EP1231331A2 - Reinforcing bar with ribs and reinforced concrete - Google Patents

Abstract

Reinforcing steel comprises ribs (2) having a rib head width (b) greater than 0.2 times, preferably smaller than 0.5 times, especially 0.3-0.4 times, particularly 0.32-0.37 times the nominal diameter. Preferred Features: The angle ( beta ) of the rib to the longitudinal axis of the reinforcing steel is 25-55, preferably 35-45, especially 37-42 degrees , and is identical for all ribs. The reinforcing steel is rod-like and made by hot rolling.

Description

The present invention relates to a rebar with ribs. The present Invention is used wherever reinforcing steel is used to manufacture Reinforced concrete can be used. The present invention is particularly applicable to the production of reinforced concrete, especially here in the production of reinforcing steel mesh and reinforcing steel preferably used in rings.

In the case of reinforcement meshes, several reinforcing steel bars are laid crosswise on top of each other and welded at their points of contact. Usually for this Reinforcing steel cold-rolled reinforcing steel is used. Reinforcing steel is also common on coils, so-called "rings", wound up and transported on to the customer. For the further processing of this reinforcing steel, this is a straightening or bending and Cutting machine fed, or for example a mesh machine to reinforcing steel mesh manufacture. The reinforcing steel is used in so-called roller straightening sets or alternatively straightened in rotor straightening sets. For a rebar higher Quality is increasingly used in hot-rolled reinforcing steel. By the rib geometries prescribed in the corresponding reinforcing steel standards there are relatively pronounced ribs. The directional bars thus incline if, as is often the case, they are fed via a rod magazine for further processing become, when separating or pulling out of the magazine, to get caught. Furthermore, one obtains for cross welding for welding z. Partly unfavorably small contact areas. Because of the above Disadvantages with hot-rolled reinforcing steel has so far been used to manufacture Reinforcement meshes rarely used. For state-of-the-art reinforcing bars, For example, reinforcing steel according to DIN 488, the angle of inclination β is ribs on the surface are usually approx. 60 °. This geometrical arrangement the ribs affect the bond behavior of the reinforcing steel in the reinforced concrete.

The use of rebar without ribs is for most applications not possible because the ribs play an important role in the bond behavior play because the forces from the concrete are directed into the reinforcing steel via these ribs become.

1a to 1d show reinforcing steel according to the prior art, as in the DIN number 488 or in building inspectorate approvals. The reinforcing steel 1 has four rows of (in the Ribs 2 from top to bottom. The rib pitch angle β between the longitudinal direction of the rib under consideration and the direction of the Longitudinal axis A of the reinforcing steel in the case of reinforcing steel according to the prior art about 60 °. The distance between two ribs 2 in the longitudinal direction (rib spacing) is c, the rib head width of a rib 2 transverse to the longitudinal direction of the considered Rib is denoted by b. Is located between two adjacent ribs 2 a depression 8. FIG. 1d shows a section through the reinforcing steel 1 along the in FIG. 1b shown section line D.

2a in FIG. 1c is the rib head surface, 2b denotes the rib flank (on the other The side of the rib head surface 2a is also not visible in the drawing Rib flank present), and 8 is the dip between two neighboring ones Ribs 2. In FIG. 1d, 3 denotes the projection of a reinforcing steel in the longitudinal direction. The roughly circular contour is created by the backdrops one behind the other appearing and thus forming the circumferential contour ribs 2. The cutting contour 4 itself appears rather irregular. However, it occurs quite regularly in the manufacture of the reinforcing steel. Here, the roughly square Basic shape 5 with possibly rounded edges and the ribs 2 by rolling rolled into the raw material. This can be hot rolling or cold rolling. the Overall structure in cross-sectional area can thus be imagined as ribs 2, which sit on a base body with a square cross-section (reference number 5). The actual cross-sectional contour 4 results depending on where the Cross section cuts the respective ribs. What has just been said applies to reinforcing steel with four rows of ribs. The rows of ribs are through in the longitudinal direction of the material running webs 6 (rib row spacing or roll gap) and, depending on the Basic shape (e.g. round, square, hexagonal, etc.) and the rib milling depth, e.g. T. separated from each other by further webs 7 ..

The bond behavior of reinforcing steel in concrete is sketched in FIG. 2a. The association behavior specifies the force F with which the reinforcing steel must be pulled, so that there is a shift Δ1 of the reinforcing steel in the concrete. As a characteristic the bond tension is shown over the extension path. As shown in Fig. 2a is recognized, the bond stress reaches a maximum. With further postponement The strength of the reinforcing steel in the concrete decreases again because the bond of the Reinforcing steel weakened by shearing off the concrete base between the ribs becomes.

2b shows the expansion behavior of reinforcing steel. The reinforcing steel stretches in a first linear range, the elastic range, proportional to the applied force F up to a yield point F _S. The rebar then plastically deforms. This deformation is not reversible. Furthermore, a fatigue test is shown in which the reinforcing steel is subjected to a periodically changing force that is less than F _S. Although the applied force is so small that plastic deformation does not yet occur, such a load can lead to a fatigue fracture in the reinforcing steel.

These mechanical / dynamic properties (fatigue properties) are improvable. The static and dynamic forces introduced can then be caught safely and permanently.

An object of the present invention is to provide a reinforcing steel, which can be used in mat machines or automatic straightening and ironing machines, without problems during processing on the machine.

This object is achieved in that the rib inclination angle β to the longitudinal axis of the reinforcing steel 25 to 55 °, preferably 35 to 45 °, further is preferably 37 to 42 °. This small rib inclination angle β relative to Reinforcing steel axes have several advantages: Studies have shown that one such a low angle of inclination of the ribs significantly improves the fatigue properties can be achieved, i.e. a fatigue fracture of the reinforcing steel occurs less often or only after a longer time than with conventional reinforcing steel with a larger rib inclination angle. It occurs in the invention Reinforcing steel with a reduced rib inclination angle, less striking edges in the longitudinal direction of the reinforcing steel. This is what happens in reinforcing steel and in Concrete to lower stress spikes or notch stresses, which is common occur on such edges. The inclination results in the direction the longitudinal axis has a smaller slope than a rib with the same height, but a larger rib inclination angle. This can increase voltage or the notch effect of the reinforcing steel according to the invention is reduced become. Furthermore, the surface distribution is on the casing of the reinforcing steel in the direction of the longitudinal axis more evenly than with a ribbed reinforcing steel a steeper rib inclination angle.

In a preferred embodiment, the rib inclination angle is for all ribs of the reinforcing steel is essentially the same. So you can achieve the above Benefits over the entire length of the reinforcing steel.

The object is further achieved in that a rib head width b of the ribs is greater than 0.2 times, preferably less than 0.5 times of the nominal diameter, and more preferably 0.3 times to 0.4 times the Nominal diameter. This results in an improved rib filling in the rolling process, which leads to a lower ovality or uniform Roundness of the outer diameter of the reinforcing steel leads. This allows the reinforcing steel better processed. With the roundest possible reinforcing steels, i.e. With ovality as low as possible, the steel lies more evenly on the roller. Will the Rod, for example, between two opposite roles, that's it Play between the rollers with rods that are as round as possible does not depend on the position of the rod dependent. A rotation of the preferably rod-shaped reinforcing steel around your own Longitudinal axis does not change this game if the stick is round and not oval. In addition, the force parameters are then more even.

This also results in a more even surface distribution the envelope in the direction of the rod. This is for welding the reinforcing bars to reinforcing steel meshes advantageous because the welding surfaces of two superimposed Reinforcing steel bars are larger than conventional reinforcing bars with larger ones Rib slope angle and narrower rib.

The object of the present invention can also be achieved by that the ratio of the rib width in the longitudinal direction b 'to the rib spacing c in the direction of the reinforcing steel axis greater than 0.35, preferably greater than 0.4 is preferably greater than 0.45. This also leads to a more even distribution on the enveloping in the direction of the rod, which has the advantages mentioned above. This ratio of the rib width in the longitudinal direction to the rib spacing is suitable also when used in high-strength concrete or for an application in self-compacting concrete (SVB, slump according to ASTM at least 60 cm, preferably at least 65 cm, more preferably at least 70 cm).

The reinforcing steel is preferably produced by hot rolling.

Furthermore, the preferably rod-shaped, but often also supplied as a coil Reinforcing steel have several rows of ribs, preferably 4. However, it can 2, 3 or 6 rows of ribs can also be provided.

The degree of rib coverage is preferably greater than 45%, more preferably greater than 50%, more preferably greater than 55%.

The minimum value of the related rib surface is preferably in the range between 30% below and 30% above the minimum value prescribed in DIN 488 .. This applies above all to reinforcing bars with a nominal diameter of greater than or equal to 4 mm.

The invention further relates to a reinforced concrete with a reinforcing steel, which is designed as described above, wherein concrete with a compressive strength is used which is greater than 55 N / mm ² , preferably greater than 65 N / mm ² , ie high-strength concrete. The present invention also relates to the use of reinforcing steel, wherein the reinforcing steel is preferably used for the production of reinforced concrete with high-strength concrete with a strength of 55 N / mm ² or greater, preferably 65 N / mm ² and greater. The present invention is of course not limited to high strength concrete, it can also be used with self-compacting or other concrete.

Fig. 1a bis 1d

eine Seitenansicht, eine um die Längsachse um 90° gedrehte Seitenansicht, eine perspektivische Ansicht sowie einen Schnitt an der Linie D von Fig. 1b eines Betonstahls nach dem Stand der Technik,

Fig. 2a

schematisch das Verbundverhalten von Betonstahl in Beton und Fig. 2b eine Dehnungskurve für Betonstahl,

Fig. 3a und 3b

zwei um 90° um die Längsachse gedrehte Ansichten eines erfindungsgemäßen Betonstahls, und

Fig. 4

eine Skizze zur Ermittlung des Rippenbedeckungsgrades.

The invention is explained below with reference to the accompanying schematic drawings using an exemplary embodiment. Here show:

1a to 1d

2 shows a side view, a side view rotated by 90 ° about the longitudinal axis, a perspective view and a section along line D of FIG. 1b of a reinforcing steel according to the prior art,

Fig. 2a

schematically the bond behavior of reinforcing steel in concrete and Fig. 2b an elongation curve for reinforcing steel,

3a and 3b

two views rotated by 90 ° about the longitudinal axis of a reinforcing steel according to the invention, and

Fig. 4

a sketch to determine the degree of rib coverage.

In the figures, the same reference symbols generally mean the same components or characteristics.

3 shows a reinforcing steel according to the invention. The rib pitch angle β is between 25 ° and 55 ° and preferably about 40 ° +/- 5%. The rib head width b is greater than 0.2 times and preferably less than 0.5 times of the diameter. The diameter can be the nominal diameter (i.e. the Diameter of an equally heavy rod with a circular cross-section). It can but also about the maximum diameter (corresponding to contour 3 in Fig. 1d) act or the diameter that results from the valleys 2c. The characteristic with regard to the rib inclination angle β can be independent of or together can be realized with the features mentioned below. Also the characteristics mentioned below with regard to rib head width b, the rib width b 'in the longitudinal direction, the related rib area and the degree of rib coverage can be viewed on their own as the subject of the invention.

The rib head width b is larger than in the case of reinforcing steel according to the prior art. The ratio of the rib width in the longitudinal direction b 'to the rib spacing c is larger than 0.35, which is not the case with state of the art reinforcing steel. There is this ratio is less than 0.35. In the illustrated embodiment, the invention is Reinforcing steel shown with four rows of ribs. However, it can just as well a different number of rows of ribs can be used. The rows of ribs preferably extend in the longitudinal direction of the reinforcing steel. In Fig. 3b there are two indicated by the reference numerals 9 and 10. The rows of ribs are each limited by webs 6 and 7 if necessary.

The connection of the larger rib width in the longitudinal direction b 'and the smaller one Rib inclination angle β leads to better rib filling, especially in combination and therefore less ovality. This results in one if possible large area on the envelope, evenly distributed in the longitudinal direction. These geometric properties improve the processing options on the processing machines, jamming of the reinforcing bars in the machine is prevented. There is also a larger welding area available which improves the connection between two welded reinforcing bars.

wobei

die Längsschnittfläche einer Rippe in deren Achse

h_S

die mittlere Höhe eines beliebigen Schrärippenabschnitts der Länge Δl der in x Abschnitte unterteilten Schrägrippe

β

die Neigung der Rippen zur Stabachse hin

d_S

der Nenndurchmesser des Stabes in mm

c_S

der Mittenabstand der Schrärippen in mm

k

die Anzahl der Schrägrippen am Umfang

m

die Anzahl der Schrägrippen je Reihe

i

die Anzahl der Längsrippen

h_l

die Höhe der Längsrippen

(n), (n, l)

Laufvariablen sind.

The related rib area f _{R is} calculated using the formula

in which

the longitudinal sectional area of a rib in its axis

h _p

is the average height of any section of wedge rib of length Δl of the wedge rib divided into x sections

β

the inclination of the ribs towards the bar axis

d _p

the nominal diameter of the rod in mm

c _p

the center distance of the wedge ribs in mm

k

the number of diagonal ribs on the circumference

m

the number of helical ribs per row

i

the number of longitudinal ribs

h _l

the height of the longitudinal ribs

(n), (n, l )

Are run variables.

It is a measure of how much fin cross-sectional area there is on the reinforcing steel, relatively speaking. A priori, a high covered rib area is desired, since then a good bond between reinforcing steel and the surrounding concrete can be expected. Under certain conditions and especially in connection with high-strength concretes (strength greater than 55 N / mm ² ), a comparatively small covered rib surface can deliver the same or even better results. According to the invention, reinforcing steels with a related fin area f _{R of} less than 130% of the minimum value provided in DIN 488 appear to be advantageous. The related rib area is preferably less than 115%, more preferably less than 100%.

The improved geometry results in the processing of the reinforced concrete less noise, especially in roller straightening systems and roller guides and less impact on mechanical, dynamic and geometric Properties due to the processing machines used. This means, that the processing of preferably hot-rolled steel significantly is improved.

Reinforced concrete can be produced with a reinforcing steel as described above. The reinforced concrete then has a concrete and the reinforcing steel described above. The concrete preferably has a strength which is greater than 55 N / mm ² .

The use of the reinforcing steel described above for the production of reinforced concrete is also an aspect of the invention. The concrete used preferably has a strength of at least 55 N / mm ² , more preferably at least 65 N / mm ² . The stated strength is a compressive strength.

Fig. 4 shows a sketch for determining the degree of rib coverage, where c is the Rib spacing, b is the rib head width and l 'the rib length. The degree of rib coverage is - clearly speaking - the proportion of the hatched area A on the envelope in relation to the total envelope of the reinforcing steel, where the areas of webs 6 and 7, if applicable, are included.

b = Rippenkopfbreite,

l' = Länge der Rippen in Rippenrichtung innerhalb einer Schrittweite c,

e = Stegbreite (Rippenreihenabstand),

c = Rippenabstand in Längsrichtung,

d = Nenndurchmeser.

The degree of fin coverage is a relative measure of the area occupied by fin heads 2a and webs 6, 7 on the envelope of a reinforcing steel. The rib coverage ratio RBG is preferably calculated using the following formula: RBG = b · Σ l '+ c Σ e d · Π · c · 100%. With

b = rib head width,

l '= length of the ribs in the rib direction within a step width c,

e = web width (rib row spacing),

c = rib spacing in the longitudinal direction,

d = nominal diameter.

The summation takes place over the scope.

The required degree of rib coverage has the advantage that the smoothness and improve the directionality of the reinforced concrete. Likewise, the risk of snagging is processing less, and the weldability is due to the larger contact areas better.

Typical diameter of rod-shaped material of the reinforcing steel is a minimum of 4 mm, maximum 65 mm, preferably minimum 6 mm, maximum 32 mm. Typical lengths rod-shaped material is a minimum of 2 m, a maximum of 30 m, preferably minimal 6m, maximum 24m. Typical diameters of rebar rings are minimal 0.5 m, maximum 2 m, preferably minimum 0.7 m, maximum 1.8 m. The reinforcing steel can also be mat-shaped. Then here are bars that are like above are formed, connected to one another in a lattice shape, preferably welded. The reinforcing steel can also be used as prefabricated or built-in reinforcement, e.g. B. as Lattice girder, reinforcement cage or reinforcement bracket or rod designed in a fixed length his.

In summary, the new geometry, i.e. the wider rib and the lower rib inclination angle of a hot-rolled reinforcing steel that can be processed well. Likewise, the reinforcing steel according to the invention are naturally cold rolled.

Claims (11)

Reinforcing steel (1), in particular according to claim 1 or 2, with ribs (2), characterized in that a rib head width b of the ribs (2) is greater than 0.2 times, preferably less than 0.5 times, more preferably that 0.3 to 0.4 times, more preferably 0.32 to 0.37 times the nominal diameter. Reinforcing steel (1) with ribs (2), characterized in that the rib inclination angle β to the longitudinal axis of the reinforcing steel is 25 ° to 55 °, preferably 35 ° to 45 °, further preferably 37 ° to 42 °. Reinforcing steel (1) according to claim 1, characterized in that the rib inclination angle is essentially the same for all ribs (2). Reinforcing steel (1), in particular according to one of the preceding claims, with ribs (2), characterized in that the ratio of the rib width in the longitudinal direction b 'to the rib spacing c in the direction of the reinforcing steel axis (A) is greater than 0.35, preferably greater than 0, 40, more preferably greater than 0.45. Reinforcing steel (1) according to one of the preceding claims, characterized in that the reinforcing steel is rod-shaped. Reinforcing steel (1) according to one of the preceding claims, characterized in that the reinforcing steel is produced by hot rolling. Reinforcing steel (1) according to one of the preceding claims, characterized in that it has several rows of ribs, preferably four. Reinforcing steel (1) according to one of the preceding claims, characterized in that the degree of rib coverage is greater than 45%, preferably greater than 50%, further preferably greater than 55%. Reinforcing steel (1) according to one of the preceding claims, characterized in that the related rib surface f _{R is} less than 130% of the minimum value prescribed in DIN 488, preferably less than 115%, more preferably less than 100%. Reinforced concrete (1) with a reinforcing steel according to one of the preceding claims and a concrete, preferably a strength which is greater than 55 N / mm ² , more preferably greater than 65 N / mm ² . Use of reinforcing steel according to one of claims 1 to 9, characterized in that the reinforcing steel is used for the production of reinforced concrete with concrete with a strength of preferably greater than 55 N / mm ² , more preferably greater than 65 N / mm ² .

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