Axial ultimate compressive stress model of BFRP-confined rectangular concrete based on tensile strain at rounded corners
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摘要: 对54个玄武岩纤维增强树脂基复合材料(BFRP)约束的矩形截面混凝土试件进行了轴压试验,探究了BFRP约束层数、倒角半径和截面长宽比对BFRP拉应变折减系数的影响规律。试验结果表明,依据矩形截面侧边拉应变和环向平均拉应变确定的BFRP拉应变折减系数会高估BFRP的约束效率。基于BFRP约束矩形截面混凝土时倒角处的纤维拉应变,建议了BFRP拉应变折减系数的计算方法,同时依据该计算方法和试验数据,通过构建柱状膜结构静水压力平衡模型建立了BFRP约束矩形截面混凝土轴压峰值应力计算模型。基于收集的大量试验数据,对比分析了本文建议的纤维增强树脂基复合材料(FRP)约束矩形截面混凝土轴压峰值应力计算模型和典型轴压峰值应力计算模型的预测结果,验证了典型计算模型的合理性,发现本文建议的FRP约束矩形截面混凝土轴压峰值应力计算模型的预测精度较高。Abstract: This paper presents an experimental study on the axial compressive behavior of 54 rectangular prisms confined with basalt fiber-reinforced polymer (BFRP). The influences of the BFRP layers, corner radius and aspect ratio on the tensile strain reduction factors of BFRP were investigated. The test results show that the tensile strain reduction factors calculated based on tensile strains in sides and average tensile strain of lateral BFRP sheets will overestimate confinement efficiency. Based on tensile strains at the corners, a computing method of tensile strain reduction factors of BFRP sheets was proposed. According to the proposed computing method of tensile strain reduction factors and experimental data in this paper, the hydrostatic pressure balance equation of the cylindrical BFRP membrane was used to build an axial ultimate compressive stress model of BFRP-confined rectangular concrete. Based on a large collection of test data, predicted results of the proposed model and the existing typical models were compared and analyzed. The rationality of the existing typical models was verified. The prediction accuracy of the proposed axial ultimate compressive stress model is higher than the existing typical models.
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Key words:
- basalt fiber /
- concrete /
- axial compressive behavior /
- ultimate stress /
- tensile strain reduction factor
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表 1 试件基本参数
Table 1. Details of specimens
Corner radius/mm Number of confinement layer Section dimension/mm (Aspect ratio) 100×100 (1.0) 83×124.5 (1.5) 75×150 (2.0) 20 3 A10 R20 L3-1 A15 R20 L3-1 A20 R20 L3-1 A10 R20 L3-2 A15 R20 L3-2 A20 R20 L3-2 A10 R20 L3-3 A15 R20 L3-3 A20 R20 L3-3 4 A10 R20 L4-1 A15 R20 L4-1 A20 R20 L4-1 A10 R20 L4-2 A15 R20 L4-2 A20 R20 L4-2 A10 R20 L4-3 A15 R20 L4-3 A20 R20 L4-3 5 A10 R20 L5-1 A15 R20 L5-1 A20 R20 L5-1 A10 R20 L5-2 A15 R20 L5-2 A20 R20 L5-2 A10 R20 L5-3 A15 R20 L5-3 A20 R20 L5-3 30 3 A10 R30 L3-1 A15 R30 L3-1 A20 R30 L3-1 A10 R30 L3-2 A15 R30 L3-2 A20 R30 L3-2 A10 R30 L3-3 A15 R30 L3-3 A20 R30 L3-3 4 A10 R30 L4-1 A15 R30 L4-1 A20 R30 L4-1 A10 R30 L4-2 A15 R30 L4-2 A20 R30 L4-2 A10 R30 L4-3 A15 R30 L4-3 A20 R30 L4-3 5 A10 R30 L5-1 A15 R30 L5-1 A20 R30 L5-1 A10 R30 L5-2 A15 R30 L5-2 A20 R30 L5-2 A10 R30 L5-3 A15 R30 L5-3 A20 R30 L5-3 Notes:Number following letter A represents aspect ratio; Number following letter R represents corner radius; Number following letter L represents FRP layers; The last number represents sequence number of specimens with same condition. 表 2 BFRP力学性能
Table 2. Mechanical properties of BFRP
Type Ultimate tensile stress/MPa Elastic modulus/GPa Ultimate tensile strain/% Thickness
/mmDensity
/(g·m−2)BF3300 2303 105 2.18 0.121 341 表 3 混凝土配合比
Table 3. Proportions of concrete mix
Strength grade of concrete Sand ratio Amount of each composition/(kg·m−3) Cement Gravel Sand Water C40 0.32 451 1206 568 185 表 4 BFRP约束矩形截面混凝土轴压试验结果
Table 4. Test results of rectangular sections concrete confined with BFRP
Specimen fcc/MPa εcu R1 T1 M1 M2 T2 R2 εh,max A10 R20 L3-1 61.72 0.01416 – 0.02074 0.01657 0.01678 0.01753 0.01417 0.02074 A10 R20 L3-2 60.03 0.01348 0.01352 0.01731 0.01744 0.01679 0.01731 0.01308 0.01744 A10 R20 L3-3 60.23 0.01368 0.01352 0.01709 0.01635 – 0.01043 0.01330 0.01709 A10 R20 L4-1 69.15 0.01654 – 0.01992 0.01591 0.01635 0.01788 0.01308 0.01992 A10 R20 L4-2 71.60 0.01923 0.01308 0.01709 0.01679 0.01657 0.01809 0.01373 0.01809 A10 R20 L4-3 67.18 0.01586 0.01264 – 0.01635 0.01613 0.01788 0.01308 0.01788 A10 R20 L5-1 79.02 0.02265 0.01308 0.01684 0.01635 0.01613 – 0.01330 0.01684 A10 R20 L5-2 78.55 0.02024 0.01264 0.01666 0.01591 0.01570 0.01688 0.01243 0.01688 A10 R20 L5-3 77.93 0.01944 0.01221 0.01644 0.01548 – 0.01666 0.01221 0.01666 A10 R30 L3-1 65.44 0.01511 0.01395 0.01709 – 0.01657 0.01731 0.01373 0.01731 A10 R30 L3-2 66.18 0.01612 0.01439 0.01753 0.01722 0.01766 0.02071 – 0.02071 A10 R30 L3-3 65.91 0.01551 0.01352 0.01731 0.01679 0.01679 0.01731 0.01417 0.01731 A10 R30 L4-1 77.79 0.01991 0.01373 0.01709 0.01635 0.01635 0.01734 0.01308 0.01734 A10 R30 L4-2 76.57 0.01865 0.01330 0.01688 0.01657 0.01613 0.01709 0.01373 0.01709 A10 R30 L4-3 78.57 0.02043 - 0.02017 0.01679 0.01722 0.01784 0.01373 0.02017 A10 R30 L5-1 87.43 0.02315 0.01264 – 0.01570 0.01591 0.01662 0.01308 0.01662 A10 R30 L5-2 87.81 0.02394 0.01308 0.01709 0.01657 0.01657 – 0.01352 0.01709 A10 R30 L5-3 86.92 0.02324 0.01286 0.01667 0.01613 0.01591 0.01666 0.01330 0.01667 A15 R20 L3-1 53.64 0.01186 0.01134 0.01453 0.01384 0.01809 0.01853 0.01155 0.01853 A15 R20 L3-2 53.47 0.01153 – 0.00050 0.01384 0.01788 0.01831 0.01134 0.01831 A15 R20 L3-3 51.94 0.01099 – 0.00513 0.01367 0.01766 0.01809 0.01112 0.01809 A15 R20 L4-1 60.96 0.01394 0.01112 0.01385 0.01341 0.01744 0.01833 0.01090 0.01833 A15 R20 L4-2 61.73 0.01426 0.01134 0.01509 0.01363 0.01766 0.01809 – 0.01809 A15 R20 L4-3 60.20 0.01387 0.01090 0.01466 0.01319 0.01722 0.01788 0.01046 0.01788 A15 R20 L5-1 67.11 0.01661 0.01068 0.01365 0.01297 0.01657 0.01744 0.01090 0.01744 A15 R20 L5-2 66.27 0.01623 0.01003 0.01344 0.01275 0.01744 0.01788 0.01025 0.01788 A15 R20 L5-3 68.80 0.01696 0.01003 0.01449 0.01319 – 0.01766 0.01090 0.01766 A15 R30 L3-1 60.34 0.01317 0.01330 0.01431 0.01417 – 0.02093 – 0.02093 A15 R30 L3-2 57.97 0.01234 0.01243 0.01388 0.01330 0.01744 0.01809 0.01264 0.01809 A15 R30 L3-3 58.36 0.01283 0.01286 0.01389 – 0.01788 0.01831 0.01308 0.01831 A15 R30 L4-1 67.34 0.01586 0.01177 0.01382 0.01330 0.01722 0.01809 0.01286 0.01809 A15 R30 L4-2 69.45 0.01614 0.01199 0.01409 0.01373 0.01766 0.02071 – 0.02071 A15 R30 L4-3 66.43 0.01531 0.01155 0.01379 0.01286 0.01679 – 0.01243 0.01679 A15 R30 L5-1 74.62 0.01852 0.01068 0.01343 0.01264 0.01657 0.02093 – 0.02093 A15 R30 L5-2 75.07 0.01886 0.01155 0.01365 0.01286 0.01679 0.01744 0.01199 0.01744 A15 R30 L5-3 76.57 0.01899 0.01177 – 0.01308 0.01700 0.01766 0.01243 0.01766 A20 R20 L3-1 46.78 0.00916 0.00850 0.01309 0.01210 – – 0.00828 0.01309 A20 R20 L3-2 47.81 0.01013 0.00916 0.01331 0.01232 0.02027 0.01831 0.00872 0.02027 A20 R20 L3-3 47.90 0.01016 0.00916 0.01331 0.01254 0.01984 0.02071 – 0.02071 A20 R20 L4-1 55.54 0.01211 0.00850 0.01309 0.01210 0.02006 0.02049 – 0.02049 A20 R20 L4-2 52.03 0.01123 0.00763 0.01309 0.01166 0.01918 0.01809 0.00828 0.01918 A20 R20 L4-3 52.44 0.01169 – 0.02027 0.01188 0.01962 0.01809 0.00872 0.02027 A20 R20 L5-1 58.08 0.01331 0.00719 – 0.01101 0.01875 0.01831 0.00763 0.01875 A20 R20 L5-2 58.98 0.01353 0.00763 0.01231 – 0.01962 0.02115 – 0.02115 A20 R20 L5-3 59.28 0.01389 0.00807 0.01253 0.01188 – 0.01875 0.00850 0.01875 A20 R30 L3-1 50.90 0.01055 0.01068 0.01253 0.01247 – 0.01809 0.01112 0.01809 A20 R30 L3-2 52.16 0.01123 – 0.02049 0.01269 0.02049 0.01875 0.01134 0.02049 A20 R30 L3-3 50.09 0.01014 0.01068 0.01231 0.01225 0.02006 0.01862 0.01090 0.02006 A20 R30 L4-1 58.47 0.01316 0.01046 0.01209 0.01225 0.02006 – 0.01090 0.02006 A20 R30 L4-2 57.54 0.01248 0.01003 0.01166 0.01182 0.01962 0.01809 0.01046 0.01962 A20 R30 L4-3 58.08 0.01294 0.01025 0.01388 0.01203 0.01984 0.02093 – 0.02093 A20 R30 L5-1 63.73 0.01467 – 0.02115 0.01094 0.01875 0.01744 0.00894 0.02115 A20 R30 L5-2 68.55 0.01573 0.01025 – 0.01203 0.01984 0.01809 0.01003 0.01984 A20 R30 L5-3 64.73 0.01493 0.01068 0.01166 0.01182 0.01962 0.01766 0.00981 0.01962 Notes: fcc—Ultimate stress; εcu—Ultimate strain; εh,max—Maximal strain of FRP. -
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