EP1397569B1 - Anchorage fixture for a strip-type tension member, used in the building trade - Google Patents

Abstract

A tie anchor for strip-type tension members includes an anchor body disposed on at least one side of the tension member. The anchor body includes a plurality of clamping blocks arranged at a distance from each other in a longitudinal direction of the tension member. The clamping blocks are connected to tension member by adhesive and/or friction (clamping friction). An end-most (final) one of the clamping blocks is attached to a fixed abutment. Adjacent clamping blocks are interconnected by expansion members whose spring stiffness becomes progressively stronger toward the end-most clamping block.

Description

The invention relates to a clamping anchor for band-shaped tension members in construction, in particular fiber-reinforced plastic slats, with at least one frictionally connected to the tension member by gluing and / or friction anchor body, which is supported on a stationary abutment.

To increase the sustainability (retrofitting) or restore the original capacity (rehabilitation) of structures made of reinforced concrete or prestressed concrete, it is known to subsequently attach to the outside of the structures prestressed band-shaped tension members. Apart from steel lamellae, fiber-reinforced plastic lamellae are preferred, in particular carbon fiber reinforced plastics (CFRP), aramid reinforced plastics (AFK) and glass reinforced plastics (GRP).

An important feature of these fiber-reinforced plastics, in particular of the carbon fiber-reinforced plastics used with preference, is that the band-shaped tension members produced therefrom exhibit a behavior which is linearly elastic up to breakage. When anchoring the ends of the tension members, care must be taken to maintain a uniaxial tension condition. A biaxial tensile stress condition caused by substantial stress peaks at the clamping point and / or a deflection would lead to damage or even destruction of the band-shaped tension member.

In the adhesive attachment of the band-shaped tension members to the anchor bodies, the transition from the free span of the tension member to the anchoring zone is a discontinuity in terms of stiffness. Since the activatable adhesive length, which absorbs by shear stress introduced by the tension member load is relatively short, it comes at the transition from the free span length to the anchoring zone to a shear stress peak, which exceeds the locally permissible shear stress in the bonding joint and reaches the fracture stress. The decisive breaking criterion for adhesion is in this case an exceeding of the cohesion of the adhesive and / or the breakage of the plastic matrix of the band-shaped tension member. The fracture shear stress front formed thereby travels along the glue joint until the adhesive bond completely fails.

Although it is known (DE 198 49 605 A1), to increase the adhesive effect to apply an additional clamping force between the anchor body and the tension member glued thereto. The resulting biaxial stress state (longitudinal tension / limited transverse pressure) is harmless for the tension member, since no transverse tension occurs. Rather, there is an increase in the relevant breaking strength. The shear stress peak at the transition from the free span length to the anchoring zone is not reduced thereby.

To solve this problem by reducing or avoiding a shear stress peak at the transition from the free span length in the anchoring zone is already It has been proposed to change the adhesive properties along the force introduction path such that a relatively soft adhesive (low shear modulus) is used at the transition to the anchorage and the adhesive properties to the other end of the anchorage are changed so that the adhesive has a high shear modulus and therefore substantially looks stiffer. However, the selection of the adhesive materials and in particular the observance of the prescribed conditions when applying the adhesive make very high demands and are especially not subsequently controllable.

It is also known to insert a perforated plate or a similar material in the glue joint. As a result, an overall lower shear modulus of the adhesive joint is achieved without affecting the overall load capacity. As a result, the harmful shear stress peak can indeed be reduced, but not sufficient for many applications.

The object of the invention is, therefore, a tension anchor of the type mentioned in such a way that the emergence of the breaking stress in the adhesive joint or in the friction region locally exceeding shear stress peak is avoided.

Starting from the preamble of claim 1, this object is achieved in that the anchor body has a plurality, in the longitudinal direction of the tension member spaced from each other, connectable to the tension member by gluing and / or friction terminal blocks, wherein the end of the tension member last terminal block on stationary abutment can be supported, that the clamping blocks are connected by Dehnabschnitte different spring stiffness and that the spring stiffness of the Dehnabschnitte increase toward the end of the tension member.

Thus, although a stepped, but still sufficiently evenly until the transition from the free span length to the anchoring zone sloping gradient of the transmitted tensile force in the adhesive joint or in the friction region is achieved. The shear stress is so far reduced to the transition to the free span length of the tension member, that at this point neither the cohesion of the adhesive or the maximum possible frictional force is exceeded, nor damage to the tension member occurs.

According to a preferred embodiment of the invention it is provided that in each case an anchor body is arranged on both sides of a band-shaped tension member or a layer of two band-shaped tension members whose respective superimposed clamping blocks are interconnected by clamping elements. Preferably, the clamping elements on both sides next to the tension member arranged lag screws.

The arranged between the individual terminal blocks, different elastic, ie running with different spring stiffness Dehnabschnitte be executed structurally particularly simple and easy to manufacture manner as connecting webs with different web cross-section. The different web cross-section, which is based on several subsequently described types can be achieved leads to different spring stiffness. This can be realized in a very simple manner, the requirement to increasingly perform the spring stiffness of the Dehnabschnitte from the point of entry of the tension member to its end.

Further advantageous embodiments of the inventive concept are the subject of further subclaims.

• Fig. 1 in einem Längsschnitt eine stark schematisierte Darstellung eines Spannankers für ein bandförmiges Zugglied, wobei für die Dehnabschnitte unterschiedlicher Federsteifigkeit Federsymbole verwendet werden,
• Fig. 2 eine Draufsicht auf den schematisch dargestellten Spannanker gemäß Fig. 1,
• Fig. 3 eine Draufsicht auf ein Ausführungsbeispiel eines Spannankers für ein bandförmiges Zugglied,
• Fig. 4 eine Seitenansicht des Spannankers gemäß Fig. 3, wobei die Abstützung an einem ortsfesten Widerlager der deutlicheren Darstellung halber weggelassen ist,
• Fig. 5 eine räumliche Darstellung des Spannankers gemäß Fig. 4,
• Fig. 6 eine Draufsicht auf einen Spannkörper gemäß einer ersten Ausführungsform,
• Fig. 7 einen Schnitt längs der Linie VII-VII in Fig. 6 und
• Fig. 8-15 weitere Ausführungsbeispiele in Darstellungen entsprechend den Fig. 6 und 7.

Embodiments of the invention will be explained in more detail, which are illustrated in the drawing. It shows:

• 1 is a longitudinal section of a highly schematic representation of a clamping anchor for a band-shaped tension member, being used for the Dehnabschnitte different spring stiffness spring symbols
• 2 is a plan view of the schematically illustrated clamping anchor of FIG. 1,
• 3 is a plan view of an embodiment of a clamping anchor for a band-shaped tension member,
• 4 shows a side view of the tensioning anchor according to FIG. 3, wherein the support on a stationary abutment has been omitted for the sake of greater clarity,
• 5 is a perspective view of the clamping anchor of FIG. 4,
• 6 is a plan view of a clamping body according to a first embodiment,
• Fig. 7 is a section along the line VII-VII in Fig. 6 and
• 8-15 further embodiments in illustrations corresponding to FIGS. 6 and 7.

1 and 2, the basic structure of a tensioning anchor for band-shaped tension members 1 is schematically explained, for example, of lamellae made of carbon fiber reinforced plastic (CFRP lamellae). This band-shaped tension members 1 are used in construction for retrofitting or rehabilitation of prestressed concrete or reinforced concrete structures. The band-shaped tension members, for example, glued to the concrete surface or remain without bonding with the concrete surface. The clamping anchors described serve to apply a bias voltage and / or to the final anchoring of the tension members.

For this purpose, an anchor body 2 is connected by gluing and clamping with the tension member 1. Instead, the bond can also be done by friction. As one of the possible embodiments, the adhesive bond is described below. The anchor body 2 has a plurality of, in the longitudinal direction of the tension member 1 at a distance from each other arranged clamping blocks 3. Each of the clamping blocks 3 is connected via an adhesive layer 4 by gluing to the tension member 1. By means of clamping screws 5, which are indicated only schematically in Fig. 1, is each Terminal block connected to a clamping counterpart 6. These clamping counterparts 6 can in turn (not shown) be parts of a second clamping body 2 on the underside of the tension member 1.

The last terminal block 3 towards the end of the tension member, in the illustrated embodiment the leftmost terminal block 3, is attached to a stationary, i.e. Supported abutment 7 supported on the structure, for example via a hydraulic tensioning device. 8

Dehnabschnitte 9 are formed between the individual terminal blocks 3, which are symbolized in the illustration of FIGS. 1 and 2 as groups of tension springs. The different thickness of the tension springs represents that the Dehnabschnitte 9 are designed with different spring stiffness, the spring stiffness of the transition point 10 from the free span length of the tension member 1 in the anchoring zone to the end of the tension member (left in Figs. 1 and 2) increases ,

The spring stiffness of the Dehnabschnitte 9 are chosen and graded so that the introduction of force into each terminal block 3, which takes place on shear stresses in the adhesive layer 4, excludes the emergence of shear stress peaks that would exceed the maximum shear stress in the adhesive and would lead to a cohesion failure. Deviating from the embodiments shown in the drawing, an adhesion can also take place in the region of the expansion sections 9.

The different spring stiffness of the Dehnabschnitte 9 can be achieved structurally in different ways; preferred examples thereof are shown in the following figures.

In the embodiment of a tension anchor for tension members 1, for example carbon fiber reinforced plastic slats shown in FIGS. 3-5, an anchor body 2 is arranged on both sides of a layer of two band-shaped tension members 1, each of which superposed terminal blocks 3 each by laterally adjacent to the tension members. 1 arranged lag screws 5 are connected and clamped together. For uniform application of force, the lag screws 7 each act on a transverse yoke 11 via two adjacent support points 11a, 11b on the respective terminal block 3. Instead, a single, central support point can be selected. Multiple, individually functioning identical tie rods can be combined as modules to form a larger tendon by stacking using longer, common screws 7.

The end of the tension member 1 towards last terminal block 3 is connected to a head plate 2 a of the anchor body 2. This top plate 2a is supported on the stationary abutment 7 via lateral hydraulic clamping cylinder 8.

The Dehnabschnitte 9 between the clamping blocks 3 are formed by connecting webs 13 which are the same width, but different thickness. The thickness of the Connecting webs 13 increases from the transition point 10 to the top plate 2a and thus to the end of the tension member 1 to.

Fig. 6 shows a plan view in a simplified representation of the basic structure of the anchor body 2, as it is used in the embodiment of FIGS. 3-5. In the same representation, further embodiments are shown in Figs. 8-15.

In the example according to FIGS. 8 and 9, the expansion sections 9 between the clamping blocks 3 forming connecting webs each consist of a plurality of web portions 14 which are separated by recesses, in the example of FIGS. 8 and 9 perpendicular to the band-shaped tension member 1 extending holes 15 are. In each case the total web cross-section of all web sections 14 of the individual expansion sections 9 is different. As shown in FIGS. 8 and 9, the bores 15 have the largest diameter in the expansion section 9 closest to the transition point 10, so that the total cross-section of all the web sections 14 is the smallest here. In the next following expansion section 9, the diameter of the holes 15 are smaller; thus here the total web cross-section is larger. Finally, the diameter of the bores 15 in the end of the tension member 1 towards the next expansion section 9 is even lower and the total web cross-section is larger.

The embodiment of FIGS. 10 and 11 differs from the previously described embodiment substantially only in that the the web portions 14 'of each expansion section 9 separating holes 15' extend parallel to the surface of the band-shaped tension member 1 and transverse to its longitudinal direction. Each bore 15 'separates two web sections 14' from one another in each expansion section 9. Here, too, the diameter of the bores 15 'decreases starting from the transition point 10, while the total web cross-section of the web sections 14' increases.

In the embodiment according to FIGS. 12 and 13, a bending section 16 directed transversely to the longitudinal direction of the tension member 1 is formed in each expansion section 9. The bending sections 16 of the individual expansion sections 9 have different bending stiffnesses.

The bending sections 16 or bending beams are each formed between a slot 17 extending from the tension member 1 and a slot 17 extending into the anchor body 2 from the opposite side.

As a result of the depth of the slots 17 decreasing from the transition point 10, the effective length of the bending sections 16 decreases. At the same time, it is achieved that the thickness of the bending sections 16 increases as a result of the distance of the respectively adjacent slots 17 increasing starting from the transition point 10. Both individually or in combination applicable measures cause the spring stiffness of the bending sections 16, starting from the transition point 10 to the end of the tension member 1 increases towards.

In the embodiment according to FIGS. 14 and 15, the expansion sections 9 exist between the clamping blocks 3 Material with different modulus of elasticity (modulus of elasticity). Starting from the transition point 10, the modulus of elasticity of the material used for the expansion sections 9 increases, ie the spring stiffnesses of the expansion sections 9 increase toward the end of the tension member 1.

The graded gradient of the anchor stiffness with the division into "load transfer zones" by composite and "expansion zones" preferably without composite, serves to divert only as much tensile force per load application zone from the lamella as transmitted by the selected composite principle (bonding + transverse pressure or friction + lateral pressure) can, without harm. Thereafter, this load transfer zone eludes further stresses by stretching the expansion zone beyond it, and the next load transfer zone is activated. Ideally, each load transfer zone derives a certain proportion of the total pulling force from the tension member. These are then collected in the anchor part until they are finally handed over to the component. The necessary expansions in the expansion zones must be achieved by adapted spring stiffnesses. The number of "clamping blocks" to be connected in series is then determined by the size of the load in the tension member and the permissible stress of the selected composite principle (adhesion / cohesion or pure friction of anchor surfaces with the tension member). Thus, compared to a conventional bond without alternating arrangement of load introduction and expansion compensation, the adhesive joint is activated over the entire length.

Claims (12)

1. Anchorage fixture for strip-shaped tension members in the construction industry, especially fibre-reinforced plastic laminae, having at least one anchor body which can be non-positively connected by adhesion and/or friction to the tension member and which can be supported against a fixed abutment, characterized in that the anchor body (2) has a plurality of clamping blocks (3) which are arranged spaced apart in the longitudinal direction of the tension member (1) and can be connected by adhesion and/or friction to the tension member (1), the last clamping block (3) in the direction of the end of the tension member (1) being able to be supported against the fixed abutment (7), in that the clamping blocks (3) are connected one to another by expansion segments (9) of different spring stiffness, and in that the spring stiffnesses of the expansion segments (9) increase in the direction of the end of the tension member (1).
2. Anchorage fixture according to Claim 1, characterized in that on both sides of a strip-shaped tension member (1) or of a layer of two strip-shaped tension members (1) there is respectively disposed an anchor body (2), whose clamping blocks (3) situated respectively one above the other are connected one to the other by clamping elements (5).
3. Anchorage fixture according to Claim 2, characterized in that the clamping elements are tension bolts (5) disposed next to the tension member (1) on both sides.
4. Anchorage fixture according to Claim 1, characterized in that the expansion segments (9) between the clamping blocks (3) are connecting webs (13, 14, 14') of different web cross section.
5. Anchorage fixture according to Claim 4, characterized in that all the connecting webs (13) are equally wide, yet varyingly thick.
6. Anchorage fixture according to Claim 4, characterized in that the connecting webs respectively consist of a plurality of web segments (14, 14') separated from one another by recesses (15, 15'), and in that the total web cross section of the individual expansion segments (9) is in each case different.
7. Anchorage fixture according to Claim 6, characterized in that the recesses separating the web segments (14) are bores (15) running perpendicular to the strip-shaped tension member (5).
8. Anchorage fixture according to Claim 6, characterized in that a bore (15') running parallel to the surface of the strip-shaped tension member (1) and transversely to its longitudinal direction respectively separates two web segments (14') one from the other.
9. Anchorage fixture according to Claim 1, characterized in that in each expansion segment (9) there is configured a bending segment (16) directed transversely to the longitudinal direction of the tension member (1) and the bending segments (16) of the individual expansion segments (9) have different bending stiffnesses.
10. Anchorage fixture according to Claim 9, characterized in that the bending segments (16) are configured respectively between a slot (17) extending from the tension member (1) and slot (17) extending from the opposite side into the anchor body (2).
11. Anchorage fixture according to Claim 10, characterized in that the bending segments (16) are varyingly thick and/or varyingly long.
12. Anchorage fixture according to Claim 1, characterized in that the expansion segments (9) consist of material with different modulus of elasticity.

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