EP4071321A1 - Dispositif et procédé pour structures de renforcement avec stratifiés de polymère renforcé de fibres pré-contraints - Google Patents

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

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Publication number
EP4071321A1
EP4071321A1 EP21167213.4A EP21167213A EP4071321A1 EP 4071321 A1 EP4071321 A1 EP 4071321A1 EP 21167213 A EP21167213 A EP 21167213A EP 4071321 A1 EP4071321 A1 EP 4071321A1
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EP
European Patent Office
Prior art keywords
laminate
clamping unit
grips
frp
steel
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Pending
Application number
EP21167213.4A
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German (de)
English (en)
Inventor
Justas Slaitas
Juozas Valivonis
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Vilniaus Gedimino Technikos Universitetas
Original Assignee
Vilniaus Gedimino Technikos Universitetas
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Vilniaus Gedimino Technikos Universitetas filed Critical Vilniaus Gedimino Technikos Universitetas
Priority to EP21167213.4A priority Critical patent/EP4071321A1/fr
Publication of EP4071321A1 publication Critical patent/EP4071321A1/fr
Pending legal-status Critical Current

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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 device and a method for pre-stressing of reinforcing FRP laminates.
  • the current invention discloses a pre-stressing device for retrofitting of reinforced concrete members with externally bonded CFRP laminates in bending.
  • the pre-stressing system includes a clamping unit, a light frame for hydraulic jack and anchoring plates.
  • the novel clamping unit consists of tempered steel grips with a corrugated surface, which are tightened with high strength bolts in a steel frame.
  • plane surfaces were used in all pre-stressing systems mentioned in the previous section (patent No. CN208578344U provides a wavy shape of the clamping unit to bend the FRP material, what is unacceptable for laminates, but the surface itself is still plane).
  • the catch 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.
  • 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. If one day does not make any difference, the clamping unit can be attached on one side of the laminate and the other end can be anchored to concrete 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 concrete with anchor bolts at once. Anchoring with plane surface plates as proposed in the prior art would not withstand similar loads, even bonded with epoxy adhesive one day before the tensioning.
  • the current invention provides retrofitting solutions not only for concrete slabs and wide beams as it does previously mentioned systems but also for smaller beams by using the steel clamps instead of direct fixing to concrete.
  • 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. This way precise central alignment of the laminate is far less important as in tensile systems (e.g. patents No. CN208578344U , CN104895251A , CN1699710A , EP2631392A1 ).
  • 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 process is similar to the one provided in European patent No. EP2088259A1 , but 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 frame of the clamping unit has attached rollers that can move through rail holding the clamping unit attached to the ceiling, this way the effect of friction between surfaces is lower than it is in European patent No. EP2088259B1 . In the case of smaller beams, the rollers can be added on the other side of the beam.
  • 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).
  • First step the surface of the concrete beam/slab (22) is grinded and cleaned with the cleaner.
  • Second step the laminate (7) is cleaned the same way as the concrete object (22), the epoxy adhesive (8) is added onto the corrugated surfaces of the grips (4) and the CFRP laminate (7) is closed 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 ).
  • Twelfth step the tensile force is released from the hydraulic jack (12), which now can be removed.
  • 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.
  • f cm - mean compressive strength of concrete cylinders f y.s1 - yield strength of tensile steel reinforcements; E s1 - modulus of elasticity of tensile steel reinforcements; f y.s2 - yield strength of compressive steel reinforcements; E s2 - modulus of elasticity of compressive steel reinforcements; f fu - tensile strength of CFRP laminate; E f - modulus of elasticity of CFRP laminate; P - pre-stressing force.

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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)
EP21167213.4A 2021-04-07 2021-04-07 Dispositif et procédé pour structures de renforcement avec stratifiés de polymère renforcé de fibres pré-contraints Pending EP4071321A1 (fr)

Priority Applications (1)

Application Number Priority Date Filing Date Title
EP21167213.4A EP4071321A1 (fr) 2021-04-07 2021-04-07 Dispositif et procédé pour structures de renforcement avec stratifiés de polymère renforcé de fibres pré-contraints

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Application Number Priority Date Filing Date Title
EP21167213.4A EP4071321A1 (fr) 2021-04-07 2021-04-07 Dispositif et procédé pour structures de renforcement avec stratifiés de polymère renforcé de fibres pré-contraints

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EP4071321A1 true EP4071321A1 (fr) 2022-10-12

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Citations (9)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
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
KR20060060935A (ko) * 2004-12-01 2006-06-07 한국건설기술연구원 프리스트레스트가 도입된 섬유보강복합체를 이용한 구조물빔 전단보강장치
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
EP2083133A2 (fr) * 2008-01-28 2009-07-29 S&P Clever Reinforcement Company AG Elément d'ancrage mécanique d'extrémité pour laminés de renforcement sur des constructions
EP2088259A1 (fr) 2008-02-08 2009-08-12 S&P Clever Reinforcement Company AG Procédé et dispositif de pré-tension d'éléments de renforcement sur des constructions
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

Patent Citations (10)

* Cited by examiner, † Cited by third party
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
KR20060060935A (ko) * 2004-12-01 2006-06-07 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
EP2083133A2 (fr) * 2008-01-28 2009-07-29 S&P Clever Reinforcement Company AG Elément d'ancrage mécanique d'extrémité pour laminés de renforcement sur des constructions
EP2088259A1 (fr) 2008-02-08 2009-08-12 S&P Clever Reinforcement Company AG Procédé et dispositif de pré-tension d'éléments de renforcement sur des constructions
EP2088259B1 (fr) 2008-02-08 2011-10-12 Josef Scherer Dispositif de pré-tension d'éléments de renforcement sur des constructions
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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