Axial Compression Performance of Concrete Columns Confined by Ultra-High Performance Concrete Reinforced with High-Strength Steel Wire Cloth
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摘要:
为掌握新型高强钢丝布增强超高性能混凝土(UHPC)的约束效应,研究高强钢丝布面密度和层数变化对约束混凝土柱轴压性能的影响规律. 首先,利用混凝土泊松比、延性指数和韧性指数对高强钢丝布增强UHPC的约束效应进行评估;其次,考虑高强钢丝布与UHPC提供的约束力,建立复合约束层的侧向约束力模型;最后,基于Ottosen破坏准则和有效约束指标,建立约束混凝土轴压本构模型. 研究结果表明:约束柱受压时呈明显的延性破坏,高强钢丝布增强UHPC约束体系可有效抑制裂缝发展,减缓加载后期试件刚度退化;与未约束柱相比,约束柱的极限承载力、峰值压应变和峰值应力的最大增幅分别为147%、104%和58%;当高强钢丝布层数从1层增加至2层,面密度增加至3.3倍时,约束柱极限承载力、峰值压应变和峰值应力分别提高了8.4%、29.3%和15.8%,延性指数和韧性指数分别提高了50.3%和44.2%. 对比经典约束混凝土轴压本构模型,本文建立的模型与试验结果吻合度较高.
Abstract:In order to master the constraint effect of new high-strength steel wire cloth reinforced ultra-high performance concrete (UHPC), a study was conducted on the influence of the surface density and number of layers of high-strength steel wire cloth on the axial compression performance of confined concrete columns. Firstly, the constraint effect of high-strength steel wire cloth reinforced UHPC was evaluated using Poisson’s ratio, ductility index, and toughness index. Secondly, a lateral constraining force model of the composite constraining layer was established considering the constraining force provided by high-strength steel wire cloth and UHPC. Finally, a constitutive model of axial compression of confined concrete was established based on the Ottosen failure criterion and an effective constraint index. The results show that the confined column exhibits obvious ductile failure under compression, and the high-strength steel wire cloth reinforced UHPC confinement system can effectively suppress crack development and slow down the stiffness degradation of the specimen in the later stage of loading. Compared with the unconfined column, confined columns have maximum increases of 147%, 104%, and 58% in ultimate bearing capacity, peak compressive strain, and peak stress, respectively. When the number of layers of high-strength steel wire cloth increases from 1 to 2, and the surface density increases to 3.3 times, the ultimate bearing capacity, peak compressive strain, and peak stress of the confined column increase by 8.4%, 29.3%, and 15.8%, respectively, while the ductility index and toughness index increase by 50.3% and 44.2%, respectively. The model established in this paper highly agrees with the experimental results compared with the classical constitutive model of axial compression of confined concrete.
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表 1 HSWU混凝土柱设计参数
Table 1. Design parameters of HSWU concrete columns
组号 试件编号 面密度/(g·m−2) 1 G600S1 600 G600S2 600 2 G1200S1 1200 G1200S2 1200 3 G2000S1 2000 G2000S2 2000 4 G0S0 表 2 UHPC配合比
Table 2. Mix proportions of UHPC
kg/m3 水泥 硅灰 矿粉 砂子/目 玻璃
纤维水 减水剂 (10,20] (20,40] (40,70] 646 108 322 457 303 316 39 172 10 表 3 短纤维性能参数
Table 3. Performance parameters of the short fiber
纤维种类 长度/
mm抗拉强
度/MPa密度/
(kg·m−3)弹性模
量/GPa直径/
mm玻璃纤维 18 1700 2600 72 0.014 表 4 混凝土抗压试验结果平均值
Table 4. Average value of concrete compression test results
混凝土强度 fcu/MPa fco/MPa Ec/GPa C60 60.8 39.8 35.8 表 5 UHPC抗压、抗拉试验结果平均值
Table 5. Average value of UHPC compression and tensile test results
fcu,u/MPa fco,u/MPa Eu/GPa ft,u/MPa εtu,max/% 113.2 84.07 40.1 6.85 0.18 表 6 HSWU约束混凝土柱延性指数和韧性指数
Table 6. Ductility index and toughness index of HSWU restrained concrete columns
试件编号 延性指数 韧性指数 G0S0 G600S1 5.81 0.52 G600S2 6.32 0.65 G1200S1 7.17 0.69 G1200S2 8.41 0.73 G2000S1 7.69 0.71 G2000S2 8.73 0.75 表 7 HSWU约束混凝土柱轴压试验试验结果
Table 7. Axial compression test results of HSWU restrained concrete columns
试件编号 Fmax(F0)/kN Fmax/F0 εcu(εco) εcu/εco εtu fcc/MPa fcc/fco εcc ε70 G0S0 1130 0.0026 G600S1 2576 2.28 0.0041 1.58 0.0034 54.27 1.36 0.0046 0.0065 G600S2 2641 2.34 0.0047 1.81 0.0035 57.07 1.43 0.0049 0.0083 G1200S1 2595 2.30 0.0043 1.65 0.0034 56.85 1.43 0.0048 0.0091 G1200S2 2743 2.43 0.0052 2.00 0.0037 61.36 1.54 0.0057 0.0145 G2000S1 2617 2.32 0.0044 1.69 0.0035 57.64 1.45 0.0051 0.0119 G2000S2 2792 2.47 0.0053 2.04 0.0037 62.85 1.58 0.0063 0.0183 注:F0和εco分别为未约束试件峰值荷载和峰值轴向应变,εtu为约束试件峰值荷载时的横向应变,fcc和εcc分别为HSWU约束混凝土核心区峰值应力和峰值应变,ε70为HSWU约束混凝土核心区峰值应力下降30%时所对应的轴向应变. -
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