Use of Fiber-Reinforced Polymers in Highway Infrastructure (2017) / Chapter Skim
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19 chapter five State of the art of fiber-reinforced Polymer comPoSiteS in highway infraStructure fiber-reinforced Polymer-reinforced concrete memberS This section provides an overview of FRP-reinforced concrete members and their behavior under flexure, shear, and axial loadings. Miscellaneous subjects such as bond and development are discussed as well.
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20 FIGURE 3 Stress-strain relationship of GFRP bar (reproduced based on Hughes Brothers' data sheet)
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21 collected from manufacturers in the United States are summarized in Table 6. It is worth noting that (1)
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22 beams. The post-cracking flexural rigidity of FRP-reinforced concrete beams increases as the reinforcement ratio rises (Tomlinson and Fam 2015)
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23 Shear behavior Concrete beams reinforced with longitudinal FRP bars demonstrate shear behavior analogous to steel-reinforced beams (Pantelides et al.
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24 0.017 in.
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25 affect the compressive strength and modulus of FRP reinforcing bars; for example, fiber types, fiber-resin volume fraction ratios, manufacturing methods, and geometric configurations (Tobbi et al.
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26 FRP and steel ties show intrinsically the same performance, as far as their contribution to column capacity is concerned (De Luca et al.
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27 such as deformability (Prachasaree et al.
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28 expected, attention needs to be paid because the properties of FRP bars change (i.e., the strength and stiffness of FRP decrease if the glass transition temperature of the resin is exceeded)
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29 members. Mufti et al.
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30 The manufacturer-reported strength of FRP reinforcement may be reduced by environmental reduction factors, given that several external attributes can degrade the long-term performance of FRP bars (e.g., creep, fatigue, acid, alkali, and moisture)
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31 ment (in.)
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32 dohteM ecruoS AASHTO guide specifications (AASHTO 2009) Use the effective moment of inertia (Ie)
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33 dohteM ecruoS AASHTO guide specifications (AASHTO 2009) 4 2 2 2, sdk E f w cb f sf += β where (U.S.
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TABLE 10 (continued) dohteM ecruoS fib Bulletin No.
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35 Source Development Length (ld) AASHTO guide specifications (AASHTO 2009)
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36 and conventional theory (e.g., modified compression field theory) is applicable (Liu and Pantelides 2012)
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38 Source Component AASHTO guide specifications (AASHTO 2009) cbfcbfV cwcc 0 '' 32.016.0 ≤= s dfA V fvfvf = where (U.S.
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39 fully reinforced with GFRP bars, the Val-Alain Bridge, was constructed in 2004 (Benmokrane et al.
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40 Benmokrane et al.
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44 frP tendons Various FRP tendons are available in terms of material composition and geometric properties. Carbon fibers are most commonly used, followed by aramid fibers.
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45 prestressed concrete beams with unbonded FRP tendons is different from the response of those with bonded tendons [Figure 17(b)
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46 (Abdelrahman and Rizkalla 1999)
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49 durability FRP-prestressed concrete beams show a stiffness decrease under fatigue loading (Grace 2000; Mertol et al.
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51 a marine environment (i.e., load-carrying capacity, ductility, and failure mode) , primarily as a result of the degradation of GFRP tendons (Sen et al.
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52 Because FRP tendons do not yield, the concept of ductility (the ratio between ultimate and yield responses) is not applicable.
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53 Shear Design The shear reinforcement of FRP-prestressed concrete beams can be either steel or FRP stirrups. If steel stirrups are used, design approaches are identical to those for conventional prestressed concrete beams.
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59 FIGURE 27 FRP strengthening methods (used by permission from Yail J
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60 of NSM CFRP's improved bond performance, the beam strengthened with NSM CFRP shows a higher failure load than the beam with EB CFRP [Figure 28(a)
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61 FIGURE 29 Failure modes of FRP-strengthened beams in flexure (used by permission from Yail J
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65 Composite action between the strengthened member and post-tensioned NSM CFRP is crucial to achieving structural integrity. Because of the confining effect provided by the post-tensioned NSM CFRP, the strengthened beams tend to show reduced crack spacing compared with those strengthened with nonprestressed NSM CFRP (Ye et al.
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66 et al.
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68 FIGURE 34 CFRP-confinement for axial concrete members (used by permission from Yail J
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69 the shape of a rectangular column (e.g., oval shape) , so that the efficacy of FRP-confining can be enhanced (Yan and Pantelides 2011)
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73 of increasing the strength and ductility of strengthened concrete exposed to aggressive environments (Toutanji 1999; Davalos et al.
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74 bridge columns are wrapped with FRP sheets. Design approaches for FRP-strengthened concrete members are similar to the approaches for conventional reinforced concrete (i.e., strain compatibility and force equilibrium)
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76 reported by the manufacturer. The AASHTO guide specifications state that the factored resistance of FRP-strengthened members and load combinations are calculated according to the AASHTO LRFD BDS (AASHTO 2012a)
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77 Source Limit AASHTO guide specifications (AASHTO 2012a) c c c E f '36.0≤ ys 8.0≤ where c = concrete strain s = steel strain ' cf = concrete strength in compression cE = elastic modulus of concrete y = yield strain of steel.
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78 When FRP sheets are bonded (e.g., U-wraps) , the corners of the beam to be strengthened are chamfered to reduce stress concentrations.
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79 reinforced concrete) is not necessary.
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80 Source Equation Intelligent Sensing for Innovative Structures (ISIS Canada 2008a) fufe 75.0≤ for FRP strength 004.0≤fe for aggregate interlock fuvfe K≤ for bond capacity 75.0 11900 21 ≤= fu e v LkkK 3/2 ' 1 27 = cfk fv efv d Ld k − =2 ( )
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81 Source Equation AASHTO guide specifications (AASHTO 2012a) += c l ccc f fff 21'' −≤= 75.01 2 2 65.0 ' e cfrp l k f D N f where cf = stress in concrete at strain c frpN = strength per FRP width corresponding to a strain of 0.004 D = external diameter of column ek = constant ( ek = 0.80 and 0.85 for tied and spiral columns, respectively)
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82 Site application FRP strengthening technologies have been used for bridge structures for more than 20 years. The application of FRP is virtually unlimited from bridge superstructure to substructure.
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83 FIGURE 39 (Continued) FRP strengthening of deficient bridge members [Lopez and Nanni 2006; Banthia et al.
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87 FIGURE 41 Gandy Boulevard Bridge repair [Mullins et al. 2006 (used by permission from American Concrete Institute)
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94 Various anchor systems are available for post-tensioning CFRP sheets and laminates, as shown in Figure 46. Adjustable or movable mechanical anchors are frequently used to post-tension CFRP laminates [Figures 46(a)
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96 hexagonal structures)
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97 FIGURE 46 Various anchor systems for post-tensioned CFRP [Basler et al. 2004 (used by permission from Canadian Society for Civil Engineering)
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103 FIGURE 49 GFRP-repaired timber structures [Watson 2004 (used by permission from Canadian Society for Civil Engineering)
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106 Prefabricated FRP decks are positioned on top of bridge girders [Figure 51(a)
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111 may be exploited. The behavior of FRP stay-in-place members is generally similar to that of traditional structural members.
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113 (d) FIGURE 55 (Continued)
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114 FIGURE 57 FRP stay-in-place members [Nelson et al. 2014 (used by permission from American Concrete Institute)
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116 FIGURE 59 GFRP stay-in-place piles [Fam et al. 2003 (used by permission from Prestressed Concrete Institute and Sami Rizkalla)
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117 (d) FIGURE 59 (Continued)
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