Axial compressive behavior of FRP nonuniformly wrapped seawater sea-sand concrete in square columns
-
摘要: 为扩大纤维增强树脂复合材料(FRP)-海水海砂混凝土(SSC)组合结构的应用范围,改善FRP约束海水海砂混凝土柱脆性破坏特性,对碳纤维增强树脂复合材料(CFRP)非均匀约束海水海砂混凝土方柱的轴压性能进行了研究。试验结果表明:由于CFRP非均匀约束试件中沿高度方向CFRP厚度并不相等,因而整个破坏过程具有明显的预兆,故脆性行为得到明显改善。相比于相同体积率下的全包裹和条带约束试件,其具有更优越的力学性能,尤其是在净距比较小的情况下。随着外部CFRP条带净距的下降和层数的增加,试件的极限强度和变形能力显著提高。具体而言,由于FRP条带净距的降低导致试件的极限强度增幅在5.4%~18.5%不等,而在净距比固定状态下,当外部条带层数增大1倍后,极限强度与应变的最大增幅分别为15.8%和21.8%。最后基于试验数据,对现有部分代表性应力-应变模型对于非均匀约束混凝土的适用性进行了讨论,并给出了所有模型对于试件极限状态的预测精度与误差大小。
-
关键词:
- 纤维增强树脂复合材料 /
- 非均匀约束 /
- 约束混凝土 /
- 海水海砂混凝土 /
- 应力-应变模型
Abstract: To facilitate the practical application of fiber-reinforced polymer (FRP) strengthened seawater sea-sand concrete (SSC) structures in marine infrastructures and alleviate the brittleness of abrupt failure of FRP confined SSC columns, the mechanical performance of carbon fiber-reinforced polymer (CFRP) nonuniformly wrapped square SSC columns under axial compression was explored. Test results show that the failure pattern of nonuniformly CFRP confined square SSC columns exhibits less brittle since the rupture of thinner CFRP band between two adjacent strips can provide a warning sign due to the inequivalent number of CFRP layers at different locations along the height of the specimens. Compared to the specimens uniformly wrapped with CFRP sheets and strips under the same volumetric ratio of CFRP, CFRP nonuniformly wrapped SSC columns possess superior mechanical properties, especially for the specimens with a smaller clear spacing. Besides, with the decrease of clear spacing ratio and the increment of the thickness of external CFRP strips, the ultimate strengths and strains of confined specimens increase obviously. In specific, the enhancement of ultimate strengths ranges from 5.4%-18.5% as the decreasing of clear spacing ratio. Moreover, under the same clear spacing ratio, the maximum ultimate strength improvement and strain improvement are equal to 15.8% and 21.8% respectively when the thickness of external CFRP strips doubles. Finally, several representative stress-strain models were selected to examine their validity in predicting the ultimate conditions of FRP nonuniformly wrapped concrete and the accuracy and reliability of each model were also assessed.-
Key words:
- FRP /
- nonuniform confinement /
- confined concrete /
- seawater sea-sand concrete /
- stress-strain model
-
表 1 碳纤维增强树脂复合材料(CFRP)非均匀约束海水海砂混凝土(SSC)件参数和试验结果
Table 1. Details and test results of carbon fiber reinforced polymer (CFRP) nonuniformly wrapped seawater sea-sand concrete (SSC) specimens
Group Specimen ID w/mm s/mm s/b nP/ply Test results fcc/MPa fcc/fco fcu/MPa fcu/fco εcu/% εcu/εco εh,rup/% 1 C(W3A2F)S-1 30 105 0.7 2 47.4 1.31 42.6 1.17 1.21 6.05 1.08 C(W3A2F)S-2 30 105 0.7 49.2 1.36 43.7 1.20 1.39 6.93 1.17 C(W4A2F)S-1 40 90 0.6 51.3 1.41 45.8 1.26 1.49 7.46 1.19 C(W4A2F)S-2 40 90 0.6 50.7 1.40 45.1 1.24 1.37 6.83 1.20 C(W5A2F)S-1 50 75 0.5 52.6 1.45 49.5 1.36 1.57 7.86 1.25 C(W5A2F)S-2 50 75 0.5 51.9 1.43 46.9 1.29 1.43 7.14 1.02 C(W6A2F)S-1 60 60 0.4 52.7 1.45 50.5 1.39 1.87 9.37 1.20 C(W6A2F)S-2 60 60 0.4 51.8 1.43 48.8 1.34 1.72 8.62 1.15 C(W3B2F)S-1 30 30 0.2 52.4 1.44 50.4 1.39 1.97 9.83 1.28 C(W3B2F)S-2 30 30 0.2 53.0 1.46 51.9 1.43 2.03 10.15 1.30 2 C(W3A4F)S-1 30 105 0.7 4 50.5 1.39 50.5 1.39 1.62 8.08 1.11 C(W3A4F)S-2 30 105 0.7 49.0 1.35 49.0 1.35 1.45 7.27 0.92 C(W4A4F)S-1 40 90 0.6 51.7 1.43 51.7 1.43 1.62 8.12 1.22 C(W4A4F)S-2 40 90 0.6 53.6 1.48 53.6 1.48 1.44 7.22 1.13 C(W5A4F)S-1 50 75 0.5 53.0 1.46 53.0 1.46 1.74 8.69 1.16 C(W5A4F)S-2 50 75 0.5 55.1 1.52 55.1 1.52 1.92 9.59 1.17 C(W6A4F)S-1 60 60 0.4 58.0 1.60 58.0 1.60 2.23 11.16 1.21 C(W6A4F)S-2 60 60 0.4 56.8 1.56 56.8 1.56 1.91 9.55 1.15 C(W3B4F)S-1 30 30 0.2 59.2 1.63 59.2 1.63 2.17 10.87 1.26 C(W3B4F)S-2 30 30 0.2 58.7 1.62 58.7 1.62 2.54 12.71 1.23 Notes: In specimen ID: C—CFRP; W3, W4, W5, W6—Width of CFRP are 30 mm, 40 mm, 50 mm and 60 mm, respectively; A, B—CFRP number are 3 and 5, respectively; 2, 4—Layer number of CFRP; F—Bottom is wrapped with CFRP; S—SSC; 1, 2—Specimen number. fco—Compressive strength of unconfined concrete; w, s—Width and clear spacing of primary strips, respectively; b—Width of section edge; nP—Number of layers of external CFRP strips; fcc—Peak strength of confined concrete; fcu, εcu—Ultimate strength and corresponding strain of confined concrete, respectively; εh,rup—Hoop rupture strain of primary strips at the midheight outside the overlapping zone. -
[1] TENG J G, XIANG Y, YU T, et al. Development and mechanical behaviour of ultra-high-performance seawater sea-sand concrete[J]. Advances in Structural Engineering,2019,22(14):3100-3120. doi: 10.1177/1369433219858291 [2] 卢予奇, 赵羽习. 海砂颗粒形态评价与海拌混凝土性能研究[J]. 海洋工程, 2020, 38(6):124-130.LU Y Q, ZHAO Y X. Morphological evaluation of sea sand particles and basic properties of marine-mixed concrete[J]. The Ocean Engineering,2020,38(6):124-130(in Chinese). [3] XIAO J, QIANG C, NANNI A, et al. Use of sea-sand and seawater in concrete construction: Current status and future opportunities[J]. Construction and Building Materials,2017,155:1101-1111. doi: 10.1016/j.conbuildmat.2017.08.130 [4] 滕锦光. 新材料组合结构[J]. 土木工程学报, 2018, 51(12):1-11.TENG J G. New-material hybrid structures[J]. China Civil Engineering Journal,2018,51(12):1-11(in Chinese). [5] 张家玮, 邵利君, 刘生纬, 等. 硫酸盐环境中CFRP约束劣化混凝土柱的力学性能[J]. 复合材料学报, 2021, 38(3):996-978.ZHANG J W, SHAO L J, LIU S W, et al. Mechanical properties of CFRP confined pre-damaged concrete columns in sulfate environment[J]. Acta Materiae Compositae Sinica,2021,38(3):996-978(in Chinese). [6] 王桢, 亢景付, 王堃, 等. FRP锚钉锚固长度对FRP加固混凝土构件拉拔性能影响的试验研究[J]. 硅酸盐通报, 2017, 36(4):1365-1370.WANG Z, KANG J F, WANG K, et al. Experimental investigation on the pullout properties of concrete structures strengthened by FRP influenced by anchorage depth[J]. Bulletin of the Chinese Ceramic Society,2017,36(4):1365-1370(in Chinese). [7] 冯鹏, 王杰, 张枭, 等. FRP与海砂混凝土组合应用的发展与创新[J]. 玻璃钢/复合材料, 2014, 12:13-18.FENG P, WANG J, ZHANG X, et al. Development and innovation on combining FRP and sea sand concrete for structures[J]. Fiber Reinforced Plastics/Composites,2014,12:13-18(in Chinese). [8] CHEN G, LIU P, JIANG T, et al. Effects of natural seawater and sea sand on the compressive behaviour of unconfined and carbon fibre-reinforced polymer-confined concrete[J]. Advances in Structural Engineering,2020,23(14):3102-3116. doi: 10.1177/1369433220920459 [9] ZENG J J, GAO W Y, DUAN Z J, et al. Axial compressive behavior of polyethylene terephthalate/carbon FRP-confined seawater sea-sand concrete in circular columns[J]. Construction and Building Materials,2020,234:117383. doi: 10.1016/j.conbuildmat.2019.117383 [10] YANG J, WANG J, WANG Z. Axial compressive behavior of partially CFRP confined seawater sea-sand concrete in circular columns-Part I: Experimental study[J]. Composite Structures,2020,246:112373. doi: 10.1016/j.compstruct.2020.112373 [11] 柏佳文, 魏洋, 张依睿, 等. 新型碳纤维增强复合材料-钢复合管海水海砂混凝土圆柱轴压试验[J]. 复合材料学报, 2021, 38(9):3084-3093.BAI J W, WEI, Y, ZHANG Y R, et al. Axial compression behavior of new seawater and sea sand concrete filled circular carbon fiber reinforced polymer-steel composite tube columns[J]. Acta Materiae Compositae Sinica,2021,38(9):3084-3093(in Chinese). [12] LI Y L, ZHAO X L, RAMAN R S. Mechanical properties of seawater and sea sand concrete-filled FRP tubes in artificial seawater[J]. Construction and Building Materials,2018,191:977-993. doi: 10.1016/j.conbuildmat.2018.10.059 [13] PHAM T M, HADI M N S, YOUSSEF J. Optimized FRP wrapping schemes for circular concrete columns[J]. Journal of Composites for Construction,2015,19(6):04015015. doi: 10.1061/(ASCE)CC.1943-5614.0000571 [14] YANG J L, WANG J, WANG Z. Behavior and modeling of CFRP nonuniformly wrapped circular seawater sea-sand concrete (SSC) columns under axial compression[J]. Construction and Building Materials,2021,299:123887. doi: 10.1016/j.conbuildmat.2021.123887 [15] LI P, YANG T, ZENG Q, et al. Axial stress-strain behavior of carbon FRP-confined seawater sea-sand recycled aggregate concrete square columns with different corner radii[J]. Composite Structures,2021,262:113589. doi: 10.1016/j.compstruct.2021.113589 [16] YANG J, LU S, WANG J, et al. Behavior of CFRP partially wrapped square seawater sea-sand concrete columns under axial compression[J]. Engineering Structures,2020,222:111119. doi: 10.1016/j.engstruct.2020.111119 [17] ASTM. Standard test method for tensile properties of polymer matrix composite materials: ASTM D3039/D3039M[S]. West Conshonocken: ASTM, 2017. [18] SHEIKH S, UZUMERI S. Strength and ductility of tied concrete columns[J]. Journal of the Structural Division,1980,106(5):1079-1102. doi: 10.1061/JSDEAG.0005416 [19] WEI Y Y, WU Y F. Unified stress-strain model of concrete for FRP-confined columns[J]. Construction and Building Materials,2012,26(1):381-392. doi: 10.1016/j.conbuildmat.2011.06.037 [20] LAM L, TENG J G. Design-oriented stress-strain model for FRP-confined concrete in rectangular columns[J]. Journal of Reinforced Plastics and Composites,2003,22(13):1149-1186. doi: 10.1177/0731684403035429 [21] MAI A D, SHEIKH M N, YAMAKADO K, et al. Nonuniform CFRP wrapping to prevent sudden failure of FRP confined square RC columns[J]. Journal of Composites for Construction,2020,24(6):04020063. doi: 10.1061/(ASCE)CC.1943-5614.0001077 [22] TRIANTAFILLOU T, MATTHYS S, AUDENAERT K. Externally bonded FRP reinforcement for RC structures[M]. Lausanne: International Federation for Structural Concrete, 2001. [23] HARAJLI M H, HANTOUCHE E, SOUDKI K. Stress-strain model for fiber-reinforced polymer jacketed concrete columns[J]. ACI Structural Journal,2006,103(5):672-682. [24] YOUSSEF M N, FENG M Q, MOSALLAM A S. Stress-strain model for concrete confined by FRP composites[J]. Composites Part B: Engineering,2007,38(5):614-628. [25] LIM J C, OZBAKKALOGLU T. Design model for FRP-confined normal-and high-strength concrete square and rectangular columns[J]. Magazine of Concrete Research,2014,66(20):1020-1035. doi: 10.1680/macr.14.00059 [26] GUO Y C, XIAO S H, LUO J W, et al. Confined concrete in fiber-reinforced polymer partially wrapped square columns: Axial compressive behavior and strain distributions by a particle image velocimetry sensing technique[J]. Sensors,2018,18(12):4418. doi: 10.3390/s18124418