EP4071321B1 - Système et procédé pour structures de renforcement avec stratifiés de polymère renforcé de fibres pré-contraints - Google Patents

Système et procédé pour structures de renforcement avec stratifiés de polymère renforcé de fibres pré-contraints Download PDF

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Publication number
EP4071321B1
EP4071321B1 EP21167213.4A EP21167213A EP4071321B1 EP 4071321 B1 EP4071321 B1 EP 4071321B1 EP 21167213 A EP21167213 A EP 21167213A EP 4071321 B1 EP4071321 B1 EP 4071321B1
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Prior art keywords
laminate
concrete
corrugated
clamping unit
anchoring
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EP21167213.4A
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German (de)
English (en)
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EP4071321C0 (fr
EP4071321A1 (fr
Inventor
Justas Slaitas
Juozas Valivonis
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Vilniaus Gedimino Technikos Universitetas
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Vilniaus Gedimino Technikos Universitetas
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    • E—FIXED CONSTRUCTIONS
    • E04—BUILDING
    • E04G—SCAFFOLDING; FORMS; SHUTTERING; BUILDING IMPLEMENTS OR AIDS, OR THEIR USE; HANDLING BUILDING MATERIALS ON THE SITE; REPAIRING, BREAKING-UP OR OTHER WORK ON EXISTING BUILDINGS
    • E04G23/00—Working measures on existing buildings
    • E04G23/02—Repairing, e.g. filling cracks; Restoring; Altering; Enlarging
    • E04G23/0218—Increasing or restoring the load-bearing capacity of building construction elements
    • E—FIXED CONSTRUCTIONS
    • E04—BUILDING
    • E04C—STRUCTURAL ELEMENTS; BUILDING MATERIALS
    • E04C5/00—Reinforcing elements, e.g. for concrete; Auxiliary elements therefor
    • E04C5/08—Members specially adapted to be used in prestressed constructions
    • E04C5/12—Anchoring devices
    • E—FIXED CONSTRUCTIONS
    • E04—BUILDING
    • E04C—STRUCTURAL ELEMENTS; BUILDING MATERIALS
    • E04C5/00—Reinforcing elements, e.g. for concrete; Auxiliary elements therefor
    • E04C5/08—Members specially adapted to be used in prestressed constructions
    • E04C5/12—Anchoring devices
    • E04C5/127—The tensile members being made of fiber reinforced plastics
    • E—FIXED CONSTRUCTIONS
    • E04—BUILDING
    • E04G—SCAFFOLDING; FORMS; SHUTTERING; BUILDING IMPLEMENTS OR AIDS, OR THEIR USE; HANDLING BUILDING MATERIALS ON THE SITE; REPAIRING, BREAKING-UP OR OTHER WORK ON EXISTING BUILDINGS
    • E04G23/00—Working measures on existing buildings
    • E04G23/02—Repairing, e.g. filling cracks; Restoring; Altering; Enlarging
    • E04G23/0218—Increasing or restoring the load-bearing capacity of building construction elements
    • E04G2023/0251—Increasing or restoring the load-bearing capacity of building construction elements by using fiber reinforced plastic elements
    • E04G2023/0255—Increasing or restoring the load-bearing capacity of building construction elements by using fiber reinforced plastic elements whereby the fiber reinforced plastic elements are stressed
    • E04G2023/0259—Devices specifically adapted to stress the fiber reinforced plastic elements
    • E—FIXED CONSTRUCTIONS
    • E04—BUILDING
    • E04G—SCAFFOLDING; FORMS; SHUTTERING; BUILDING IMPLEMENTS OR AIDS, OR THEIR USE; HANDLING BUILDING MATERIALS ON THE SITE; REPAIRING, BREAKING-UP OR OTHER WORK ON EXISTING BUILDINGS
    • E04G23/00—Working measures on existing buildings
    • E04G23/02—Repairing, e.g. filling cracks; Restoring; Altering; Enlarging
    • E04G23/0218—Increasing or restoring the load-bearing capacity of building construction elements
    • E04G2023/0251—Increasing or restoring the load-bearing capacity of building construction elements by using fiber reinforced plastic elements
    • E04G2023/0262—Devices specifically adapted for anchoring the fiber reinforced plastic elements, e.g. to avoid peeling off

Definitions

  • This invention relates to the field of structural and material engineering and can be used for reinforcing the existing structural elements. More specifically, it discloses reinforcing means and a method for retrofitting concrete structures with externally bonded pre-stressed fibre-reinforced-polymer laminates.
  • Fibre-reinforced-polymers due to their corrosion resistance and high strength-to-weight ratio, have established themselves in the construction market as an appropriate material for retrofitting concrete structures, thus replacing other materials for this use, such as concrete jackets and steel plates. Fibre-reinforced polymers are expensive high strength materials.
  • the pre-stressing of FRP reinforcements is a solution for using the full potential of these high tensile strength materials. Other benefits of using the pre-stressed FRPs are reduced deflection, control of cracks, improved cracking and yield loads of the retrofitted structures.
  • the main problem of pre-stressing FRP materials is to have a reliable anchorage and clamping system to prevent or minimize slipping of the contacting surfaces of the concrete structure and FRP reinforcement and prevent debonding the FRP reinforcement from the concrete structure.
  • Chinese patent CN208578344U provides a clamping piece and hinge-type anchor device for fibre reinforced composite (FRP) panel.
  • the front end of its clamping piece type plush copper anchor is the curved surface to the evagination, and the middle part of a side of preceding spill anchoring block, spill sliding block is the curved surface to the indent, and the concave curved surface of the outer convex surface of plush copper anchor and preceding spill anchoring block and spill sliding block mates each other and constitutes the face contact and form the hinge connection.
  • the main disadvantage of this system that it is not bonded to the surface of concrete and holds only on the anchors that is quite risky and can end up with an accident if slipping would occur between the contacting surfaces of FRP panel and the anchors.
  • the clamping unit is in tension while using this method central alignment of the laminate is very important, even small eccentricities can cause longitudinal cracks in the FRP laminate with following tensile failure.
  • the anchors are made of copper, which makes the whole system much more expensive as the price of copper is approximately 13 times higher than steel.
  • Another Chinese patent application CN104895251A provides a wraparound type waveform anchor for fibre sheets and pre-tensioning method thereof.
  • the method comprises that both ends of the FRP sheet are clamped and fixedly anchored through the wraparound type waveform anchor and one end of the wraparound type waveform anchor is pulled so as to achieve the longitudinal tension of the FRP sheet.
  • the main disadvantage of this and similar systems they could be used only for FRP sheets as FRP laminate would break while trying to clamp it with a curved/wavy surface. Besides, it also has similar disadvantages to the above-described system.
  • One more Chinese patent application CN1699710A provides a pre-stressed fibre-reinforced plastic plate anchoring device and tensioning tow knee coordinated therewith.
  • the main idea of this invention is to use a wedge type clamping unit in a tension frame. Disadvantages: a tension frame takes a lot of space and can be difficult to use on a site for strengthening. Also, other disadvantages of the above-mentioned systems are valid, only the current system has a higher risk of critical eccentricities due to the absence of the hinge element.
  • European patent application EP2631392A1 provides a commercially available device for the application of force to tension members from fibre-reinforced plastic plates.
  • the device has a clamping element made of soft- and hard layers.
  • the clamping element comprises a structure without a wedge taper or a wedge-shaped or conical structure, where a cross-section reduction of the wedge runs against a tension direction of a tension element.
  • a sleeve has an interior shape for retaining the clamping element and for exerting clamping pressure.
  • the clamping unit is in tension, it means that the system will take place outside the end of the laminate and even small eccentricities can cause longitudinal cracks in the laminate with the following tensile failure.
  • the end of the laminate will be moved away from the support, such a reduced ratio of the laminate and concrete element lengths can lead to the end debonding failure mode, especially for shorter concrete elements.
  • this device requires additional damage to the concrete for using it in EBR strengthening systems. In real structure, longitudinal and transverse reinforcements won't let to make such a groove on a concrete surface. Without a groove for the clamping unit, the laminate will be too far from the concrete surface to bond it.
  • European patent EP2088259B1 provides a commercially available device for pre-tensioning reinforcement elements on structures.
  • the method involves producing pre-tensioning between a building and a clamping shoe attached at a reinforcement laminate-end by using a hydraulic cylinder-piston unit that is utilized in a device for tensioning. Pre-tensioning is maintained by driving a setscrew between a tensioning device and the clamping shoe. The piston unit is removed under retention of the pre-tensioning held by the screw. The tensioning device and the shoe are removed from a building after hardening of an adhesive.
  • the shoe is provided for clamping of the laminate-ends and a box-type metal body.
  • the main disadvantage is still a risk of slipping in the contacting surfaces of the reinforcement laminate and the plane of aluminum bloc clamping the laminate.
  • the present invention provides an advantageous clamping system and a method for pre-stressing of reinforcing FRP laminates.
  • the current invention discloses a pre-stressing system and method for retrofitting of reinforced concrete members with externally bonded CFRP laminates in bending, according to the independent claims 1 and 8.
  • the pre-stressing system comprises a clamping unit, a light frame for hydraulic jack and anchoring plates.
  • the clamping unit consists of tempered steel grips with a corrugated surface, which are tightened with high strength bolts in a steel frame. Usually, the result of using corrugated surface steel grips would be fractured laminate.
  • the solution of this invention is to add epoxy adhesive on both upper and lower contact surfaces of the grips and the laminate and tighten with high strength bolts in the steel frame. The result after one day of hardening is more effective clamping unit with very low slip potential.
  • Such units can be attached on both sides of the laminate one day before strengthening outside the construction site, this way strengthening time is not higher than using any other existing method.
  • the clamping unit can be attached on one side of the laminate and the other end can be anchored to a concrete member with riffled surface steel plates, epoxy adhesives must be added onto concrete-laminate, laminate-steel plate contact surfaces and the plates must be tightened to the concrete member with anchor bolts at once. Anchoring with plane surface plates would not withstand similar loads, even bonded with epoxy adhesive one day before the tensioning.
  • the main working principle of the system is that hydraulic jack in steel frame pushes the clamping unit through the hinge while the other side of the laminate is anchored.
  • the anchoring plates are added by the same principle described above between the clamping unit and the frame of hydraulic jack.
  • the applied force is transmitted from the jack into the frame through bolts and the jack can be removed.
  • the hydraulic jack is returned to the frame and a force of the same magnitude is added to the clamping unit.
  • the bolts are released and the force is slowly removed, transferring pre-stressing force into the anchors and concrete-laminate joint.
  • the improved anchors and clamping unit reduce the risk of the FRP laminate slipping in the clamping unit and the anchors and thus the failure of the concrete-laminate joint.
  • the pre-stressing system (presented in Figures 1 to 4 ) includes three main items: a clamping unit (1), a light frame for hydraulic jack (2) and anchoring plates (3).
  • the novel clamping unit (1) consists of tempered steel grips with the corrugated surface (4), which are tightened with high strength bolts (5) in the steel frame (6).
  • the shape of the grips (4) was specially made to bend the laminate (7) with a low angle, in order to get a better anchorage but not to break the laminate (7) at the same time (see Fig. 5 ).
  • the assembly process of the clamping unit (1) starts from adding epoxy adhesive (8) onto the corrugated surfaces of the grips (4) and closing the CFRP laminate (7) inside between the grips (4) (see Fig. 6 ).
  • the grips (4) with the laminate (7) and epoxy adhesive (8) inside are tightened in a steel frame (6) with high strength bolts (5) (see Fig. 7 ).
  • the light steel frame (2) is mounted onto a concrete surface with anchor bolts (9), or with threaded rods (10) and additional steel plates (11) in case of smaller beams ( Fig. 1 to 4 ).
  • the purpose of this frame is to hold hydraulic jack (12), serve as a support to it and take over the pre-stressing force while the adhesive hardens.
  • the third component of the pre-stressing system is the anchoring plates (3) with the corrugated surface for additional anchoring the laminate (7) to concrete element (22) (presented in Fig. 8 ). If the clamping unit (1) is assembled on the construction site one day or more before strengthening, then the laminate (7) with the clamping unit (1) on one end can be mounted to the concrete beam/slab (22), while bonding another end to the concrete beam/slab (22) is done with anchoring plates (3).
  • the clamping unit (1) and anchoring plates (3) are fully operational after one day of hardening of the epoxy adhesive (8).
  • the third component of the pre-stressing system is the anchoring plates (3) with the corrugated surface for additional anchoring the laminate (7) to concrete element (22) (presented in Fig. 8 ). If the clamping unit (1) is assembled on the construction site one day or more before strengthening, then the laminate (7) with the clamping unit (1) on one end can be mounted to the concrete beam/slab (22), while bonding another end to the concrete beam/slab (22) is done with anchoring plates (3).
  • rollers (18) can be removed from the clamping unit (1) and wider rollers (20) can be added from the other side of the beam and pressed with the steel plates (11) (see Fig. 3 ). This way rollers get support and the bending moment acting on them is removed.
  • the pre-stressing level of the FRP laminate (7) should be additionally controlled with strain gauges, not shown in the drawings, but still electromechanical indicators (LVDT's) with a sensor base of 25 mm are recommended for measuring the elongation of the laminate on the intermediate section of the element (22). If the concrete element (22) is not cracked, then the measurement base should not make any difference, but if the strengthened member (22) is cracked, then the strain gauge should be mounted on the most widely opened crack with the recommended measurement base of 50 mm. Also, depending on the length of the laminate (7), for better performance, it is advisable to add additional anchoring plates (3) on intermediate sections, not only on the ends of the laminate (7).
  • LVDT's electromechanical indicators
  • the prototype of the pre-stressing system was made and tested on the series of reinforced concrete beams on courtesy of Vilnius Gediminas Technical University. Eighteen full-scale beams were cast and tested at the local laboratory. Half of them were strengthened under external load action (a common situation in practice). Pre-stressing force varied from 20 % to 75 % of a nominal load-carrying capacity of the laminate (7), i.e. the force transmitted to the tensioning system varied from 30 kN to 125 kN. Dimensions of the beams and reinforcements are presented in Fig.

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  • Engineering & Computer Science (AREA)
  • Architecture (AREA)
  • Civil Engineering (AREA)
  • Structural Engineering (AREA)
  • Chemical & Material Sciences (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Electrochemistry (AREA)
  • Mechanical Engineering (AREA)
  • Working Measures On Existing Buildindgs (AREA)

Claims (11)

  1. Système de mise en précontrainte permettant de mettre à niveau des éléments en béton armé par flexion avec des stratifiés de polymère renforcé de fibres (FRP), collés en externe, le système comprenant au moins
    - une unité de blocage (1),
    - une ossature légère avec un vérin hydraulique (2),
    - des plaques d'ancrage (3), et
    - un stratifié de polymère renforcé de fibres, FRP, à coller en externe aux éléments en béton, avec des parties de surface,
    caractérisé en ce que
    • l'unité de blocage (1) comprend des griffes en acier trempé avec des surfaces ondulées (4) et un adhésif époxyde (8) adapté pour couvrir les surfaces de contact à la fois supérieures et inférieures des griffes (4), et en ce que les parties de surface du stratifié FRP (7) peuvent être bloquées par lesdites griffes (4), et
    • les plaques d'ancrage (3) comprennent une surface ondulée et un adhésif époxyde adapté pour couvrir la surface ondulée pour saisir les parties de surface du stratifié FRP (7) qui sont ancrées dans l'élément en béton en cours d'utilisation.
  2. Système selon la revendication 1, dans lequel les surfaces de contact des griffes en acier trempé (4) de l'unité de blocage (1) sont ondulées avec des pics.
  3. Système selon la revendication 1, dans lequel la surface de contact des plaques d'ancrage (3) est ondulée avec des creux linéaires.
  4. Système selon la revendication 1, caractérisé en ce que l'unité de blocage (1) est serrée avec des boulons à haute résistance (5) dans une ossature en acier (6).
  5. Système selon la revendication 1, caractérisé en ce que la forme des griffes (4) est réalisée pour faire fléchir le stratifié FRP (7) selon un angle de 0 à 10 degrés afin d'obtenir un meilleur ancrage.
  6. Système selon la revendication 5, caractérisé en ce que l'angle de flexion du stratifié FRP (7) est suffisamment faible pour ne pas briser le stratifié FRP (7) pendant la mise en précontrainte.
  7. Système selon l'une quelconque des revendications 1 à 6, caractérisé en ce que les plaques d'ancrage (3) sont des parties permanentes et l'ossature légère pour le vérin hydraulique (2), des rails en acier (13) pour les unités de blocage sont des parties temporaires, les parties permanentes et temporaires pouvant être serrées contre la poutre/dalle en béton (22) avec des boulons d'ancrage (9) ou serrées par des tiges filetées (10) et des plaques en acier supplémentaires (11) du système, au cas où le système serait appliqué à des éléments en béton sous la forme de poutres plus petites.
  8. Procédé permettant de renforcer un élément en béton par des stratifiés de polymère renforcé de fibres (FRP) précontraints, collés en externe, comprenant au moins les étapes consistant à :
    (a) bloquer un stratifié FRP (7) avec des surfaces par une unité de blocage (1) ayant des griffes en acier trempé avec des surfaces ondulées (4) de sorte que les surfaces du stratifié FRP (7) sont bloquées par lesdites surfaces ondulées des griffes en acier (4), alors qu'une autre extrémité du stratifié FRP (7) est ancrée dans l'élément en béton (22) avec une plaque d'ancrage (3) ayant une surface de contact ondulée.
    (b) monter l'unité de blocage (1) ensemble avec une autre plaque d'ancrage (3) ayant une surface de contact ondulée, et une ossature en acier légère avec un vérin hydraulique (2) sur l'élément en béton (22) en cours de renforcement ;
    (c) précontraindre le stratifié FRP (7) avec le vérin hydraulique (2),
    (d) fixer le stratifié FRP (7) précontraint à la structure en béton (22) en serrant l'autre plaque d'ancrage (3) montée à l'étape (b),
    dans lequel, à l'étape (a)
    - avant le blocage, les surfaces ondulées des griffes en acier trempé (4) et les surfaces du stratifié FRP (7) à bloquer par lesdites griffes (4) sont recouvertes d'un adhésif époxyde (8) ;
    - l'unité de blocage (1) est serrée avec des boulons à haute résistance (5) dans l'ossature en acier légère (6) ;
    - après le blocage, on laisse reposer le stratifié FRP (7) et l'unité de blocage (1) pendant une journée de durcissement de l'adhésif époxyde (8), et
    - la surface de contact ondulée de la plaque d'ancrage (3) à l'autre extrémité du stratifié (7), avant l'ancrage, est recouverte d'un adhésif époxyde, et après l'ancrage du stratifié FRP (7), on laisse reposer cette plaque d'ancrage (3) pour le durcissement de l'adhésif époxyde (8),
    et à l'étape (b),
    - la surface de contact ondulée de l'autre plaque d'ancrage (3) est également recouverte d'un adhésif époxyde (8) .
  9. Procédé selon la revendication 8, caractérisé en ce qu'à l'étape (b), des rails en acier (13) pour l'unité de blocage et l'ossature légère pour le vérin hydraulique (2) sont des parties temporaires et sont serrées contre l'élément en béton (22), mais l'unité de blocage (1) elle-même et l'autre plaque d'ancrage (3) ne sont pas serrées contre l'élément en béton (22).
  10. Procédé selon la revendication 8, caractérisé en ce que l'étape (c) utilise des rouleaux (18) et des rouleaux (20) plus larges de façon à réduire les pertes par frottement et par précontrainte, l'élément en béton (22) se présentant sous la forme d'une poutre plus petite.
  11. Procédé selon la revendication 9, caractérisé en ce que l'étape (d) comprend le serrage des plaques d'ancrage (3) contre l'élément en béton (22) avec des boulons d'ancrage (9), ou contre l'élément en béton (22) sous la forme d'une poutre plus petite, en serrant avec des tiges filetées (10) et des plaques en acier supplémentaires (11) après qu'une force de précontrainte théorique est atteinte, de sorte que l'étape (d) comprend en outre un durcissement total de l'adhésif époxyde sur l'élément en béton (22), le stratifié FRP (7) et les autres plaques d'ancrage (3) ajoutées à l'étape (b), et ensuite les parties temporaires sont retirées.
EP21167213.4A 2021-04-07 2021-04-07 Système et procédé pour structures de renforcement avec stratifiés de polymère renforcé de fibres pré-contraints Active EP4071321B1 (fr)

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Publication number Priority date Publication date Assignee Title
JP4004616B2 (ja) * 1997-12-24 2007-11-07 智深 呉 繊維材緊張によるコンクリート部材の補強方法
KR100660029B1 (ko) * 2004-12-01 2006-12-20 한국건설기술연구원 프리스트레스트가 도입된 섬유보강복합체를 이용한 구조물빔 전단보강장치
CN1699710A (zh) 2005-04-30 2005-11-23 中材科技股份有限公司 预应力纤维增强塑料板材锚固装置及配套使用的张拉推架
CH700733B1 (de) * 2008-01-28 2010-10-15 Josef Scherer Mechanisches Endverankerungselement für Verstärkungslaminate an Bauwerken.
CH701655B1 (de) 2008-02-08 2011-02-28 Josef Scherer Verfahren und Vorrichtung zum Vorspannen von Verstärkungslaminaten an Bauwerken.
CN201778500U (zh) * 2010-08-16 2011-03-30 合肥工业大学 预张拉碳纤维板加固混凝土梁板的装置
EP2631392A1 (fr) 2012-02-21 2013-08-28 Sika Technology AG Dispositif d'introduction de force dans des éléments de traction à partir de lamelles de bandes plates en matière synthétique renforcées en fibres
CN104895251A (zh) 2014-03-04 2015-09-09 五邑大学 用于纤维片材的绕回式波形锚及其预张拉方法
CN208578344U (zh) 2018-05-02 2019-03-05 山西省交通科学研究院 一种纤维增强复合材料板材的夹片型铰式锚装置

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SLAITAS JUSTAS ET AL: "Anchoring Issues of CFRP Laminates to Concrete Members", POLYMERS, vol. 14, no. 12, 14 June 2022 (2022-06-14), CH, pages 2338, XP093040616, ISSN: 2073-4360, DOI: 10.3390/polym14122338 *

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EP4071321A1 (fr) 2022-10-12

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