A review of the studies on concrete structures prestressed with external fiber reinforced polymer (FRP) tendons
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摘要: 本文从纤维增强树脂基复合材料(FRP)筋、关键技术和构件三个主要方面综述了体外预应力FRP筋混凝土结构的研究成果:①介绍了预应力FRP筋拉伸性能和长期性能,给出了面向设计的FRP筋蠕变断裂应力值、松弛率以及疲劳最大应力和应力幅限值。②阐述了预应力FRP筋三种主要锚固技术的优缺点和减小锚固端应力集中的方法,重点介绍了近年来新开发的复合材料夹片锚具,其锚固效率系数高于90%;同时,基于转向FRP筋力学性能试验结果,建议转向半径不宜小于FRP筋半径的200倍,转向角度不宜大于5°。③梳理了体外预应力FRP筋混凝土构件的试验研究结果(单调加载、长期持荷和循环加载),介绍了国内外规范中的设计方法,并基于既有文献中42根梁的试验结果评价了规范中计算方法的精度,验证了我国规范GB 50608—2020中体外预应力FRP筋混凝土结构设计计算方法的准确性。本综述将对体外预应力FRP筋混凝土结构的推广应用起到积极推动作用。Abstract: The studies on concrete structures prestressed with external FRP tendons are reviewed in the aspects of FRP tendon, key technology and structural component, in this review. Firstly, the tensile properties and long-term behaviors of FRP tendon are introduced. The design-oriented values of creep-rupture stress, relaxation rate and the limits of maximum fatigue stress and fatigue stress range are provided. Secondly, the advantages and deficiencies of three main types of anchor for FRP tendon, and the methods of reducing the stress concentration on FRP tendon at anchor are elaborated. The newly-developed composite-wedge anchor is emphasized, which possesses an anchor efficiency coefficient exceeding 90%. Meanwhile, the deviation radius is recommended to be larger than 200 times of the radius the cross-section of FRP tendons, and the deviation angle of FRP tendons should not exceed 5°, based on the experimental results on the mechanical properties of deviated FRP tendons. Thirdly, the experimental results of concrete beams prestressed with external FRP tendons are reviewed, including monotonic loading, sustained loading and cyclic loading. The design methodologies in the codes at home and overseas are introduced. The accuracies of the calculating methods in the codes are evaluated using the experimental data of forty-two beams, and the methods in the Chinese code GB 50608—2020 are validated to be accurate in the design calculation for concrete structures prestressed with external FRP tendons. This paper is expected to actively promote the popularization and application of concrete structures prestressed with external FRP tendons.
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图 2 FRP筋蠕变松弛性能提升机制示意图[20]
Figure 2. Schematic diagram for the improvement mechanism of creep and relaxation behaviors of FRP tendons
图 3 FRP筋内部初始弯曲纤维与预张拉后的拉直纤维[17]
Figure 3. Initial uneven fibers and straightened fibers after pretensioned in a FRP tendon
图 4 图4 玄武岩纤维增强树脂基复合材料(BFRP)筋疲劳破坏机制[22]
Figure 4. Mechanism of the fatigue failure of basalt fiber reinforced polymer (BFRP) tendon
图 6 分段式复合材料夹片[38]
Figure 6. Segmented composite wedge
图 7 图7 FRP筋转向区试验装置[39]
Figure 7. Test setup for FRP tendons at a deviator
图 8 图8转向角度和转向半径对弯折FRP筋承载力保留率的影响[39]
Figure 8. Effects of deviation radius and angle on the loading capacity of FRP tendon at deviator
表 1 FRP筋、高强钢筋、钢绞线拉伸性能[8]
Table 1. Tensile properties of FRP tendons, high-strength steel bar and steel strand
Type of
tendonDensity/
(g/cm3)Tensile
strength/MPaElastic
modulus/GPaElongation/
%Longitudinal thermal
expansivity/(10−6/℃)CFRP tendon 1.5 1500~2500 120~160 0.5~1.7 −2~0 BFRP tendon 2.0 800~1800 50~60 1.6~3.0 6~8 AFRP tendon 1.4 1000~2 000 40~120 1.9~4.4 −6~−2 High-strength steel bar 7.85 490~700 200 >10 11.7 Steel strand 7.85 1400~1 860 180~200 >4 11.7 表 2 FRP筋的蠕变断裂应力
Table 2. Values of creep rupture stress of FRP tendons
表 3 FRP筋蠕变断裂应力建议值
Table 3. Recommended values of the creep rupture stress of FRP tendons
Type of tendon CFRP AFRP BFRP Creep rupture stress 0.70fu 0.55fu 0.54fu fu is the tensile strength of FRP tendon. 表 4 0.5fu初始应力下FRP筋百万小时松弛率预测值
Table 4. Predictive values of the one-million-hour relaxation rates of FRP tendons at a 0.5fu initial level
Type of tendon CFRP AFRP BFRP Relaxation rate 3.0% 10~13% 6.7% 表 5 FRP筋疲劳强度(括号中为对应的应力幅)
Table 5. Values of the fatigue strength of FRP tendons (with the corresponding stress range in the brackets)
References CFRP AFRP BFRP Saadatmanesh[23-24] 0.9fu (0.05fu) 0.5fu (0.025fu) / Adimi et al.[27] 0.35fu (0.21fu) / / El Refai[25,28] 0.5fu (0.1fu) / 0.39fu (0.04fu) Song et al.[29] 0.64fu (0.09fu)
0.53fu (0.19fu)
0.37fu (0.28fu)
/ / Xie et al.[30] 0.5fu (0.09fu) / / Zhuge et al.[31] 0.42fu (0.04fu) / / Zhang and Ou[32] 0.5fu (0.25fu) / / Odagiri et al.[33] / 0.54fu (0.05 fu) / Wang et al.[22] / / 0.6fu (0.05fu) Atutis et al.[34] / / 0.65fu (0.07fu) fu is the tensile strength of FRP tendon. 表 6 FRP筋主要锚具形式的优缺点
Table 6. Advantages and deficiencies of the main types of anchor for FRP tendons
Type of anchor Advantages Deficiencies Bond type No radial stress, hence inducing no decrease in strength of tendon Inconvenient grouting; prestress loss due to long-term creep deformation of the bonding material in anchor Friction type Radial stress is beneficial for the long-term
behavior of anchorInconvenient grouting Wedge type Convenient assembly Notch effect on FRP tendon 表 7 FRP筋张拉控制应力σcon
Table 7. Tension control stress σcon of FRP tendons
Type of FRP CFRP AFRP BFRP Upper limit 0.65 fu 0.55 fu 0.50 fu Lower limit 0.50 fu 0.35 fu 0.35 fu fu is the tensile strength of FRP tendon. 表 8 不同R/r下的弯折FRP筋强度折减系数
Table 8. Strength reduction coefficients of deviated FRP tendon at different values of R/r
R/r CFRP tendon AFRP tendon BFRP tendon 200 0.61 0.75 0.79 300 0.74 0.83 0.86 400 0.81 0.88 0.89 表 9 体外预应力FRP筋混凝土梁抗弯性能研究数据库
Table 9. Database of the studies on the flexural behaviors of concrete beams prestressed with external FRP tendons
表 10 体外预应力FRP筋混凝土梁长期性能研究数据库
Table 10. Database of the studies on the long-term behaviors of concrete beams prestressed with external FRP tendons
表 11 体外预应力FRP筋极限状态应力增量Δσpu的试验值与理论值之比
Table 11. Ratios of experimental value to theoretical value of the stress increment Δσpu of external prestressing FRP tendons at ultimate state
Codes ACI 440.4R BS 8110 fib GB 50608 Average value 1.39 2.14 1.58 1.01 Variance 0.58 0.89 0.45 0.20 表 12 体外预应力FRP筋混凝土梁抗弯承载力的试验值与理论值之比
Table 12. Ratios of experimental value to theoretical value of the flexural capacity of concrete beams prestressed with external FRP tendons
Codes ACI 440.4R BS 8110 fib GB 50608 Average value 1.09 1.47 1.10 1.05 Variance 0.15 0.22 0.13 0.07 表 13 预应力FRP筋混凝土梁裂缝宽度的试验值与理论值之比
Table 13. Ratios of experimental value to theoretical value of the crack width of concrete beams prestressed with external FRP tendons
Codes ACI 440.4R fib GB 50608 Average value 0.94 1.03 0.92 Variance 0.53 0.59 0.65 表 14 预应力FRP筋混凝土梁挠度的试验值与理论值之比
Table 14. Ratios of experimental value to theoretical value of the deflection of concrete beams prestressed with external FRP tendons
Codes ACI 440.4R fib GB 50608 Average value 0.94 0.95 0.92 Variance 0.34 0.38 0.25 表 15 预应力FRP筋混凝土梁长期挠度(反拱)试验结果与AEMM计算的理论值之比
Table 15. Ratios of experimental value to theoretical value calculated using AEMM of the long-term deflection (camber) of concrete beams prestressed with external FRP tendons
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