Mechanical behavior of bamboo scrimber filled steel tube under different loading modes
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摘要: 本文将重组竹与钢管复合形成新型钢管约束重组竹。对24个新型钢管约束重组竹圆柱试件进行了轴压试验,研究了钢管厚度和加载方式(全截面与核心加载)对其轴压性能的影响。试验结果表明:外加钢管能够有效地提高结构承载力和变形能力;钢管约束重组竹圆柱主要破坏形态为剪切破坏;结构的峰值应力、峰值应变均与钢管厚度呈正相关,随着钢管厚度增加,试件的峰值应力最大增长22.4%,峰值应变最大增长6.1%;核心受压钢管重组竹较全截面受压试件展现了更好的承载潜力和变形能力。根据全截面受压和核心受压的曲线不同,考虑了钢管套箍系数,分别提出了两种加载方式下新型钢管约束重组竹的极限应力、极限应变和峰值应力、峰值应变的预测模型,应力计算模型误差均在10%以内。最后建议了应力-应变全曲线模型,预测了不同加载方式下新型钢管约束重组竹的应力-应变变化规律。Abstract: By means of structural innovation, a new type of bamboo scrimber filled steel tube was formed by composite materials of bamboo scrimber and steel tube. Axial compression tests were carried out on 24 cylindrical specimens of the new type of bamboo scrimber filled steel tube to study the effect of steel tube thickness and loading mode (full section and core loading) on its axial compression performance. The test results show that the external steel tube can effectively improve the structural bearing capacity and deformation capacity, and the main failure mode of the bamboo scrimber filled steel tube is shear failure. The peak stress and peak strain of the structure are positively correlated with the steel tube thickness. As the steel tube thickness increases, the maximum increase in peak stress of the specimens reaches 22.4%, while the maximum increase in peak strain is 6.1%. The core loading specimens exhibit better load bearing potential and deformation capacity than the full section loading specimens. Based on the different curves of full section loading and core loading, and considering the steel tube confinement factor, the prediction models of ultimate stress, ultimate strain, peak stress and peak strain of the new type of bamboo scrimber filled steel tube under different loading modes are proposed, and the error of the stress calculation model is less than 10%. Finally, the stress-strain full curve model is proposed, and the stress-strain variation of the new bamboo scrimber filled steel tube under different loading modes is predicted.
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图 7 不同钢管厚度钢管重组竹应力-应变曲线对比
Figure 7. Comparisons of stress-strain curves of bamboo scrimber filled steel tube with different steel tube thickness
fc—Peak stress of bamboo scrimber filled steel tube specimen; fc0—Ultimate stress of the bamboo scrimber; εc0—Ultimate strain of the bamboo scrimber; εc—Peak strain of bamboo scrimber filled steel tube specimen
表 1 钢管约束重组竹柱轴压试验结果
Table 1. Axial compression test result of bamboo scrimber filled steel tube
Specimen H/mm Db/mm Ds/mm Pcu/kN fce/MPa εce fcy/MPa εcy fcc/MPa εcc Ebs/GPa D1S4.5-F 345 103 114 1628.8 92.56 0.0019 — — 159.58 0.064 44.5 D1S6.0-F 345 100 114 1994.2 113.32 0.0021 — — 195.37 0.063 52.3 D2S4.5-F 400 122 133 1882.3 78.58 0.0019 — — 135.49 0.063 42.1 D2S6.0-F 400 119 133 2292.6 95.71 0.0018 — — 165.02 0.065 43.8 D1S4.5-C 345 103 114 1412.0 — — 142.78 0.033 169.46 0.086 15.8 D1S6.0-C 345 100 114 1413.2 — — 162.90 0.047 179.94 0.087 16.2 D2S4.5-C 400 122 133 1630.3 — — 122.86 0.033 139.46 0.075 16.7 D2S6.0-C 400 119 133 1674.3 — — 131.55 0.031 150.54 0.075 15.2 Notes: Specimens were numbered according to the different parameters of the specimens; D—Diameter of specimen; S—Thickness of the steel tube; F—Full section loading; C—Core loading; H—Height of all specimens; Db—Diameter of bamboo scrimber; Ds—Outer diameter of steel tube; Pcu—Peak load; fce—Proportional limit stress; εce—Proportional limit strain; fcy—Yield stress; εcy—Yield strain; fcc—Peak stress; εcc—Peak strain; Ebs—Nominal initial compressive elastic modulus. 表 2 钢管力学性能指标
Table 2. Mechanical properties of steel tube
Ds/mm ts/mm fy/MPa fu/MPa Es/GPa 114 4.5 327.4 465.9 205.2 133 4.5 336.8 502.2 206.1 114 6.0 376.0 510.2 206.4 133 6.0 381.2 499.2 205.1 Notes: ts—Thickness of steel tube; fy—Yield strength of steel tube; fu—Ultimate tensile strength of steel tube; Es—Elastic modulus of steel tube. 表 3 重组竹试件力学性能指标
Table 3. Properties of bamboo scrimber
Specimen H/mm Db/mm Pbu/kN fby/MPa εby fbu/MPa εbu Eb/GPa D103 345 103 823.8 95.41 0.029 98.87 0.050 18.6 D100 345 100 767.0 94.24 0.029 97.66 0.050 15.6 D122 400 122 1121.9 92.61 0.028 95.97 0.052 15.0 D119 400 119 1053.4 91.40 0.026 94.71 0.048 14.8 Notes: Pbu—Ultimate load; fby—Yield stress of the bamboo scrimber; εby—Yield strain of the bamboo scrimber; fbu—Ultimate stress of the bamboo scrimber; εbu—Ultimate strain of the bamboo scrimber; Eb—Initial compressive elastic modulus. -
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