EP2000609A1 - Reinforcing bar - Google Patents

Abstract

A reinforcing rod has ribs superimposed on each other along with a cylindrical base shape with a circular cross-section, starting from which first (2) and second (3) recesses extend radially inwards and form first (4) and second (5) ribs that overlap each other. The recesses run in directions opposite to each other, i.e. one recess runs to the right and the other recess runs to the left along the reinforcing rod in the form of a screw thread around the rod. The first recesses are made deeper than the second recesses.

Description

The invention relates to a reinforcing rod made of fiber-reinforced plastic, provided on its peripheral surface with a radially outwardly projecting profiling in the form of at least over part of the circumference extending ribs.

From the DE-A-101 21 021 is such a reinforcing rod made of fiber-reinforced plastic known, which starts from the task of entering into a strong bond with the plastic reinforcing rod surrounding concrete. In particular, two types of failure come into consideration, which must be avoided: First, the shearing of the ribs in consequence to high axial tensile loads and insufficient transfer of effective forces from the concrete in the reinforcing bar and vice versa; on the other hand the danger of the so-called splitting tensile failure with flat ribs, by which the concrete surrounding the ribbed reinforcing bar is exposed to an ever-increasing bar circumference under tensile loads and finally burst open. In the DE-A-101 21 021 Accordingly, it is proposed that the lateral rib flanks of the ribs of the reinforcing bar should be inclined at an angle of more than 45 ° with respect to the bar axis and that the axial width of the ribs should be greater than the distance between two adjacent ribs.

This should ensure that the concrete is prevented from bursting open by angles of the rib flanks which are too shallow and, above all, that the ribs have a sufficient bond with the rest of the reinforcing bar.

This second aspect of the improved composite is attempted in other known rebars in that the rod surface is provided with a sanding, helical constrictions (s.p. EP-A-0 199 348 ) or Tordierungen (or constrictions). However, a common measure consists in cutting trapezoidal threads through which also ribs arise - or rather a single helical continuous rib - in the left between the wells of adjacent threads bar area.

Accordingly, the following is also referred to as ribs if they do not protrude radially, starting from an inner lateral surface with a smaller diameter to the outside, but also if - as in the case of the incised thread - consist of a part of the rod lateral surface and through this lateral surface introduced recesses are formed.

In a known embodiment, a thread geometry is defined in which the concrete brackets, ie the concrete located adjacent to the bar in the area between two adjacent ribs, fail up to a certain concrete strength between the ribs. A disadvantage of this thread form is that at a higher concrete strength, the ribs shear off completely and thereby the residual composite stress drops drastically. As concrete hardens more and more with increasing aging, this can lead to an abrupt failure of the reinforcement even after a long undamaged time when a threshold value is exceeded.

Usually in concrete constructions attempts are made to limit the crack width, which has not only optical, but also mechanical reasons. Since reinforcing bars made of fiber-reinforced plastic (so-called GRP reinforcing bars) have a lower modulus of elasticity than steel and thus wider cracks in GRP-reinforced concrete structures are to be expected compared to reinforced concrete structures With the same reinforcement content, steel reinforcement rods are currently also generally used.

On this basis, the present invention seeks to provide a reinforcing rod made of fiber-reinforced plastic of the type mentioned above, which is characterized by improved properties and is particularly suitable for receiving higher loads. Accordingly, a reinforcing rod made of fiber-reinforced plastic is to be made available in particular, which avoids the disadvantage of conventional GRP reinforcing rods and, for example, helps to reduce the crack spacing and the crack width in the concrete surrounding the reinforcing rod. In this case, instead of some large gaping cracks in the concrete, it is expedient to produce a plurality of smaller cracks, which then, in addition to a better visual impression, also result in improved ductility of the concrete component.

This object is achieved in that the reinforcing rod has ribs with different geometric and / or material properties. In this way, an order system of different rib properties can be formed, in which the ribs of different order with respect to the geometric parameters such as rib width, rib spacing, rib depth, angle of the rib flanks, rib division etc. or by varying the glass fiber content, the fiber materials, the fiber orientations, etc. differ and their Properties can complement.

Advantageous developments of the reinforcing bar according to the invention are each the subject of dependent claims, the wording of which is incorporated by reference into the description in order to avoid unnecessary text repetitions.

Advantageously, the ribs with different geometric and / or material properties are formed so that they have a different shear stress on the ribbed bottom. As a result, the said order system of different rib properties advantageously leads to a distinction with regard to the respective rib loads.

The properties of higher order ribs are desirably chosen such that the shear stress at the rib bottom of the higher order rib is greater than the shear stress at the rib bottom of the lower order rib.

Above all, it should be ensured that the ribs with different geometrical and / or material properties are designed so that they do not fail in the load case time and / or load same, as for example in the known reinforcing bars of the prior art (see, for example WO 95/13414 ) with two helically opposed intersecting ribs which are arranged symmetrically in the axial direction, which means a symmetrical shearing stress and thus, as a rule, a simultaneous failure. If failure can be prevented at the same time and / or under the same load, this increases the ductility of the reinforcing bar.

In order for the ribs having different rib geometries and / or fin materials to support each other in the inventive manner, they should be disposed at least approximately in the same axial portion of the reinforcing bar - either axially adjacent to one another or spaced apart or overlapping one another or overlaid.

Thus, for example, there is a particular advantage in that it is possible to combine wide ribs of the first order with narrower ribs of the second or higher order in such a way that the narrower ribs are arranged on the wider ribs on their radial outer side. As a result, it can be achieved that, in the event of loading, the narrower second-order ribs initially shear off when the stress at the rib bottom of these narrower ribs exceeds their shear strength.

By shearing these narrower ribs, the contact surface of the reinforcing bar is reduced in the area of the remaining wider first-order rib with the concrete bar surrounding the reinforcing bar and thus initially reducing the stress on the ribbed bottom of this wider first-order rib. Thus, the remaining first-order rib can again absorb additional loads until the shear stresses also exceed the shear strength at the ribbed bottom of the first-order ribs and lead to their shearing off.

With the help of the different rib properties, one obtains an "onion peel effect", as it were: certain strains initially lead to damage of the "outer onion skin", i. the narrower or outer ribs of higher order. These sheared ribs no longer contribute to the reinforcing bar being able to absorb tensile stresses on the concrete, but instead lie loosely between the reinforcing bar and the concrete, absorbing the stresses from the remaining (lower order) ribs. If the loads increase, this leads to failure of the ribs of the next lower order when the associated threshold value is exceeded. Finally, in spite of damaged, still present, loose "outer onion skins", i. Higher order ribs nor the composite of the concrete with the "innermost onion skin", i. the ribs of the first order.

In this "onion peel" effect, it is particularly important that, despite any sheared off ribs of higher order, the residual load capacity of the lower order fin (s) has a defined value, which then provides the further load capacity of the associated reinforcing bar.

The ribs of different order can be arranged not only synchronously, for example rotationally symmetric, helical or counter-uniformly distributed over the reinforcing rod, but they can also follow different arrangement patterns, for example, with opposite different slopes to a point-like distribution of the ribs highest order, for example Sanding (in the case of positive ribs) or sandblasting (in the case of negative ribs) can be formed, which has the advantage of a higher bond activation with small slip paths. However, this should be based on defined properties in the sanded or sandblasted areas to prevent undefined randomness and thus negative effects in the stressed state.

As a result of the classification system according to the invention of different rib properties, in contrast to the bars of the prior art, when certain load threshold values are exceeded, there is no sudden shearing of all ribs and failure of the entire reinforcement provided by the reinforcing bar; rather, at first only the least resilient ribs of the highest order are scrapped. This reduces the remaining contact surface of the reinforcing bar with the concrete brackets, increases the slip between the bar and concrete and according to the invention leads to very advantageous load reserves.

Only when the load increases - for example, when the concrete strength increases over time - shears the ribs of the next lower order occurs when the corresponding threshold is exceeded.

It should be noted that in the prior art steel reinforcing bars there are already designs which aim at a "graded failure mode" with the aim of avoiding excessive deformation of the steel and keeping its ductility high. It should then not - as with the present plastic reinforcing bars - fail the rod material in the ribs, but the concrete surrounding the bar in the area of a single concrete console, before then fails in a next stage of concrete in the area of a larger concrete console. While it is a primary goal in the present invention to provide a defined residual capacity, in this prior art graded failure mode seeks and enables greater relative displacements of the steel rod from the reinforced concrete component thus reinforced, so that the reinforced concrete component also extends below Utilization of local plastic deformation of the reinforcement can be measured.

Furthermore, a rib geometry can thus be provided for a high-load rib, which can also be used for concrete with the highest strength and does not lead to rib failure of the reinforcement, but rather if necessary, a failure of the concrete console between the ribs. While low strength ribs provide a good bond in normal concrete, the high rigidity ribs provide a minimum composite strength, even for highly cured concrete or concrete with overstrength.

Finally, ribs of different order can be combined in a multi-step rib, which may have discrete angular jumps or continuous angle changes. In this case, different rib properties are combined with each other, whereby in turn the ribs of higher order have a lower shear strength and fail earlier than the ribs of lower order. This can prevent that at a certain time, the whole rib shears off; instead, one of the fractal sub-ribs initially shears because the tension in the rib bottom of this sub-rib exceeds the shear strength. As a result, the contact surface of the remaining sub-ribs with the surrounding concrete, the so-called. Concrete console is reduced and thus reduces the stress on the ribbed bottom of these remaining sub-ribs. Thus, these remaining sub-ribs can take up additional loads until the shear stress on the rib bottom of the then smallest sub-rib is exceeded and leads to their shearing.

For the production of such a reinforcing rod according to the invention, in addition to the conventional methods (such as shaping of the ribs during the pultrusion process), it is also advisable to mill the rib geometry into the hardened reinforcing rods, whereby a very wide variety of geometrical properties can be achieved without much effort. In this case, the base profile of the reinforcing rod may also have a non-circular or oval, quadrangular, star-shaped etc. cross section. Likewise, the milling process can be circular or oval, centric or eccentric. By combining the basic profile of the reinforcing bar and the milling process, different geometric properties can be achieved with the simplest means and thus represent different rib strengths.

Figur 1

eine erste Ausführungsform eines erfindungsgemäßen Bewehrungsstabs

• in Seitenansicht - in Figur 1 a),
• im Vertikalschnitt - in Figur 1 b),
• im Horizontalschnitt entlang A-A aus Figur 1a) - in Figur 1c),
• im Horizontalschnitt entlang B-B aus Figur 1a) - in Figur 1d), das Detail A aus Figur 1 b) - in Figur 1 e),
• das Detail B aus Figur 1b) - in Figur 1f) und
• in perspektivischer Seitenansicht - in Figur 1 g);

Figur 2

eine zweite Ausführungsform eines erfindungsgemäßen Bewehrungsstabs in Seitenansicht - in Figur 2a) - und in perspektivischer Seitenansicht - in Figur 2b);

Figur 3

eine dritte Ausführungsform eines erfindungsgemäßen Bewehrungsstabs in Seitenansicht - in Figur 3a) - und in perspektivischer Seitenansicht - in Figur 3b);

Figur 4

auszugsweise einen Vertikalschnitt durch eine vierte Ausführungsform eines erfindungsgemäßen Bewehrungsstabs;

Figur 5

auszugsweise einen Vertikalschnitt durch eine fünfte Ausführungsform eines erfindungsgemäßen Bewehrungsstabs;

Figur 6

auszugsweise einen Vertikalschnitt durch eine sechste Ausführungsform eines erfindungsgemäßen Bewehrungsstabs; und

Figur 7

auszugsweise einen Vertikalschnitt durch eine siebte Ausführungsform eines erfindungsgemäßen Bewehrungsstabs.

Further features and advantages of the present invention will become apparent from the following description of various embodiments with reference to the drawing; show here

FIG. 1

a first embodiment of a reinforcing rod according to the invention

• in side view - in FIG. 1 a) .
• in vertical section - in FIG. 1 b) .
• in horizontal section along AA FIG. 1a ) - in Figure 1c )
• in horizontal section along BB FIG. 1a ) - in Figure 1d ), the detail A off FIG. 1 b) - in FIG. 1 e) .
• the detail B off FIG. 1b ) - in FIG. 1f ) and
• in perspective side view - in FIG. 1 g) ;

FIG. 2

a second embodiment of a reinforcing rod according to the invention in side view - in FIG. 2a ) - and in perspective side view - in FIG. 2b );

FIG. 3

a third embodiment of a reinforcing rod according to the invention in side view - in FIG. 3a ) - and in perspective side view - in FIG. 3b );

FIG. 4

extracts a vertical section through a fourth embodiment of a reinforcing bar according to the invention;

FIG. 5

excerpts a vertical section through a fifth embodiment of a reinforcing rod according to the invention;

FIG. 6

excerpts a vertical section through a sixth embodiment of a reinforcing rod according to the invention; and

FIG. 7

excerpts a vertical section through a seventh embodiment of a reinforcing rod according to the invention.

In the FIGS. 1a) and 1b ) is a reinforcing rod 1 can be seen with two superimposed ribs. In this case, the reinforcing rod 1 consists of a cylindrical basic shape with a circular cross-section, starting from which first recesses 2 and second recesses 3 extend radially inward, whereby they form overlapping ribs 4, 5. The recesses 2, 3 are arranged in opposite directions, that is, the one recess runs on the right-hand side and the other recess extends left-handed along the reinforcing rod helically around it. The recesses 2 are formed deeper than the wells 3. The wells 2 leave between each ribs 4 (rather, a helical circumferential continuous rib 4); in a corresponding manner leave the wells 3 between them wells 5, which partially overlaps with the ribs 4 due to the mutual overlap of the wells.

In FIG. 1b ) is the surface of the reinforcing rod according to the invention from the vertical section recognizable with the rod diameter d ₂ in the region of the recess 2 and the rod diameter d ₃ in the region of the recess 3. Also two details A, B, in the FIGS. 1e) and 1f ), the different ribs or recesses illustrate: Both recesses have the same flank angles α and the same radii of curvature R ₁ in the transition region between recessed bottom 2a, 3a and rib flanks 2b, 3b. Only the rib depths t ₂ , t ₃ and the recess widths b ₂ , b ₃ are just as different as the rib pitches T ₂ , T ₃ (see FIG FIG. 1a )).

If you look at the horizontal section in the Figures 1c) and 1d ), it can be seen that the recesses 2, 3 or ribs 4, 5 overall result in an inhomogeneous surface of the reinforcing bar 1, which is responsible for different areas have different shear loads and thus overall resilience of the reinforcing bar can be improved ,

The FIGS. 2a) and 2b ) show an alternative reinforcing bar 21 with recesses 22, 23 which extend helically along the reinforcing bar 21 in the same direction and have different slopes. This also makes it possible to produce ribs with different geometric properties, which have different shear stresses on the ribbed bottom.

In the FIGS. 3a) and 3b A reinforcing bar 31 is shown in which ribs with different geometric properties merge into each other: while the rib pitch T ₄ , ie the distance between adjacent screw flights of the helical circumferential rib is the same across the entire reinforcing bar, the depth t ₄ , t _{5 changes} the recess 22 over the axial length of the rod. As a result, quasi ribs 24, 25 with different geometric properties are continuous and stepless into each other and have due to the different rib depth t ₄ , t ₅ accordingly different load capacities.

Based on FIGS. 4 to 7 can illustrate the system of rib designs: So shows FIG. 4 a reinforcing bar 41 having a first order rib 42 and a recess 43 having a rib depth t ₄₂ , a blade pitch angle α, a pitch T ₄₂ composed of the rib width B ₄₂ plus the distance b ₄₂ between two adjacent ribs.

In FIG. 5 is now at a reinforcing rod 51 of the first-order rib 42 from FIG. 4 corresponding rib and one of the recess 43 FIG. 4 corresponding recess a narrower rib 52 second order and narrower recesses 53 superimposed, which together with the first-order rib form an order system of narrow ribs of higher order 52, 54, 55, 56 and a wide rib 57 lower order, which carries the narrow ribs. It is easy to see that in a load case, the narrow ribs shear off faster and that their shearing the wide rib 57 still forms a bond with the concrete surrounding the reinforcing rod and thus the rod 51 does not suddenly fail in all anchoring sections simultaneously.

FIG. 6 and FIG. 7 Finally, even with rebars 61, 71 are multi-stage ribs 62, 72, which are also the result of the superposition of multiple ribs, the rib portions 62a, 62b, 62c different edge slopes α ₀ , α ₁ and α ₂ and different rib widths B ₀ , B ₁ , B ₂ have. By contrast, the multi-stage rib 72 is off FIG. 7 the transition between the sections of the rib continuously with continuous width and angle change.

The multistage ribs also lead to the fact that, in case of doubt, first the narrowest sub-rib 62c shears off earlier than the widest sub-rib 62a and thus likewise provides for an improvement in the loading capacity of the associated reinforcing rod 61.

In summary, the present invention offers the advantage of improving the composite behavior of fiber-reinforced plastic reinforcing rods by forming ribs with different geometric and / or material properties, to optimize their application behavior under load and thus to make such plastic reinforcing rods further applications possible. Accordingly, a fiber reinforced plastic reinforcing bar is provided which helps reduce the crack spacing and crack width in the concrete surrounding the reinforcing bar, resulting in the advantages described.

Claims (8)

Reinforcing bar made of fiber-reinforced plastic, provided on its peripheral surface with a radially outwardly projecting profiling in the form of extending over at least part of the circumference ribs,
characterized,
that the reinforcing bar ribs (4, 5, 42, 52, 54, 55, 56, 57, 62, 72) having different geometrical and / or material properties. Reinforcing bar according to at least Claim 1,
characterized,
that the ribs (4, 5, 42, 52, 54, 55, 56, 57, 62, 72) are designed with different geometrical and / or material properties that they have a different shear stress at the rib base in the case of load. Reinforcing bar according to at least Claim 1,
characterized,
that the ribs (4, 5, 42, 52, 54, 55, 56, 57, 62, 72) are designed with different geometrical and / or material properties that they do not fail time and / or load the same in the case of load. Reinforcing bar according to at least one of the preceding claims,
characterized,
that the ribs (4, 5, 42, 52, 54, 55, 56, 57, 62, 72) with different geometrical and / or material properties at least approximately in the same axial portion of the reinforcing bar adjacent to each other, adjacent to each other, with mutual spacing and / or are mutually overlapping ,. Reinforcing bar according to at least one of the preceding claims,
characterized,
that the geometric and / or material properties of the ribs (4, 5, 42, 52, 54, 55, 56, 57, 62, 72) over the axial length of the reinforcing rod (1, 21, 31, 41, 51, 61, 71 ) and / or its circumference are formed in several stages. Reinforcing bar according to at least one of the preceding claims,
characterized,
that the different selectable geometric properties of the ribs (4, 5, 42, 52, 55, 56, 57, 62, 72) rib height (t), rib spacing (b), rib pitch (T), inclination angle (α) of the rib flanks, slope the ribs and / or rib shape include. Reinforcing bar according to at least one of the preceding claims,
characterized,
that the different material properties of the fins different fiber content, different materials of rebar and / or fibers and / or different fiber orientations include. Reinforcing bar according to at least one of the preceding claims,
characterized,
in that ribs (62a, 62b, 62c) are combined to form a multi-stage rib (62) that builds on one another in the radial direction, in which a plurality of ribs with different geometrical and / or material properties are arranged at least partially overlapping one another or overlapping.

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