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WO2003053679A1 - Tissu structurel hybride ductile - Google Patents

Tissu structurel hybride ductile Download PDF

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Publication number
WO2003053679A1
WO2003053679A1 PCT/US2002/037608 US0237608W WO03053679A1 WO 2003053679 A1 WO2003053679 A1 WO 2003053679A1 US 0237608 W US0237608 W US 0237608W WO 03053679 A1 WO03053679 A1 WO 03053679A1
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WO
WIPO (PCT)
Prior art keywords
fibers
fabric
fiber
diagonal
ultimate strain
Prior art date
Application number
PCT/US2002/037608
Other languages
English (en)
Inventor
Nabil F. Grace
Wael F. Ragheb
George Abdel-Sayed
Original Assignee
Lawrence Technological University
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
Priority claimed from US10/164,737 external-priority patent/US6790518B2/en
Application filed by Lawrence Technological University filed Critical Lawrence Technological University
Priority to AU2002346493A priority Critical patent/AU2002346493A1/en
Publication of WO2003053679A1 publication Critical patent/WO2003053679A1/fr

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Classifications

    • E—FIXED CONSTRUCTIONS
    • E04—BUILDING
    • E04C—STRUCTURAL ELEMENTS; BUILDING MATERIALS
    • E04C5/00—Reinforcing elements, e.g. for concrete; Auxiliary elements therefor
    • E04C5/07—Reinforcing elements of material other than metal, e.g. of glass, of plastics, or not exclusively made of metal
    • D—TEXTILES; PAPER
    • D04—BRAIDING; LACE-MAKING; KNITTING; TRIMMINGS; NON-WOVEN FABRICS
    • D04C—BRAIDING OR MANUFACTURE OF LACE, INCLUDING BOBBIN-NET OR CARBONISED LACE; BRAIDING MACHINES; BRAID; LACE
    • D04C1/00—Braid or lace, e.g. pillow-lace; Processes for the manufacture thereof
    • D04C1/02—Braid or lace, e.g. pillow-lace; Processes for the manufacture thereof made from particular materials
    • 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
    • D—TEXTILES; PAPER
    • D10—INDEXING SCHEME ASSOCIATED WITH SUBLASSES OF SECTION D, RELATING TO TEXTILES
    • D10B—INDEXING SCHEME ASSOCIATED WITH SUBLASSES OF SECTION D, RELATING TO TEXTILES
    • D10B2403/00—Details of fabric structure established in the fabric forming process
    • D10B2403/02—Cross-sectional features
    • D10B2403/024—Fabric incorporating additional compounds
    • D10B2403/0241—Fabric incorporating additional compounds enhancing mechanical properties
    • D10B2403/02411—Fabric incorporating additional compounds enhancing mechanical properties with a single array of unbent yarn, e.g. unidirectional reinforcement fabrics
    • D—TEXTILES; PAPER
    • D10—INDEXING SCHEME ASSOCIATED WITH SUBLASSES OF SECTION D, RELATING TO TEXTILES
    • D10B—INDEXING SCHEME ASSOCIATED WITH SUBLASSES OF SECTION D, RELATING TO TEXTILES
    • D10B2505/00—Industrial
    • D10B2505/02—Reinforcing materials; Prepregs
    • 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

Definitions

  • High strength composite fibers have been used for a variety of applications.
  • FRP externally bonded fiber reinforced polymer
  • Steel-reinforced concrete beams strengthened with FRP strengthening systems show higher ultimate load strengths compared to non-strengthened concrete beams.
  • available FRP strengthening systems suffer from a variety of disadvantages and drawbacks including lack of ductility and high orthotropic characteristics.
  • Loss of beam ductility is partially attributable to the brittle nature of fibers used in FRP strengthening systems. Fibers commonly used in FRP strengthening systems, such as carbon fibers, glass fibers, or aramid fibers while exhibiting higher ultimate tensile strengths than steel reinforcement, tend to fail catastrophically and without visual warning. Visual indicators of structural weaknesses are desirable as they permit the opportunity for remedial actions prior to failure. Accordingly, it would be desirable to realize the strengthening benefits of FRP systems without sacrificing beam ductility. As to the timing of the load gains from FRP strengthening, it is noted that FRP strengthening materials behave differently from steel. Although fibers used in FRP materials have high strengths, they generally stretch to relatively high strain values before providing their full strength.
  • Steel also has a relatively low yield strain value (on the order of 0.2 % for Grade 60 steel) compared to the yield strain of commonly used FRP fibers (on the order of 1.4-1.7% for Carbon fibers and 2-3 % for glass fibers). Accordingly, the degrees of contribution of the reinforcing steel and the strengthening FRP materials differ with the magnitude that the strengthened element deforms, with FRP contributions being most significant after the yield strain of steel. Stated differently, the steel reinforcement commonly yields before the FRP provides any significant strengthening.
  • FRP fabrics, sheets, and strips also have high orthotropic characteristics. That is, the fabrics provide strengthening only in the direction of fiber orientation.
  • the orthotropic characteristic of FRP fabrics limit their usefulness in applications subjected to multi-directional loads such as simultaneous flexure and shear strengthening of structural components.
  • a ductile structural fabric such as an FRP fabric or sheet.
  • the fabric also preferably exhibits a low strain yield so that the fabric effectively enhances the strength of the beam prior to yielding of the steel reinforcement.
  • a ductile structural fabric which can be used for strengthening in more than one direction. In other words, the fabric is desired to have reduced orthotropic characteristics.
  • the present invention is directed to a structural fabric having a first fiber with a first ultimate strain, a second fiber with a second ultimate strain greater than the first ultimate strain, the first and second fibers being in the same plane.
  • the invention is further directed to a structural fabric having a plurality of axial fibers and a plurality of first diagonal fibers braided with the axial fibers and oriented at a first braid angle relative thereto.
  • the axial fibers include first and second fibers each with an ultimate strain. The ultimate strain of the second fiber again being greater than the ultimate strain of the first fiber.
  • the invention is directed to a concrete beam strengthened with the structural fibers of the present invention.
  • FIG. 1 is a cross-sectional view of a reinforced concrete beam with an FRP fabric in accordance with the present invention
  • FIG. 2 is a plan view of a fabric having a plurality of axial yarns in accordance with the present invention
  • FIG. 3 is a plan view of the repeating cell of fibers in the fabric of FIG. 2 illustrating the mix of axial fibers within the fabric;
  • FIG. 4 is a graph illustrating the load versus mid-span deflection of a concrete beam strengthened with 1 mm thick uniaxial fabric along only the bottom surface of the beam
  • FIG. 5 is a graph illustrating the strain at mid-span of a concrete beam strengthened with 1 mm thick uniaxial fabric along only the bottom surface of the beam
  • FIG. 6 is a graph illustrating the load versus mid-span deflection of a concrete beam strengthened with 1.5 mm thick uniaxial fabric along only the bottom surface of the beam;
  • FIG. 7 is a graph illustrating the strain at mid-span of a concrete beam strengthened with 1.5 mm thick uniaxial fabric along only the bottom surface of the beam
  • FIG. 8 is a graph illustrating the load versus mid-span deflection of a concrete beam strengthened with 1 mm thick uniaxial fabric along both the bottom surface and extending up a portion of the side surfaces of the beam;
  • FIG. 9 is a graph illustrating the strain at mid-span of a concrete beam strengthened with 1 mm thick uniaxial fabric along both the bottom surface and extending up a portion of the side surfaces of the beam;
  • FIG. 10 is a graph illustrating the load versus mid-span deflection of a concrete beam strengthened with 1.5 mm thick uniaxial fabric along both the bottom surface and extending up a portion of the side surfaces of the beam;
  • FIG. 11 is a graph illustrating the strain at mid-span of a concrete beam strengthened with 1.5 mm thick uniaxial fabric along both the bottom surface and extending up a portion of the side surfaces of the beam;
  • FIG. 12 is a plan view of a ductile structural fabric having a plurality of axial yarns as well as a plurality of diagonal yarns in accordance with the present invention
  • FIG. 13 is a plan view of the repeating cell of fibers in the fabric of FIG. 12 illustrating the mix of axial and diagonal fibers within the fabric;
  • FIG. 14 is a graph illustrating the load versus mid-span deflection of a concrete beam strengthened with a 3.5 mm thick triaxial fabric along only the bottom surface of the beam;
  • FIG. 15 is a graph illustrating the strain at mid-span of a concrete beam strengthened with a 3.5 mm thick triaxial fabric along only the bottom surface of the beam;
  • FIG. 16 is a graph illustrating the stress-strain behavior of the uniaxial fabric and showing the energy absorption
  • FIG. 17 is a graph illustrating the axial stress-strain behavior of the triaxial fabric and showing the energy absorption.
  • the invention is generally directed to a Ductile Hybrid Fabric (DHF), such as an FRP fabric, having a plurality of fibers oriented in a predetermined repeating pattern.
  • DHF Ductile Hybrid Fabric
  • the first described embodiment of the invention relates to a uniaxial fabric wherein the fibers are positioned in a single plane and oriented parallel to one another.
  • the second embodiment is a triaxial fiber having axial fibers and diagonal fibers in two directions.
  • the fabric includes at least two fibers having different elongation characteristics embedded in a matrix.
  • the type, size, proportion, and location of the individual fibers are selected to provide a high strength and ductile structural fabric specifically tailored to a particular application.
  • the fabric composition is specifically selected to contribute to the strength of the reinforced structural component before, during, and after yielding of the steel reinforcing material.
  • the fabric can be used as an energy absorbing structural component of a building or vehicle that increases the ability of the structure or vehicle to dissipate energy including impact energy resulting from terrorist weaponry.
  • the fabric can be used with a variety of injected matrices to increase the strength of buildings subject to attack, such as nuclear power plants, high-rise buildings, highway/railroad bridges, and the like.
  • the DHF can be formed in solid shapes and configurations to develop structural panels, structural components or reinforcement for vehicles and aircraft fuselages as well as critical components of military vehicles such as tracks, wheels, panels, drive shafts, and suspension systems thereby reducing the weight of such vehicles and permitting more efficient transportation, better fuel economy, and improved maneuverability.
  • the fabric can also be used as a structural component for sports goods.
  • FIG. 1 is a cross-sectional view of a representative concrete beam 8 having a structural fabric 10 according to the present invention adhered to the bottom surface of the beam.
  • the fabric 10 improves beam strength and stiffness while exhibiting ductile characteristics that provide significant energy dissipation during loading.
  • the fabric 10 is shown to have a plurality of axial yarns or fibers 12 that include at least two axial fibers 14 and 16 having different elongation characteristics.
  • a fiber's elongation characteristic refers to the strain that the fiber withstands prior to yield or ultimate failure.
  • Various fibers are referred to herein as "low elongation,” “medium elongation” and “high elongation.” These terms refer to the elongation characteristics of fibers relative to one another. Thus, low elongation fibers withstand relatively small amounts of strain prior to yielding or failure and high elongation fibers withstand greater deformation.
  • the selection of fibers having the desired elongation characteristics may be further based upon the deformation behavior of the materials of the reinforced structure (e.g., the concrete beam), the desired load transitioning between fibers 12, as well as the ultimate strength of the fabric reinforced beam.
  • the materials of the reinforced structure e.g., the concrete beam
  • the desired load transitioning between fibers 12 as well as the ultimate strength of the fabric reinforced beam.
  • the fibers are impregnated in a matrix 26, such as an epoxy resin, that bonds the fibers to one another and to the beam in a manner that ensures that all fibers elongate at the same rate.
  • a matrix 26 such as an epoxy resin
  • the matrix is injected or interspersed throughout the fabric to fill the voids between the fibers as well as to provide a uniform outer surface and an appropriate bonding surface for coupling the fabric to the beam or other material to be strengthened.
  • the matrix material is preferably selected so that its ultimate strain is greater than the ultimate strain of the highest elongation fibers in the fabric. Based upon testing performed to date, it is anticipated that an epoxy such as DER 332 resin and DEH 24 hardener (produced by The Dow Chemical Company) is suitable.
  • the epoxy should be chemically and thermally compatible with the selected fibers. Notwithstanding the suitability of the identified epoxy, it should be appreciated that other matrix materials may be used. For example, a high-strength cement slurry may be particularly suitable for certain applications, including fabrics used to reinforce outer surfaces of a building to increase the building's impact resistance. The matrix preferably provides further benefits of thermal resistance and preventing spalling of strengthened concrete structural components. Those skilled in the art will appreciate that a variety of other polymeric and non-polymer matrix materials may be used without departing from the scope of the invention defined by the appended claims.
  • FIG. 3 is a plan view of a portion of the uniaxial fabric 10 of FIG. 2 illustrating a repeating cell of axial fibers 14 and 16 within the uniaxial fabric 10.
  • the desirable strength and ductility characteristics of the fabric and reinforced beam are achieved by incorporating at least two fibers having different elongation characteristics into the fabric. More particularly, the fabric includes one axial fiber 14 having low elongation characteristics and another axial fiber 16 having high elongation characteristics. The type, size, proportion, and location of the fibers 14 and 16 are selected to provide a desired stress - strain response as the uniaxial fabric 10 is loaded in tension.
  • the uniaxial fabric 10 when the uniaxial fabric 10 is loaded in tension, the low elongation fibers 14 fail before the high elongation fibers 16 allowing a strain relaxation or, in other words, an increase in strain without an increase in load.
  • the resulting ductile behavior of the fabric assists in energy dissipation and further provides visual or other indicators of dimensional instability. For example, the fabric commonly generates an audible "clicking" as the fibers fail.
  • the remaining high elongation fibers 16 are proportioned to sustain the total load up to failure.
  • the ultimate strain of the low elongation fibers 14 presents the value of the yield strain of the uniaxial fabric 10 while the ultimate strain of the high elongation fibers 16 presents the value of ultimate fabric strain.
  • the load corresponding to the failure of the low elongation fibers 14 presents the yield load value of the fabric and the maximum load carried by the high elongation fibers 16 is the ultimate load value.
  • the low elongation fibers exhibit an ultimate strain equal to or slightly greater than the yield strain of the reinforcing steel (e.g., about 0.2% for Grade 60 steel).
  • the low elongation fibers contribute significantly to the yield strength of the fabric reinforced beam.
  • Ultra high modulus carbon fibers with a failure strain of approximately 0.35% have been found to be suitable low elongation fibers for such applications.
  • the high elongation fibers 16 it is preferred that these fibers exhibit a significantly higher ultimate strain to produce a high ductility index (the ratio between deformation at failure and deformation at first yield).
  • E-glass fibers, such as those available from PPG industries(Hybon 2022) and having 2.1% ultimate strain have been found to be suitable for such applications.
  • the plurality of axial yams 12 even more preferably include three axial fibers 14, 16, and 18 each having different elongation characteristics.
  • the three axial fibers include the above-described low elongation fibers 14 and high elongation fibers 16 as well as medium elongation fibers 18.
  • the medium elongation fibers 18 are high modulus carbon fibers having a failure strain of about 0.8% to about 1.0% (such as Carbon #2 or Carbon #3).
  • the medium elongation fibers 18 minimize the load drop during the strain relaxation occurring after failure of the low elongation fibers 14 thereby gradually transitioning the load from the low elongation fibers 14 to the high elongation fibers 16 and enhancing the energy dissipation and ductility of the fabric.
  • additional axial fibers having different elongation characteristics may be included in the fabric to further graduate the transition of load between successively breaking fibers.
  • a triaxial fabric 40 is described below to include a fiber arrangement in three directions and comprised of fibers whose type, size, proportion, and location are similarly selected based upon performance criteria. While a variety of factors may impact the suitability of a particular fiber material, factors of particular concern include the modulus of elasticity and failure strain of each fiber. These performance characteristics impact the overall ductility and energy dissipation characteristics of the fabric.
  • Table 1 illustrates the preferred fiber material for the uniaxial and triaxial fabric described herein with the Carbon #2 medium elongation fibers being used in the three fiber uniaxial fabric and the Carbon #3 medium elongation fibers being used in the triaxial fabric.
  • the modulus of elasticity and tensile strength values shown in Table 1 are composite properties based upon a 60% fiber volume fraction.
  • the magnitude of the absorbed energy is dictated by the inelastic deformation of the fabric characterized by the strain relaxation occurring when fibers fail.
  • the uniaxial fabric exhibited an energy absorption ratio (the ratio between the absorbed energy to the total energy) of approximately 32% before failure, while the triaxial fabric exhibited an energy absorption ratio of approximately 42%.
  • While representative low, medium, and high elongation fibers are generally described above, it should be appreciated that the type, size, proportion, and location of the fibers should be considered in formulating the specific configuration of the fabric 10.
  • the types of fibers while ultra-high modulus carbon fibers, high modulus carbon fibers, and E-glass fibers are generally suitable for the low, medium, and high elongation fibers, respectively, the selection of the particular fibers for an application should consider tensile strength, elongation, modulus of elasticity, creep rupture, and shear strength as well as cost and manufacturability.
  • the factors of particular interest generally are the failure strain and modulus of elasticity of the respective fibers and the impact of these factors on the ductility and energy dissipation capabilities of the fabric. Based upon this description, those skilled in the art will be able to select suitable fibers from those commonly available in the art including ultra high modulus carbon fibers, high modulus carbon fibers, regular modulus carbon fibers, S-glass fibers, aramid fibers, and nylon fibers.
  • fibers having different elongation characteristics are preferably distributed along the fabric to provide a generally uniform distribution of the different fiber types.
  • the number of each type of fiber should be selected to ensure that the respective fibers fail at the desired loadings.
  • the repeating cell of the fabric 10 illustrated in FIGS. 2 and 3 include eight individual fibers. The fibers are positioned, from left to right, with a single low elongation fiber at position 5, medium elongation fibers at positions 3 and 7, and high elongation fibers at positions 1, 2, 4, 6, and 8.
  • the low elongation fibers 14 are made from ultra high modulus carbon fibers, the medium elongation fibers 18 from high modulus carbon fibers, and the high elongation fibers 16 are made from E-glass fibers.
  • the spacing between fibers 14, 16, and 18 is approximately 0.125 inches.
  • This configuration was developed using the above described preferred fiber materials in order to strengthen a steel reinforced concrete beam as described in the following test results. The testing of the fabric reinforced concrete beams indicate improved yield strengths, ultimate strengths, and ductile behavior not previously achieved with FRP strengthening systems. It should be appreciated that the specific fabric configuration as well as the test results are provided for illustration and should not be interpreted to unduly limit the scope of the present invention.
  • reinforced concrete beams 8 (FIG. 1) having cross sectional dimensions of 152 mm x 254 mm (6 in. x 10 in.) and lengths of 2744 mm (108 in.).
  • the flexure reinforcement of the beams consisted of two #5 (16 mm) tension bars 20 and two #3 (9.5 mm) compression bars 22. To avoid shear failure, the beams were over-reinforced for shear with #3 (9.5 mm) closed stirrups 24 spaced at 102 mm (4.0 in.).
  • Grade 60 steel having a yield strength of 415 MPa (60,000 psi) was used for all reinforcing steel.
  • the compressive strength of the unreinforced concrete at the time the beams were tested was 55.2 MPa (8,000 psi).
  • the first test sample of uniaxial fabric had a thickness of 1.0 mm (0.04 in.) and the second test sample of uniaxial fabric had a thickness of 1.5 mm (0.06 in.).
  • the different fabric thicknesses result from the use of different yarn or fiber sizes.
  • the matrix material 26 was a DER 332 + DEH 24 hardener epoxy resin that impregnated the uniaxial fabric 10 and adhered the fabric to the appropriate surface(s) of the concrete beams.
  • the epoxy had an ultimate strain of 4.4 % to insure that the epoxy would not fail before failure of the axial fibers 14, 16, and 18.
  • the bottom and side surfaces of the beams were sandblasted to roughen the surfaces and then cleaned with acetone to remove any dirt.
  • Two beams were formed with a cross-sectional shape having squared corners.
  • the uniaxial fabric 10 was adhered only to the bottom surface of these beams as shown in FIG. 1.
  • Two other beams (not shown) were formed with rounded corners, having 25 mm (1 in.) radius, in order to facilitate the adherence of uniaxial fabric 10 to both the bottom surface as well as extending 152 mm (6 in.) up each side surface of the beams without producing stress concentrations.
  • the uniaxial fabric 10 was extended along 2.24 m (88 in) of the length of the beams.
  • FIGS. 4-7 illustrate test results for a simple beam under two-point loading and strengthened with the uniaxial fabric 10 along only the bottom surface of the beams.
  • FIG. 4 shows the load versus mid-span deflection response 30 for the beam strengthened with the 1 mm thick uniaxial fabric as compared to the load versus mid- span deflection response 32 for the control beam.
  • FIG. 5 illustrates the FRP strain at mid-span showing that the uniaxial fabric 10 had approximately a strain of 0.35% indicating that the beam yielded simultaneously with the steel.
  • the strengthened beam exhibited a considerable yielding plateau (ductility index is 2.33) up to failure by total rupture of the uniaxial fabric 10 at an ultimate load of 114.8 kN (25.8 kips).
  • FIG. 6 shows the load versus mid-span deflection response 34 for the beam strengthened with 1.5 mm thick uniaxial fabric as compared to the load versus mid- span deflection response 32 for the control beam.
  • the fabric reinforced beam yielded at a load of 113.9 kN (25.6 kips), due to the simultaneous yielding of both the steel and the uniaxial fabric 10. This beam showed a considerable yielding plateau before total failure resulting from debonding of the uniaxial fabric 10 at an ultimate load of 130.8 kN (29.4 kips).
  • FIG. 7 illustrates the FRP strain at mid-span showing that although final failure was caused by the debonding of the uniaxial fabric 10, debonding occurred after achieving a reasonable ductility. A ductility index of 2.13 was experienced.
  • FIGS. 8-11 illustrate test results for control beams strengthened with uniaxial fabric 10 along both the bottom surface and extending up a portion of the side surfaces of the beams.
  • FIG. 8 shows the load versus mid-span deflection response 36 for the beam strengthened with 1 mm thick uniaxial fabric as compared to the load versus mid-span deflection response 32 for the control beam.
  • the strengthened beam yielded at a load of 113.9 kN (25.6 kips) due to the simultaneous yielding of both the steel and the uniaxial fabric 10.
  • the increase in yield load gained was 38%.
  • a yielding plateau before final failure occurred at an ultimate load of 146.4 kN (32.9 kips) due to compression failure of the concrete.
  • a ductility index of 2.25 was experienced.
  • FIG. 9 illustrates the FRP strain at mid-span showing the maximum recorded strain before beam failure was 1.2%.
  • FIG. 10 shows the load versus mid-span deflection response 38 of the beam strengthened with 1.5 mm thick uniaxial fabric as compared to the load versus mid- span deflection response 32 of the control beam.
  • FIG. 10 shows that the strengthened beam yielded at a load of 127.3 kN (28.6 kips) with an increase in yield load of 55%, due to the simultaneous yielding of both the steel and the uniaxial fabric 10.
  • This beam finally failed at an ultimate load of 162.0 kN (36.4 kips) due to compression failure of the concrete at mid-span.
  • This beam experienced a ductility index of 1.89.
  • FIG. 11 illustrates the FRP strain at mid-span showing the maximum recorded strain before beam failure was 0.74%.
  • FIG. 12 is a plan view of another embodiment of a ductile structural fabric 40 according to the present invention.
  • the fabric 40 has a plurality of axial yarns 42 as well as a plurality of diagonal yarns 44.
  • the diagonal yarns 44 are braided with the axial yarns 42 to provide a desired stress - strain response as the fabric 40 is loaded in tension in both the axial and diagonal directions.
  • the fibers forming the axial yarns 42 include at least two, and preferably at least three, different types of fibers having different elongation characteristics.
  • the illustrated embodiment again includes axial yarns 42 made from low elongation fibers 14, medium elongation fibers 18, and high elongation fibers 16 (FIG. 13).
  • the diagonal fibers 44 may also be made from a variety of materials and again preferably include at least two fibers having different elongation characteristics.
  • the diagonal fibers are made from medium elongation fibers 46 and high elongation fibers 48 which may be the same as, or different from, the medium and high elongation fibers 18 and 16 used in the axial direction.
  • the elongation ratio between axial fibers 14, 16 and 18 and between the diagonal fibers 46 and 48 within the fabric 40 are again selected to provide high stiffness before yield as well as ductility.
  • the triaxial fabric 40 is braided with the axial fibers 42 being aligned in a single plane and the diagonal fibers 44 woven in an undulated fashion above and below adjacent axial fibers.
  • the diagonal yarns 44 form a braid angle 50 (FIG. 12) that is preferably, though not necessarily, equal to forty-five degrees.
  • a forty-five degree braid angle has the benefit of orienting the diagonal yarns substantially pe ⁇ endicular to the potential shear cracks thereby enhancing the strengthening by resisting the diagonal tension due to shear.
  • the fabric provides beam shear strengthening in addition to the flexural strengthening when the fabric is installed on the beam sides.
  • a variety of braiding or weaving techniques may be used to manufacture the triaxial fabric 40. However, a 2x2 triaxial braiding technique has been found to be particularly suitable for braiding the fibers contemplated for the present invention.
  • FIG. 13 is a plan view of a portion of the triaxial fabric 40 of FIG. 12 illustrating the mix of the axial fibers 42 and the diagonal fibers 44 within the repeating cells of the triaxial fabric 40.
  • the remaining medium elongation fibers 18, high elongation fibers 16, and the diagonal yarns 44 are selected and proportioned to incrementally sustain the total load after failure of the low elongation fibers 14 in the same manner as in the uniaxial fabric 10.
  • the medium elongation fibers 18 fail allowing a second strain relaxation.
  • the amount of high elongation fibers 16 and the diagonal yarns 46 and 48 are chosen to sustain the total load up to failure.
  • the first and second strain relaxations provide considerable fabric ductility.
  • the ductile behavior is achieved in a slightly different manner.
  • the fibers fail thereby allowing a strain relaxation,
  • the remaining diagonal high elongation fibers 46 as well as the axial yarns are selected and proportioned to sustain the total load up to design failure.
  • the maximum strain values for each fiber are properly selected to fit with ductility mechanisms as well as the stiffness requirements. In selecting the diagonal medium elongation fibers 46, consideration of the undulation of the diagonal fibers should be made.
  • the undulating fibers can not sustain the same strain magnitudes as when the fibers are disposed in a straight and planar manner as in the axial direction. Therefore, the medium elongation diagonal fibers 46 are selected so that the maximum strain of the undulated medium elongation diagonal fibers 46 is more than the yield strain of steel (about 0.2% for Grade 60 steel) and slightly less than the expected maximum strain before debonding of the strengthening material from the concrete surface usually experienced by shear strengthening cases (the effective strain).
  • the high elongation diagonal fibers 48 are selected so that the undulated high elongation diagonal fibers 48 can sustain the load along with the axial yarns up to the total failure of the fabric.
  • the triaxial fabric 40 is completed by combining the axial and diagonal fibers in accordance with the fabric mix and impregnating the mix inside a mold with a high strength matrix such as epoxy or high strength cement slurry.
  • the triaxial fabric 40 was tested on a reinforced concrete beam having the same cross sectional dimensions and reinforcement as the test beams for the uniaxial fabric.
  • the test sample of the triaxial fabric 40 had a thickness of 3.5 mm ( 0.14 in.).
  • the tested triaxial fabric 40 included repeating cells of one low elongation axial fiber 14 made from 24k of Dialead® K63712, one medium elongation axial fiber 18 made from 108k of Torayca®, four high elongation axial fibers 16 made from 68.9 yd/lb of Hybon® 2022 glass, two medium elongation diagonal fibers 46 made from 108k of Torayca® M46 carbon fibers, and ten high elongation diagonal fibers 48 made from 118.1 yd/lb of Hybon® 2022 glass fibers.
  • the spacing between axial fibers 14, 16 and 18 was 0.25 inches and the spacing between the diagonal fibers was 0.1768 inches.
  • the same epoxy resin used in the uniaxial test fabric was impregnated into the triaxial fabric 40 and used to adhere the triaxial fabric 40 to the appropriate surface(s) of the concrete beams.
  • the epoxy again had an ultimate strain of 4.4 % to insure that the epoxy would not fail before failure of the high elongation axial and diagonal fibers.
  • FIGS. 14 and 15 illustrate simple beam two-point load test results for the beam strengthened with the above-described triaxial fabric 40 along only the bottom surface of the beams.
  • FIG. 14 shows the load versus mid-span deflection response 52 for the fabric strengthened beam as compared to the load versus mid-span deflection response 32 for the control beam 8.
  • a yield load of 111.3 kN ( 25.0 kips) was experienced which is a 35% percent increase in yield load over that of the control beam.
  • FIG. 15 illustrates the test beam strain at mid-span showing that the triaxial fabric 40 had strain of approximately 0.35% when the beam which indicates that it yielded simultaneously with the steel reinforcement.
  • the ductile structural fabric of the present invention provides significant benefits for strengthening steel-reinforced concrete beams.
  • the fabric, and particularly the triaxial fabric 40 is suitable for a wide array of uses beyond strengthening structural components such as steel reinforced concrete.
  • the fabric may be used to strengthen other structural components such as steel beams.
  • the high strength, ductile, and lightweight properties of the fabric may be capitalized upon to increase a structure's resistance to attack such as from impact forces.
  • impact forces the yielding of the fabric assists in dissipating energy from impact before failure takes place.
  • Various manufacturing techniques generally known in the art may be used to develop various solid shapes and configurations using the fabric of the present invention to create vehicle or aircraft components such as body panels, tracks, and wheels. These components will be generally stronger and lighter in weight than currently available components.

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  • Engineering & Computer Science (AREA)
  • Architecture (AREA)
  • Civil Engineering (AREA)
  • Structural Engineering (AREA)
  • Manufacturing & Machinery (AREA)
  • Textile Engineering (AREA)
  • Chemical & Material Sciences (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Electrochemistry (AREA)
  • Mechanical Engineering (AREA)
  • Woven Fabrics (AREA)

Abstract

L'invention concerne un tissu structurel (1) présentant une première fibre dotée d'une contrainte limite et une seconde fibre dotée d'une contrainte limite supérieure à la première force finale, la première et seconde fibre étant dans le même plan. L'invention concerne également un tissu structurel présentant une pluralité de fibres axiales et une pluralité de premières fibres diagonales tressées avec lesdites fibres axiales et orientées dans un premier angle de tressage relatif audit tressage. Ladite contrainte limite de ladite seconde fibre est supérieure à la contrainte limite de la première fibre. L'invention concerne de plus une ensouple (8) en béton consolidée par lesdites fibres structurelles de l'invention.
PCT/US2002/037608 2001-12-19 2002-12-16 Tissu structurel hybride ductile WO2003053679A1 (fr)

Priority Applications (1)

Application Number Priority Date Filing Date Title
AU2002346493A AU2002346493A1 (en) 2001-12-19 2002-12-16 Ductile hybrid structural fabric

Applications Claiming Priority (4)

Application Number Priority Date Filing Date Title
US60/342,027 2001-12-19
US60/342,026 2001-12-19
US10/164,737 2002-06-07
US10/164,737 US6790518B2 (en) 2001-12-19 2002-06-07 Ductile hybrid structural fabric

Publications (1)

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WO2003053679A1 true WO2003053679A1 (fr) 2003-07-03

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Cited By (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE102008026615A1 (de) * 2008-05-30 2009-12-03 Sächsisches Textilforschungsinstitut e.V. Hybride textile Bewehrung von Mauerwerk, textilbewehrte Bauelemente bzw. Verstärkungsschichten für Bauelemente und Verfahren zu deren Herstellung und Einsatz
WO2011045505A1 (fr) 2009-10-15 2011-04-21 Universite Claude Bernard Lyon I Element de renforcement en composite fibres-ciment et procede de renforcement de structures en beton arme par un tel element
IT201700109689A1 (it) * 2017-09-29 2019-03-29 Spa Fratelli Citterio Elemento strutturale in calcestruzzo armato e metodo per la realizzazione dello stesso.
EP3460114A3 (fr) * 2017-09-15 2019-04-10 Universität Stuttgart Structure composite renforcée par fibres, noeuds de raccordement destinés à la construction de bâtiments et procédé de fabrication de noeuds de raccordement destinés à la construction de bâtiments
US11768193B2 (en) 2019-12-20 2023-09-26 The Research Foundation For The State University Of New York System and method for characterizing the equibiaxial compressive strength of 2D woven composites

Citations (3)

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Publication number Priority date Publication date Assignee Title
US4438173A (en) * 1983-07-21 1984-03-20 Barber-Colman Company Triaxial fabric
US5677046A (en) * 1992-09-09 1997-10-14 Clock Spring Company L.P. High tensile strength composite reinforcing bands
US5727357A (en) * 1996-05-22 1998-03-17 Owens-Corning Fiberglas Technology, Inc. Composite reinforcement

Patent Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4438173A (en) * 1983-07-21 1984-03-20 Barber-Colman Company Triaxial fabric
US5677046A (en) * 1992-09-09 1997-10-14 Clock Spring Company L.P. High tensile strength composite reinforcing bands
US5727357A (en) * 1996-05-22 1998-03-17 Owens-Corning Fiberglas Technology, Inc. Composite reinforcement

Cited By (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE102008026615A1 (de) * 2008-05-30 2009-12-03 Sächsisches Textilforschungsinstitut e.V. Hybride textile Bewehrung von Mauerwerk, textilbewehrte Bauelemente bzw. Verstärkungsschichten für Bauelemente und Verfahren zu deren Herstellung und Einsatz
WO2011045505A1 (fr) 2009-10-15 2011-04-21 Universite Claude Bernard Lyon I Element de renforcement en composite fibres-ciment et procede de renforcement de structures en beton arme par un tel element
FR2951483A1 (fr) * 2009-10-15 2011-04-22 Univ Claude Bernard Lyon Element de renforcement en composite fibres-ciment et procede de renforcement de structures en beton arme par un tel element
EP3460114A3 (fr) * 2017-09-15 2019-04-10 Universität Stuttgart Structure composite renforcée par fibres, noeuds de raccordement destinés à la construction de bâtiments et procédé de fabrication de noeuds de raccordement destinés à la construction de bâtiments
IT201700109689A1 (it) * 2017-09-29 2019-03-29 Spa Fratelli Citterio Elemento strutturale in calcestruzzo armato e metodo per la realizzazione dello stesso.
WO2019064211A1 (fr) * 2017-09-29 2019-04-04 Societa' Per Azioni Fratelli Citterio Élément structural en béton armé et son procédé de fabrication
US11768193B2 (en) 2019-12-20 2023-09-26 The Research Foundation For The State University Of New York System and method for characterizing the equibiaxial compressive strength of 2D woven composites

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