Shear Bearing Capacity of Ultra-High Performance Concrete Keyed Joints Based on Shear-Compression Strength Criterion
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摘要:
为探明超高性能混凝土(UHPC)键齿接缝的抗剪承载力及其计算方法,以接缝类型、侧压应力为参数开展5个UHPC键齿接缝和1个UHPC平接缝的足尺模型试验,研究UHPC接缝试件的破坏模式和抗剪承载力变化规律;基于混凝土剪压强度准则,采用八面体应力公式推导UHPC键齿接缝的抗剪承载力计算公式,并与试验结果进行对比验证;通过收集62个UHPC键齿接缝的已有试验数据,对本文所提的计算公式进行精度分析. 研究结果表明:UHPC键齿接缝因键齿根部出现竖向贯通主裂缝而破坏,具有明显的脆性特征;在相同侧压应力下,胶接缝试件的极限荷载比干接缝大21.3%,当侧压应力由3 MPa增大至12 MPa时,胶接缝试件的极限荷载增大了26.9%;本文计算公式可较准确地预测UHPC键齿接缝的抗剪承载力,且离散性较低,计算结果总体偏保守,其中本文5个键齿接缝试件的平均绝对误差为11%,62个已有试件的平均绝对误差为21%.
Abstract:To find out the shear bearing capacity and its calculation method of ultra-high performance concrete (UHPC) keyed joints, a full-scale model test of five UHPC keyed joints and a UHPC flat joint were carried out with the joint type and lateral compressive stress as parameters. The failure mode and the variation of shear bearing capacity of the specimens with UHPC joint were studied. Then, based on the shear-compression strength criterion of concrete, the octahedral stress formula was used to derive the formula for calculating the shear bearing capacity of UHPC keyed joints, which was then validated by the test results. Finally, the experimental data of 62 UHPC keyed joints were collected and used to verify the accuracy of the developed formula. The results show that the UHPC keyed joint is damaged by vertical major cracks developed at the root of the keys and has obvious brittle characteristics. The ultimate load of the specimen with an epoxied joint is greater than that with a dry joint by 21.3% under the same lateral compressive stress. When the lateral compressive stress increases from 3 MPa to 12 MPa, the ultimate load of the specimen with an epoxied joint increases by 26.9%. The developed formula can accurately predict the shear bearing capacity of UHPC keyed joints with low dispersion and conservative results in general. The average absolute errors of the specimen with five keyed joints are 11%, and those of 62 existing specimens are 21%.
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表 1 试件参数
Table 1. Specimen parameters
试件
编号接缝
类型设计侧压
应力/MPa实际侧压
应力/MPa预估承
载力/kNF3-P 平接缝 3 3.13 86.40 F3-G 干接缝 3 3.05 263.17 F3-J 胶接缝 3 2.99 526.40 F6-J 胶接缝 6 6.05 589.53 F9-J 胶接缝 9 9.01 646.66 F12-J 胶接缝 12 12.04 698.57 表 2 试件抗剪承载力对比
Table 2. Comparison of shear bearing capacity of specimens
试件编号 Vt /kN Vc /kN λ $ \overline \lambda $ Sλ λcov F3-G 623.7 657.1 1.05 1.09 0.11 0.10 F3-J 756.3 714.7 0.94 F6-J 836.8 880.3 1.05 F9-J 927.6 1045.9 1.13 F12-J 960.1 1211.5 1.26 表 3 参数分析结果
Table 3. Analysis results of influencing parameters
影响参数 试件数量/个 $ \overline \lambda $ Sλ λcov 键齿数量 单键齿 35 0.92 0.20 0.25 多键齿 27 1.08 0.21 0.25 接缝形式 干接缝 38 0.96 0.18 0.22 胶接缝 24 1.03 0.25 0.31 约束应力比 <1% 9 0.93 0.15 0.16 1%~2% 13 0.89 0.24 0.27 2%~5% 16 0.87 0.17 0.20 5%~10% 15 1.09 0.19 0.21 >10% 10 1.22 0.29 0.25 -
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