screwed onto the concrete reinforcing bar.

It is also advantageous with this rod if the strength in the edge and rib area of the concrete reinforcement rod is increased, since here the ribs 2 and 3 that can be used for the threaded connection must be relatively narrow due to the space required for the additional ribs 4, or the pitch of the helix , along which these ribs are arranged, must be relatively steep. But this also applies to the load-bearing behavior of the threaded connection decisive shear area per unit length is relatively small.

The bond is increased in both exemplary embodiments by the additional ribs 4 or projections formed in another way. If the additional ribs 4 have a significantly lower height than the ribs 2 or 3, a particularly soft bond is achieved. If necessary, additional ribs 4 of correspondingly low height can be provided between the ribs 2 or 3. Likewise, incisions or impressions 6 can also be provided in the concrete reinforcement bar in order to improve the composite effect of the bar in the concrete and at the same time to have other identification means available.

With regard to a sufficient covered rib surface, it is advantageous if the ribs each extend almost over half the rod circumference at full height.

Claims (9)

1. A concrete reinforcing bar (1), in particular a ribbed concrete reinforcing bar, of circular or almost circular core cross-section and with two mutually opposite rows of ribs (2, 3, 4, 5) which, for identification of the type of steel and/or the origin have a characteristic rib arrangement and/or individual widened ribs (5), in which moreover mutually parallel inclined ribs (2, 3) are arranged on both peripheral halves along at least one helical line, characterised in that the inclined ribs form portions of a single-flight or two-flight thread for screwing on an anchoring or connecting body provided with a corresponding co-operating thread and ribs (4 or 5) which are in a position lying outside the respective helical line or are widened are of a rib height which is reduced to such an extent that screwing on of the associated anchoring or connecting body is not obstructed thereby.

2. A concrete reinforcing bar according to claim 1 characterised in that the ribs (2, 4) of the one row of ribs are arranged along two helical lines of a two-flight thread, which are displaced by 180° with respect to each other, and the ribs (3) of the opposite other row of ribs are arranged only along one of the two helical lines.

3. A concrete reinforcing bar according to claim 1 characterised in that the ribs (2, 3) of both rows of ribs are arranged along a helical line and a row of inclined ribs (2, 4) which are inclined alternately to the axis of the bar is formed by the arrangement of mutually parallel additional ribs (4) of reduced rib height and with a different inclination.

4. A concrete reinforcing bar according to one of claims 1 to 3 characterised in that incisions or impressions (6) are provided between the ribs of at least one row of ribs.

5. A concrete reinforcing bar according to one of claims 1 to 4 characterised in that the ribs (2, 3, 4, 5) each extend at their full height over almost half the bar periphery.

6. A concrete reinforcing bar according one of claims 1 to 5 characterised in that in the edge and rib region it is of increased strength with respect to the core.

7. A concrete reinforcing bar according to one of claims 1 to 6 characterised in that the ribs (2, 3) which can be used for the thread connection are of a rib shape which is trapezoidal in cross-section and which with the following definitions:
b = base width of the rib
d_s = nominal diameter of the concrete reinforcing steel member
h = rib height
β = angle of inclination of the rib flank in degrees of angle satisfies the following conditions:
$$\text{40° < β < 60°}$$

$${\text{0.04 ≦ h/d}}_{\text{s}}\text{ ≦ 0.06}$$

$$\text{1.5 ≦ b/h ≦ 3.3}$$

8. A concrete reinforcing bar according to claim 7 characterised in that 2.0 ≦ b/h ≦ 3.0.

9. A method of making a concrete reinforcing bar according to one of claims 1 to 8 characterised in that after leaving the last roll stand of a hot rolling installation it is intensively cooled in the edge zone by a water cooling line in such a way that in that zone martensite and/or bainite formation occurs and after the bar issues from the water cooling line the hardened edge zone is tempered by the heat content of the core zone.

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