Experimental study on seismic performance of polyvinyl alcohol fiber reinforced cementitious composite medium-length columns with low axial pressure ratio
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摘要: 已有对聚乙烯醇纤维增强水泥基复合材料(PVA/C)柱抗震性能的研究大多针对短柱,且PVA/C一般只在节点及其邻近部位局部设置。基于此,本文对低轴压比且沿柱全高设置的PVA/C中长柱进行低周反复荷载试验,变化参数为纤维体积分数ρf和体积配箍率ρv。通过试验,得出以下结论:所有试件均发生弯曲破坏;当ρf和ρv分别在试验设计范围内增大时,试件的裂缝控制能力、延性、截面转动能力及耗能能力均提高,刚度退化及承载力衰减速度减小;ρf的增大可较大程度提高试件开裂荷载,而对峰值荷载影响较小;ρf由0 vol%提高到2 vol%,位移延性系数、耗能比及开裂荷载分别提高52.9%、112.3%和51.1%;掺加适量纤维后,即使降低配箍率,试件也可保持良好的抗震性能和裂缝形态。根据本文试验数据并收集其他相关文献试验数据,拟合得出位移延性系数与ρf和ρv之间的关系式。最后总结了各类PVA/C柱抗震性能差异。Abstract: Previous studies on the seismic performance of polyvinyl alcohol fiber reinforced cementitious compo-site (PVA/C) columns mostly focused on short columns, and PVA/C was usually set locally in the joint and its adjacent parts. Based on this, low-cycle reversed loading tests on medium-length PVA/C columns with low axial pressure ratio were carried out, and PVA/C was set along the full height of the column. Test variation parameters are fiber volume fraction ρf and volume-stirrup ratio ρv. The following conclusions can be drawn through the test: Bending failure occurs in all specimens. When ρf and ρv increase within the test condition range respectively, the crack controlling ability, ductility, section rotation ability and energy dissipation ability of specimens are improved. While the rate of stiffness degradation and decay of bearing capacity are decreased. The increase of ρf can greatly improve the cracking load of specimens, but has little effect on the peak load. When ρf increases from 0 vol% to 2 vol%, the displacement ductility coefficient, the energy consumption ratio and the cracking load increase 52.9%, 112.3% and 51.1%, respectively. The PVA/C columns can maintain good seismic performance and crack morphology even if the stirrup ratio is reduced. According to the experimental data of this paper and other relevant literature, the relationship between displacement ductility coefficient and ρf and ρv is obtained. Differences of seismic performance of various PVA/C columns were summarized.
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表 1 试验工况
Table 1. Test conditions
Specimen Fiber volume
fraction
$ \rho _{\rm{f}} $/vol%Designed axial
compression
ratio nText axial
compression ratio ntShear
span
ratioRebar Stirrup Stirrup volume
ratio $ \rho _{\rm{v}} $/%0vol%PVA/C-70 0 0.3 0.179 5.5 4 12 Φ8@70 1.74 1vol%PVA/C-70 1.0 0.3 0.179 5.5 4 12 Φ8@70 1.74 2vol%PVA/C-70 2.0 0.3 0.179 5.5 4 12 Φ8@70 1.74 1vol%PVA/C-100 1.0 0.3 0.179 5.5 4 12 Φ8@100 1.22 1vol%PVA/C-130 1.0 0.3 0.179 5.5 4 12 Φ8@130 0.94 Note: PVA/C—Polyvinyl alcohol fiber reinforced cementitious composite. 表 2 PVA/C配合比
Table 2. Mix proportion of PVA/C
Cement Fly ash Water Sand Thickener/% Defoamer/% Plasticizer/% Fiber content/vol% 0.8 0.2 0.5 0.8 0.05 1 0.1 0, 1, 2 Notes: Fiber content—Volume fraction, other materials are mass ratio; Water/cement mass ratio is 0.5. 表 3 PVA纤维性能
Table 3. Properties of PVA fiber
Fineness/dtex Density/(g·cm−3) Diameter/mm Elongation/% Length/mm Tensile strength/MPa Elastic modulus/GPa 15 1.3 0.04 6 12 1600 40 表 4 钢筋受拉力学性能参数
Table 4. Tensile mechanical properties of rebar
Steel grade Diameter/mm Yield strength/MPa Ultimate strength/MPa Elongation after fracture/% HRB400 12 442 635 25.0 16 449 640 23.0 20 450 640 22.5 表 5 PVA/C材料力学性能
Table 5. Mechanical properties of PVA/C
Fiber content/vol% fcu/MPa fc/MPa ft/MPa 0 46.63 42.66 2.25 1 46.31 41.18 4.70 2 46.12 40.81 5.08 Notes: fcu—Cube crushing strength; fc—Prism compressive strength; ft—Axial tensile strength. 表 6 PVA/C试件特征值
Table 6. Characteristic values of PVA/C specimens
Specimen Loading direction Cracking point Yield point Peak point Ultimate point Pcr/kN $\varDelta _{\rm{cr}}$/mm Py/kN $\varDelta_{\rm{y}}$/mm Pm/kN $\varDelta_{\rm{m}}$/mm Pu/mm $\varDelta_{\rm{u}}$/mm 0vol%PVA/C-70 Positive direction 6.60 1.86 24.20 16.43 29.40 22.24 14.95 51.00 Negative direction −11.2 −0.29 −38.30 −14.83 −43.40 −23.45 −36.90 −50.54 1vol%PVA/C-70 Positive direction 17.60 3.41 26.70 11.38 31.70 22.7 13.66 59.04 Negative direction −9.60 −0.84 −37.70 −14.44 −45.40 −24.31 −38.60 −60.39 2vol%PVA/C-70 Positive direction 17.50 3.40 25.50 11.31 31.10 25.19 18.40 68.92 Negative direction −9.40 −1.43 −33.70 −18.20 −41.00 −27.06 −34.90 −77.73 1vol%PVA/C-100 Positive direction 11.80 2.57 26.20 10.40 30.60 22.06 17.36 46.06 Negative direction −11.80 −1.56 −38.1 −12.44 −45.10 −23.12 −38.30 −44.15 1vol%PVA/C-130 Positive direction 10.00 2.74 25.40 11.89 29.10 18.65 16.06 43.00 Negative direction −13.30 −1.44 −32.20 −10.16 −39.50 −25.39 −33.60 −41.04 Notes: Pcr—Column cracking load; $\varDelta _{\rm{cr}}$—Column cracking displacement; Py—Yield load of longitudinal reinforcement; $\varDelta_{\rm{y}}$—Specimen yield displacement; Pm—Peak load; $\varDelta_{\rm{m}}$—Displacement when the column reached peak load; Pu—Loads of specimens in both positive and negative directions decreased to 85% of peak load; $\varDelta_{\rm{u}}$—Displacement when the column reached ultimate load. 表 7 PVA/C试件位移参数汇总
Table 7. Summary of displacement parameters of PVA/C specimens
Specimen Yield displacement $ {\varDelta}_{\rm{y}} $/mm Ultimate displacement $ {\varDelta}_{\rm{u}} $/mm Displacement ductility coefficient ${{\mu }}$ Elastic-plastic limit displacement angle $\mathop \theta \nolimits_{\rm{u}} $ Absolute value Relative value Absolute value Relative value 0vol%PVA/C-70 15.63 50.77 3.25 1 1/22 1 1vol%PVA/C-70 12.91 59.72 4.63 1.42 1/19 1.16 2vol%PVA/C-70 14.76 73.33 4.97 1.53 1/15 1.47 1vol%PVA/C-100 11.42 45.11 3.95 1.22 1/24 0.92 1vol%PVA/C-130 11.03 42.02 3.81 1.17 1/26 0.85 表 8 PVA/C位移延性系数试验结果与计算结果对比
Table 8. Comparison between test results and calculated values of displacement ductility coefficient of PVA/C
Specimen Test value ${{\mu }_{\rm{e}}}$ Calculated value ${{\mu }_{\rm{c}}}$ ${{{{\mu }_{\rm{c}}}} / {{{\mu }_{\rm{e}}}}}$ 1vol%PVA/C-70 4.63 4.63 1.00 2vol%PVA/C-70 4.97 5.10 0.97 1vol%PVA/C-100 3.95 2.60 1.52 1vol%PVA/C-130 3.81 4.39 0.87 R/FRC3[10] 3.44 3.39 1.01 R/FRC4[10] 3.35 3.39 0.99 R/FRC5[10] 3.58 3.21 1.11 R/FRC6[10] 3.48 3.21 1.08 S1[19] 3.11 3.80 0.82 S3[19] 3.71 3.80 0.98 S6[20] 6.09 5.54 1.09 S7[20] 5.15 5.39 0.96 表 9 PVA/C曲率计算值
Table 9. Curvature calculation values of PVA/C
Specimen Yield curvature $\mathop {\varphi }\nolimits_{\rm{y}} $ Relative yield curvature Peak curvature $\mathop \varphi \nolimits_{\rm{p}} $ Relative peak curvature 0vol%PVA/C-70 2.71×10−5 1.00 3.43×10−5 1.00 1vol%PVA/C-70 3.05×10−5 1.13 4.68×10−5 1.36 2vol%PVA/C-70 3.26×10−5 1.20 4.89×10−5 1.43 1vol%PVA/C-100 2.99×10−5 1.10 4.36×10−5 1.27 1vol%PVA/C-130 2.39×10−5 0.88 3.36×10−5 0.98 -
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