EP1025323B1 - Method for strengthening and/or restoring reinforced or prestressed concrete supporting structures, and device for carrying out said method - Google Patents

Abstract

A reinforced or prestressed concrete structure is strengthened and/or restored by attaching a strip-shaped tensional member thereto. Prior to attaching the tensional member, a central portion thereof is prestressed. Then, the tensioned central portion is bonded to a concrete surface of the concrete structure by a first adhesive having a high deformation modulus. Thereafter, the non-prestressed end portions of the tensional member are bonded to the concrete surface by a second adhesive having a low deformation modulus, whereby the second adhesive is substantially less deformable than the first adhesive.

Description

The invention relates to a method for upgrading and / or renovating reinforced concrete or prestressed concrete structures according to the preamble of claim 1.

To increase the load-bearing capacity (strengthening) or to restore the original load-bearing capacity (renovation) of structures made of reinforced concrete or prestressed concrete, it is known to subsequently attach prestressed tension members to the outside of the structures. To anchor them, for example, brackets made of steel or reinforced concrete are anchored to the concrete surface, and the tension member is stretched between these brackets. Due to the offset between the axis of the tension member and the concrete surface, however, an unfavorable offset moment arises, which has to be recorded in the bracket anchoring and forwarded; in addition, a bond between the tension member and the concrete surface can not be made.

In order to avoid these disadvantages caused by the offset between the tension member and the concrete surface, it is known in a method of the type mentioned at the outset to subsequently tape-like tension members to the concrete surface in order to improve and / or to rehabilitate reinforced concrete or prestressed concrete structures. Such a continuous Adhesive bond is particularly important if there are cracks in the concrete or can occur and if the opening of these cracks is to be hindered.

If tension members are glued to a concrete surface in a tensioned state, the adhesive joint is permanently stressed by the shear force resulting from the introduction of the prestressing force. In order to avoid creeping losses due to this shear stress on the adhesive joint, adhesives with a deformation module that is as low as possible are used, which result in a largely rigid adhesive joint in the hardened state.

For handling reasons, high-strength, thin and therefore comparatively light strips are preferably used as tension members. These bands of high-strength materials usually behave linearly elastic until they break; a flowing plateau; i.e. an area with constant force approximated by the expansion path does not appear with such high-strength materials.

If such band-shaped prestressed tension members bridge cracks in the concrete surface that open when the structure is loaded, there is a risk in the rigid adhesive bond described that the tension member is stretched beyond the two cracks in the crack area to such an extent that there is a sudden Break comes without this announcing itself in the form of a plastic deformation.

This lack of ductility is disadvantageous and considerably limits the possible degree of utilization of the tension members. Therefore, in areas where cracks have to be bridged, an adhesive composite can be selected which itself has a certain deformability, ie has a high deformation modulus, so that in the event of a crack opening, expansion compensation in the tension member can take place over a length which is significantly greater than the increase in the crack width. Such adhesive composite with a high deformation modulus are unsuitable as permanent anchoring because of the creep losses associated therewith.

In addition, there is the problem that the tensile forces must be introduced into the substructure at the ends of prestressed tension members. In conventional prestressed concrete constructions, a so-called rear reinforcement is provided for this, which prevents the formation of cracks immediately behind the tendon anchor. Such a reinforcement is also required for pre-stressed tension members.

In a known method of the type mentioned at the beginning (WO 97/21009, Fig. 5), a tension member, which has fiber components, is prestressed in a central region of its length and glued to the concrete surface of a supporting structure. In its two end regions, the tension member is received in a clamping device which is connected to the supporting structure via a plastically deformable transmission element. The plastically deformable transmission element forms a composite, the deformation modulus of which is significantly higher than that of the adhesive composite in the central region of the tension member. Since the anchoring of the traction means at its end regions only becomes effective when the traction means is overloaded over its entire central region, ie not in the event of local overloads, the risk of breakage in the area of cracks is not avoided.

The object of the invention is to overcome the disadvantages mentioned and to provide a method for retrofitting and / or renovating reinforced concrete or prestressed concrete structures in which the risk of breakage in the range of avoiding an offset moment when the band-shaped tension member is directly applied to the concrete surface Cracks avoided, but creep losses are excluded at the same time.

This object is achieved in that the second deformation module is significantly lower than the first deformation module.

In the prestressed area, which extends over most of the length of the tension member, no shear forces are inherently transmitted between the tension member and the concrete surface via the compound. Only when there are strains and, in particular, cracks in the concrete, there are shear forces transmitted between the tension member and the concrete surface in localized areas. However, since a comparatively shear-resistant composite is used in this central region of the tension member, expansion compensation takes place in the tension member across the crack width, so that an overall ductile process is established.

The non-prestressed protrusion in the two end areas of the tension member serves as anchoring and reinforcement. Since an adhesive composite with a low deformation modulus, ie a largely rigid adhesive composite is used in this non-prestressed area, the prestressing force is largely transferred into the concrete without creep losses.

The surface-flush arrangement of the band-shaped tension member prevents the occurrence of an offset moment. A separate anchoring and back-up reinforcement is not necessary, since these functions are achieved in a particularly simple and space-saving manner by the rigid adhesive connection of the non-prestressed end regions of the traction means to the concrete surface.

Further advantageous embodiments of the method according to the invention are the subject of subclaims.

The invention further relates to a device for carrying out the method with a band-shaped tension member to be arranged on the concrete surface of the structure, tensioning devices and end anchors acting thereon, the tensioning device having a force introduction body which is non-positively connected to the band-shaped tension member and which, in the longitudinal direction of the tension member, is fixed to the structure is displaceable, and wherein a tension drive can be used between the force introduction body and the base body. Such a device is shown in WO 99/10 613, which does not belong to the previously published prior art. According to the invention, at least one spacer is inserted between mutually facing abutment surfaces of the base body and the force introduction body.

This tensioning device, which is arranged at one or preferably at both ends of the central, prestressed area of the tension member, creates the possibility in a structurally simple and space-saving manner to apply the required pretensioning force to the middle area of the tension member, the two end areas lying beyond the force introduction points of the tension member remain unstressed.

Advantageous embodiments of the device according to the invention are the subject of further subclaims.

An exemplary embodiment of the invention is illustrated below, which is shown in the drawing.

• Fig. 1 in vereinfachter Darstellungsweise ein Stahlbeton- oder Spannbeton-Tragwerk mit einem aufgebrachten Zugglied,
• Fig. 2 in einer Ansicht in Richtung des Pfeiles II in Fig. 1 eine an der einen Krafteinleitungsstelle des Zuggliedes. angeordnete Spannvorrichtung im Ausgangszustand,
• Fig. 3 die Spannvorrichtung nach Fig. 2 nach dem Vorspannvorgang,
• Fig. 4 eine Ansicht der Spannvorrichtung in Richtung des Pfeiles IV in Fig. 2,
• Fig. 5 eine Ansicht der Spannvorrichtung in Richtung des Pfeiles V in Fig. 3,
• Fig. 6 die Spannvorrichtung nach den Fig. 2-5 in einer Explosionsdarstellung,
• Fig. 7 in einer Darstellung entsprechend der Fig. 1 ein Stahlbeton- oder Spannbeton-Tragwerk mit einem nach einem abgewandelten Verfahren aufgebrachten Zugglied und
• Fig. 8 in einem schematischen Längsschnitt die Enden mehrerer aufeinanderliegender Zugglieder.

It shows:

• 1 is a simplified representation of a reinforced concrete or prestressed concrete structure with an attached tension member,
• Fig. 2 in a view in the direction of arrow II in Fig. 1 one at the force introduction point of the tension member. arranged clamping device in the initial state,
• 3 shows the tensioning device according to FIG. 2 after the prestressing process,
• 4 is a view of the tensioning device in the direction of arrow IV in FIG. 2,
• 5 is a view of the clamping device in the direction of arrow V in Fig. 3,
• 6 shows the clamping device according to FIGS. 2-5 in an exploded view,
• Fig. 7 in a representation corresponding to FIG. 1, a reinforced concrete or prestressed concrete structure with a tension member applied by a modified method and
• Fig. 8 in a schematic longitudinal section, the ends of several superimposed tension members.

For strengthening or renovating a reinforced concrete or prestressed concrete structure 1, a band-shaped tension member 3 is applied to the concrete surface 2, which consists, for example, of carbon fibers. The central area 3a of the tension member 3 is prestressed between two force introduction points 4 by a prestressing force indicated by arrows 5 in FIG. 1. The tension member 3 is not prestressed in its two end regions 3b located beyond the force introduction points 4.

In its central, prestressed area 3a, the band-shaped tension member 3 is connected to the: concrete surface 2 by means of a first adhesive compound which has a relatively high modulus of deformation. In its two end regions 3b, the tension member 3 is connected to the concrete surface 2 by means of a second adhesive compound, which has a deformation module that is considerably lower than that; this second adhesive compound is largely rigid in the hardened state.

If a crack 6 present or occurring in the concrete surface 3 opens when the structure 1 is loaded, an expansion compensation takes place in the tension member 3 on both sides of the crack 6 due to the deformability of the adhesive composite.

To apply the pretensioning force for the central region 3a of the tension member 3, a tensioning device 7 is arranged at each of the two force introduction points 4, as is shown in FIGS. 2-6.

Each tensioning device 7 has a plate-shaped base body 8 which is fastened to the base of a flat recess 9 of the concrete surface 2, preferably glued on.

A T-shaped force introduction body 10 is attached with its T-stem 10a to the underside of the band-shaped tension member 3, preferably glued and is arranged in a recess 11 of the base body 8, that the force introduction body 10 also in the recess 9 of the Concrete surface 2 is sunk. The connecting surface, which is preferably connected by adhesive bond to the tension member 3, ie the upper side of the T-arm 10a of the force introduction body 10 lies in the plane of the concrete surface 2.

• 1. Der T-Stiel 10a kann länger als dargestellt ausgeführt werden;
• 2. ein zweiter T-förmiger Krafteinleitungskörper (nicht dargestellt) kann auf der dem ersten Krafteinleitungskörper 10 gegenüberliegenden Seite angeordnet und mit dem Zugglied 3 sowie dem Krafteinleitungskörper 10 verbunden, vorzugsweise verklebt werden;
• 3. zur Verbesserung der Krafteinleitung in das bandförmige Zugglied 3 können Lamellen, beispielsweise Stahllamellen, mit dem Zugglied 3 verklebt und mit dem Krafteinleitungskörper 10 verbunden, beispielsweise ebenfalls verklebt oder formschlüssig verbunden werden.

The connection between the T-shaped force introduction body 10 and the band-shaped tension member 3 can alternatively also be carried out as follows:

• 1. The T-arm 10a can be made longer than shown;
• 2. a second T-shaped force introduction body (not shown) can be arranged on the side opposite the first force introduction body 10 and connected, preferably glued, to the tension member 3 and the force introduction body 10;
• 3. To improve the introduction of force into the band-shaped tension member 3, lamellae, for example steel lamellae, can be glued to the tension member 3 and connected to the force introduction body 10, for example also glued or positively connected.

A hydraulic or mechanical tensioning element of a tensioning drive 12, which is supported on the base body 8, acts on the two T-arms 10b of the force introduction body 10. In the exemplary embodiment shown, the tensioning drive 12 has two hydraulic tensioning cylinders 12a arranged on both sides of the T-arm 10a, which act on the two T-arms 10b. An angular cover 13 is connected to the base body 8 and serves to fasten the tensioning drive 12.

After application, the tension member 3 is prestressed in its central region 3a on the concrete surface 2 before the first adhesive compound has hardened between the tensioning drives 7 of the two force application points 5.

In order to mechanically positively fix the tension member 3 at at least one, but preferably at the two force application points 4 after the application of the prestressing force with respect to the concrete surface, at least one spacer 14 is used between mutually facing abutment surfaces 10c of the force introduction body 10 and abutment surfaces 8a of the base body 8. In the illustrated embodiment, the spacers 14 consist of a plurality of sheet metal pieces with which the force introduction body 10 is wedged relative to the base body 8.

After wedging, the tensioning drive 12 can be removed from the tensioning device 7 in order to be used for prestressing another tension member.

Preferably, the force introduction body 10 is also provided on its underside with an adhesive compound which hardens to a largely rigid adhesive connection after the tensioning process.

The end regions 3b of the tension member 3 are fixed to the concrete surface 2 by means of an adhesive compound which is largely rigid after hardening. The end regions 3b attached to the concrete surface 2 thus form a reinforcement for the two ends of the tension member 3.

In the exemplary embodiment according to FIG. 1 described so far, the pretensioning force for the central region 3a was introduced at two force introduction points 4 each lying between the central region 3a and the subsequent end region 3b. Deviating from this, it is shown in FIG. 7 that the pretensioning force 5 can be introduced via force introduction points 4 'located at the ends of the tension member 3 after the first adhesive composite has been applied only in the central region 3a. After this first adhesive composite has hardened, the ends of the tension member 3 are detached, for example cut off, from the tensioning devices arranged at the force introduction points 4 '. The end regions 3b of the tension member 3 are folded up, provided with the second adhesive composite and fixed to the concrete surface 2 with this.

In Fig. 8 it is shown that several band-shaped tension members 3, 3 'can be applied one after the other. First, the lowest band-shaped tension member 3 is applied to the concrete surface 2 in the manner already described. After the adhesive composite has hardened under the central region 3a and the end region 3b, a second band-shaped tension member 3 'is again placed on the top of the first band-shaped tension member 3 with an adhesive composite with a high deformation modulus (represented by a wavy line). The clamping devices 7 arranged at the two ends apply the required pretensioning force.

After the adhesive compound has hardened under the central region 3a ', the end of the tension member 3' is separated from the tensioning device 7 in the manner described. The end regions 3b 'are folded up, coated with the adhesive compound with a low deformation modulus and glued to the concrete surface 2.

This process can be repeated several times in order to apply a plurality of tension members one above the other, the end regions 3b, 3b '... Being rigidly attached directly to the concrete surface 2.

After all tension members 3, 3 '... have been applied, the tensioning device 7 can be completely detached from the concrete surface 2; instead, only the base plate 8 can remain, while all other parts of the clamping device 7 are removed.

Claims (12)

1. Method of strengthening and/or rehabilitating reinforced or prestressed concrete supporting structures, in which a strip-like tension member (3) is pretensioned in a central region (3a) of its length and is bonded to the concrete surface (2) of the supporting structure (1) by means of a first bonding agent having a first modulus of deformation and is bonded at its two end regions (3b) in the non-pretensioned state to the concrete surface (2) by means of a second bonding agent having a second modulus of deformation, characterized in that the second modulus of deformation is significantly lower than the first modulus of deformation.
2. Method according to Claim 1, characterized in that the first and/or the second bonding agent is or are each an adhesive bonding agent.
3. Method according to Claim 2, characterized in that, after the application of its central region (3a) to the concrete surface (2), the tension member (3) is pretensioned between the two force application points (4) prior to the curing of the first adhesive bonding agent.
4. Method according to Claim 1, characterized in that the pretensioning force for the central region (3a) is introduced at two force introduction points (4) each situated between the central region (3a) and the adjoining end region (3b).
5. Method according to Claim 1, characterized in that the first adhesive bonding agent is applied only in the central region (3a), in that the pretensioning force is introduced by way of force introduction points (4') situated at the ends of the tension member (3), in that the ends of the tension member (3) are released from the force introduction points (4') after the curing of the first adhesive bonding agent, and in that the end regions (3b) of the tension member (3) are secured on the concrete surface (2) by means of the second adhesive bonding agent.
6. Method according to Claim 4, characterized in that the tension member (3) is secured in a mechanically form-fitting manner with respect to the concrete surface (2) at at least one of the two force application points (4) after the application of the pretensioning force.
7. Method according to one of Claims 1-6, characterized in that a plurality of strip-like tension members (3, 3') are successively applied one above the other.
8. Method according to Claim 4, characterized in that, prior to the pretensioning at the force application point (4), the tension member (3) is connected by adhesive bonding to a force introduction element (10) which can be displaced relative to the concrete surface (2).
9. Device for carrying out the method according to one of Claims 1-7 using a strip-like tension member (3) to be arranged on the concrete surface of the supporting structure, tensioning devices acting on said tension member, and end anchorages, wherein the tensioning device (7) comprises a force introduction element (10) which is connected in a force-fitting manner to the strip-like tension member (3) and can be displaced in the longitudinal direction of the tension member (3) relative to a basic body (8) fastened to the supporting structure (1), wherein a tensioning drive (12) can be fitted between the force introduction element (10) and the basic body (8), and wherein at least one spacer (14) is fitted between mutually facing abutment faces (8a, 10c) of the basic body (8) and of the force introduction element (10).
10. Device according to Claim 9 in combination with a concrete surface, characterized in that the basic body (8) and the force introduction element (10) are sunk within a clearance (9) in the concrete surface (2) in such a way that a connecting surface, which is connected to the tension member (3) preferably by adhesive bonding, lies in the plane of the concrete surface (2).
11. Device according to Claim 9, characterized in that the force introduction element (10) is T-shaped in outline and is connected, preferably adhesively bonded, to the tension member (3) by way of its T-leg (10a), and in that a hydraulic or mechanical tensioning element of the tensioning drive (12) acts on each of the two T-arms (10b).
12. Device according to Claim 11, characterized in that the T-arms (10b) form the abutment faces (10c) for the inserted spacers (14).