Seismic behaviors of reinforced concrete column confined by bidirectional fiber reinforced polymer composite with anchor
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摘要: 双向纤维增强聚合物(Fiber reinforced polymer,FRP)复合材料布具有良好的两向正交抗拉性能,与传统单向布相比,使用其约束加固柱时能使构件获得抗剪、抗弯承载力和抗震延性的同时提高。开展了基于纤维锚钉锚固的双向布约束加固钢筋混凝土柱低周反复加载试验,参数包含布种类、层数和锚固方式,研究了加固柱的破坏模式、抗震性能和材料应变。 结果表明,柱在约束加固前后的破坏形态由剪切转变为弯曲破坏,构件延性大幅度提高;同层数的双向纤维布在环向应变值发挥少于单向布;使用锚钉可显著提升双向布纵向纤维应变,其应变值比未锚固前的提高了约1.5倍;并进一步提高约束柱抗弯承载力,较未加锚固前的约束柱承载力提高了2.9%~7.1%。成果可为双向纤维布在既有结构加固领域的应用提供指导。
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关键词:
- 双向纤维增强树脂复合材料布 /
- 约束 /
- 钢筋混凝土柱 /
- 锚钉 /
- 抗震性能
Abstract: The bidirectional fibers reinforced polymers (FRP) sheets have good tensile properties in two orthogonal direction. Compared with using traditional unidirectional fabrics, the seismic ductility, shear and flexural capacities of strengthened columns confined by bidirectional FRP sheets are simultaneously improved. Based on using bidirectional FRP sheets with fiber anchors, six reinforced concrete columns were tested under low cyclic lateral loading. The experimental parameters included FRP types, layer number and anchorage schemes, which were intended to study the failure mode, seismic performance and material strain of different confined columns. The test results show that the failure mode of the columns changes from shear to bending failure after confinement, and the hoop working strain of bidirectional FRP sheets is less than that of unidirectional FRP sheets under the same layers. The effective strain of longitudinal fibers in bidirectional FRP sheets significantly increases when using FRP anchor, the fiber strain value is about 1.5 times higher than that before the anchorage, which further improves the flexural capacity of confined columns, the bearing capacities of the confined columns increase by 2.9%-7.1% than that before the anchorage. The research results provide guidance for the application of bidirectional FRP sheets in strengthening existing reinforced concrete structure.-
Key words:
- bidirectional FRP sheets /
- confinement /
- reinforced concrete column /
- anchor /
- seismic performance
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图 1 试验柱的尺寸、配筋、量测和加固方案
FRP—Fiber reinforced polymer; Z or F—Strain gauge type on the longitudinal rebar or the FRP sheets, and the first number after the letter represents the plan position, while the second number represents the height position
Figure 1. Dimensions, reinforcement, measurement and strengthening schemes of experimental columns
表 1 玄武岩纤维增强复合材料(BFRP)布加固钢筋混凝土(RC)柱主要设计参数
Table 1. Main design parameters of reinforced concrete (RC) columns strengthened with basalt fiber reinforced polymer (BFRP)
Specimen BFRP type BFRP layer Number of anchor C – 0 0 U1 Unidirectional 1 0 B1 Bidirectional 1 0 B2 Bidirectional 2 0 B1 A Bidirectional 1 4 B2 A Bidirectional 2 4 Notes: C—Control column; U1—Strengthened with one layer unidirectional BFRP sheets; B1 and B2—Strengthened with one and two layers bidirectional BFRP sheets; B1 A and B2 A—Strengthened with bidirectional BFRP sheets and anchors. 表 2 混凝土材料力学性能
Table 2. Mechanical property of concrete
Material Cube compressive
strength/MPaPrismatic compressive
strength/MPaElastic modulus/MPa Concrete 32.8 21.9 3.18×104 表 3 钢材力学性能
Table 3. Mechanical properties of steel
Material Yield strength/MPa Ultimate strength/MPa Elastic modulus/MPa Longitudinal rebar 472 608 2.18×105 Stirrup 385 470 2.38×105 表 4 纤维布和浸渍胶材料力学性能
Table 4. Mechanical properties of FRP and resin
Material Compressive strength/MPa Young's module/GPa Tensile strength/MPa Elongation
/%Thickness
/mmUnidirectional FRP – 82.0 1230.0 2.0 0.37 Bidirectional FRP – 82.0 1230.0 2.0 0.33 Resin 82.6 3.2 48.5 1.9 – 表 5 双向BFRP布加固RC柱抗震试验结果
Table 5. Seismic test results of RC columns strengthened with bidirectional BFRP sheets
Specimen Δy/mm Δc/mm Δu/mm Py/kN Pc/kN μΔ/mm Esum/(kN·m) $ {\xi _{\text{e}}} $ C 11.0 22.5 27.5 87.4 119.7 2.5 11.0 0.153 U1 11.2 40.0 60.0 108.9 131.5 5.4 47.4 0.192 B1 10.0 40.0 55.0 104.1 130.0 5.5 44.3 0.156 B1 A 12.0 40.0 52.5 111.6 133.8 4.4 39.2 0.155 B2 14.0 90.0 115.0 115.5 136.5 8.2 141.5 0.173 B2 A 15.0 70.0 130.0 121.4 146.2 8.7 155.3 0.160 Notes: Δy—Displacement of column top at yielding load; Δc—Displacement at ultimate load; Δu—Ultimate displacement when the load drops to 85% of the peak load; Py—Yielding lateral load; Pc—Ultimate lateral load; μΔ—Displacement ductility factor that is the ratio of Δu to Δy; Esum—Total accumulative dissipated energy at the ultimate state; ξe—Equivalent viscous damping ratio at the ultimate state. 表 6 BFRP布加固RC柱抗震承载力试验值与计算值对比
Table 6. Comparison of experimental and calculated seismic bearing capacity of RC columns strengthened with BFRP sheets
Specimen εfe,x/10−6 εfe,y/10−6 εcc,u/10−6 βj fcc/MPa Fc/kN Fe/kN Fc/Fe U1 8250 0 4531 6.53 19.77 114.13 131.50 0.87 B1 5250 5250 3635 2.91 19.85 114.01 130.00 0.88 B1 A 5250 7875 3635 2.91 19.85 121.39 133.80 0.91 B2 5250 5250 3883 5.83 21.15 114.57 136.50 0.84 B2 A 5250 7875 3883 5.83 21.15 129.12 146.20 0.88 Notes: εfe,x—Effective strain of circumferential fiber of FRP sheets; εfe,y—Effective strain of longitudinal fiber; εcc,u—Ultimate compressive strain of confined concrete; βj—Confinement stiffness parameter; fcc—Compressive strength of confined concrete; Fc—Calculated value of bearing capacity; Fe—Tested value of bearing capacity. -
[1] 冯鹏, 陆新征, 叶列平. 纤维增强复合材料建设工程应用技术[M]. 北京: 中国建筑工业出版社, 2011.FENG Peng, LU Xinzheng, YE Lieping. Application of fiber reinforced polymer in construction[M]. Beijing: China Architecture and Building Press, 2011(in Chinese). [2] LEE H K, CHEONG S H, HA S K, et al. Behavior and performance of RC T-section deep beams externally strengthened in shear with CFRP sheets[J]. Composite Structures,2011,93(2):911-922. doi: 10.1016/j.compstruct.2010.07.002 [3] ATTARI N, AMZIANE S, CHEMROUK M. Flexural strengthening of concrete beams using CFRP, GFRP and hybrid FRP sheets[J]. Construction and Building Materials,2012,37:746-757. doi: 10.1016/j.conbuildmat.2012.07.052 [4] CAMPIONE G, MENDOLA L L, MONACO A, et al. Behavior in compression of concrete cylinders externally wrapped with basalt fibers[J]. Composites Part B: Engineering,2015,69:576-586. doi: 10.1016/j.compositesb.2014.10.008 [5] 高鹏, 赵元鸿, 洪丽, 等. 圆角半径对碳纤维增强聚合物复合材料布约束型钢混凝土矩形短柱轴压性能的影响[J]. 复合材料学报, 2020, 37(4):775-785. doi: 10.13801/j.cnki.fhclxb.20190627.001GAO Peng, ZHAO Yuanhong, HONG Li, et al. Effect of corner radius on axial compressive performance of steel reinforced concrete rectangular short columns confined by CFRP[J]. Acta Materiae Compositae Sinica,2020,37(4):775-785(in Chinese). doi: 10.13801/j.cnki.fhclxb.20190627.001 [6] 王作虎, 杨菊, 崔宇强, 等. 碳纤维增强树脂复合材料加固钢筋混凝土柱抗震性能的尺寸效应试验[J]. 复合材料学报, 2020, 37(10):2645-2655. doi: 10.13801/j.cnki.fhclxb.20200212.001WANG Zuohu, YANG Ju, CUI Yuqiang, et al. Experiment on the size effect of seismic behavior for reinforced concrete columns strengthened by carbon fiber reinforced plastics[J]. Acta Materiae Compositae Sinica,2020,37(10):2645-2655(in Chinese). doi: 10.13801/j.cnki.fhclxb.20200212.001 [7] American Concrete Institute. Guide for the design and construction of externally bonded FRP systems for strengthening concrete structures: ACI 440.2R-08[S]. Farmington Hills: American Concrete Institute, 2008. [8] 中华人民共和国住房和城乡建设部. 纤维增强复合材料工程应用技术标准: GB/T 50608—2020[S]. 北京: 中国计划出版社, 2020.Ministry of Housing and Urban-Rural Development of the People’s Republic of China. Technical standard for fiber reinforced polymer (FRP) in construction: GB/T 50608-2020[S]. Beijing: China Planning Press, 2020(in Chinese). [9] GALAL K, ARAFA A, GHOBARAH A. Retrofit of RC square short columns[J]. Engineering Structures,2005,27(5):801-813. doi: 10.1016/j.engstruct.2005.01.003 [10] ANDREW S. Strengthening reinforced concrete bridge T-beams with CFRP sheets plus bidirectional GFRP U-wraps[D]. Kansas: Kansas State University, 2019. [11] FLORES I, JF GÓMEZ, PV LLAURADÓ, et al. Evaluation through a finite element simulation of the performance of FRP anchors for externally bonded reinforcements[J]. Composite Structures,2021,267:113919. [12] FU B, TANG X T, LI L J, et al. Inclined FRP U-jackets for enhancing structural performance of FRP plated RC beams suffering from IC debonding[J]. Composite Structures,2018,200:36-46. doi: 10.1016/j.compstruct.2018.05.074 [13] GALAL K, MOFIDI A. Shear strengthening of RC T-beams using mechanically anchored unbonded dry carbon fiber sheets[J]. Journal of Performance of Constructed Facilities,2010,24(1):31-39. doi: 10.1061/(ASCE)CF.1943-5509.0000067 [14] HUGO C, MANUE A, CARLOS C, et al. Factors influencing the performance of externally bonded reinforcement systems of GFRP-to-concrete interfaces[J]. Materials and Structures,2015,48(9):2961-2981. doi: 10.1617/s11527-014-0370-z [15] BARBIERI G, BIOLZI L, BOCCIARELLI M, et al. Size and shape effect in the pull-out of FRP reinforcement from concrete[J]. Composite Structures,2016,143:395-417. doi: 10.1016/j.compstruct.2016.01.097 [16] WU Z S, HONG Y, TOSHIHIRO A, et al. Peeling behavior and spalling resistance of bonded bidirectional fiber reinforced polymer sheets[J]. Journal of Composites for Construction, 2005, 9(3): 214-226. [17] KALFAT R, AL-MAHAIDI R. Improvement of FRP to concrete bond performance using bidirectional fiber patch anchors combined with FRP spike anchors[J]. Composite Structures,2016,155(11):89-98. [18] 中华人民共和国住房和城乡建设部. 普通混凝土力学性能试验方法标准: GB/T 50081—2002[S]. 北京: 中国建筑工业出版社, 2003.Ministry of Housing and Urban-Rural Development of the People’s Republic of China. Standard for test method of mechanical properties on ordinary concrete: GB/T 50081-2002[S]. Beijing: China Architecture and Building Press, 2003(in Chinese). [19] 中华人民共和国国家质量监督检验检疫总局. 金属材料拉伸试验第1部分: 室温试验方法: GB/T 228.1—2010[S]. 北京: 中国标准出版社, 2010.General Administration of Quality Supervision, Inspection and Quarantine of the People’s Republic of China. Metallic materials—Tensile testing—Part 1: Method of test at room temperature: GB/T 228.1—2010[S]. Beijing: Standards Press of China, 2010(in Chinese). [20] 中华人民共和国住房和城乡建设部. 混凝土结构后锚固技术规程: JGJ 145—2013[S]. 北京: 中国建筑工业出版社, 2013.Ministry of Housing and Urban-Rural Development of the People’s Republic China. Technical specification for post-installed fastenings in concrete structures: JGJ 145—2013[S]. Beijing: China Architecture and Building Press, 2013(in Chinese). [21] CASTILLO E, GRIFFITH M, INGHAM J. Straight FRP anchors exhibiting fiber rupture failure mode[J]. Composite Structures,2019,207(1):612-624. [22] KIM S, SMITH S. Pullout strength models for FRP anchors in uncracked concrete[J]. Journal of Composites for Construction,2010,14(4):406-414. doi: 10.1061/(ASCE)CC.1943-5614.0000097 [23] CASTILLO E, KANITKAR R, SMITH S. Design approach for FRP spike anchors in FRP strengthened RC structures[J]. Journal of Composites for Construction,2019,214(2):23-33. [24] 黄镜渟, 周安, 詹炳根, 等. 玄武岩纤维布的力学性能和强度利用率研究[J]. 工业建筑, 2019, 49(3):1-5. doi: 10.13204/j.gyjz201903001HUANG Jingting, ZHOU An, ZHAN Binggen, et al. Research on mechanical properties and strength efficiency of basalt fiber fabric-reinforced epoxy composites[J]. Industrial Construction,2019,49(3):1-5(in Chinese). doi: 10.13204/j.gyjz201903001 [25] VECCHIO C D, LUDOVICO M D, PROTA A, et al. Analytical model and design approach for FRP strengthening of non-conforming RC corner beam-column joints[J]. Engineering Structures,2015,87(15):8-20.