Mechanical properties of CFRP bar and bond-type anchorage system after elevated temperature exposure
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摘要: 为明确高温后碳纤维增强树脂复合材料(Carbon fiber reinforced polymer,CFRP)筋材及其粘结型锚固系统的力学性能,以筋材的处理温度为试验参数,完成了12个筋材试件的轴向拉伸试验;以粘结式锚具的处理温度和粘结长度为试验参数,完成了36个试件的锚固性能试验。结果表明:对于筋材轴向拉伸试件,处理温度为100℃时,筋材静力性能与常温试件相比未发生明显变化,筋材经历200℃和300℃温升作用后,其抗拉强度、弹性模量和极限拉应变较常温试件分别下降了6.4%、8.2%、3.8%和16.6%、18.3%、8.3%;对于锚固性能试验,试件的粘结强度随处理温度和粘结长度的增加而降低,粘结长度一定时,处理温度为200℃与300℃试件的粘结强度较常温试件分别下降了31.5%~36.3%和44.2%~47.4%。建立了适于分析高温后CFRP筋轴向拉伸性能、粘结型锚固系统粘结强度及临界锚固长度的实用计算公式,且具较高精度。Abstract: To investigate the mechanical properties of carbon fiber reinforced polymer (CFRP) bar and bond-type anchorage system after different elevated temperature exposures, the axial tensile tests and anchorage perfor-mance tests were conducted on 12 specimens and 36 specimens with different elevated temperatures and bond lengths, respectively. The results demonstrate that the static performance of CFRP bar exposed to elevated temperature of 100℃ degenerates slightly compared with the specimen at room temperature in the axial tensile tests. The tensile strength, elastic modulus and ultimate strain of specimens exposed to the elevated temperature of 200℃ and 300℃ decrease by 6.4%, 8.2%, 3.8% and 16.6%, 18.3%, 8.3%, respectively, compared with the specimen at room temperature. In the anchorage performance tests, the bond strength of the specimens decreases with the increase of elevated temperature and bond length. Compared with the specimen at room temperature, the bond strengths of the specimens exposed to the elevated temperature of 200℃ and 300℃ decrease by 31.5%-36.3% and 44.2%-47.4%, respectively, while the bonding length is fixed. The practical formulas with high accuracy for determining the axial tensile performance of CFRP bars, bond strength and critical anchorage length of the bond-type anchorage system after elevated temperature exposure were developed.
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表 1 CFRP筋外观尺寸及玻璃化转变温度Tg
Table 1. Dimensions and glass transition temperature Tg of CFRP bar
Nominal diameter/mm Rib width/mm Rib height/mm Embossing spacing/mm Tg/℃ 12 9.26 0.27 14.8 211.6 表 2 RPC配合比及抗压强度
Table 2. Mix proportion and compressive strengths of RPC
Strength grade Cement Silica fume Quartz flour Quartz sand Water reducer Water binder ratio Measured strength/MPa RPC150 1 0.25 0.25 1.1 0.02 0.16 158 表 3 CFRP筋-RPC轴向拉伸试验结果
Table 3. Results of axial tensile test for CFRP bar-RPC
Specimen code $\overline{ P_{\rm{u}}}$/kN Pu/kN fu/MPa $ \overline{ f_{\rm{u}}} $/MPa E/GPa $ \overline E $/GPa εu/10−6 $ \overline{\varepsilon _{\rm{u}}} $/10−6 CFRP-RPC-T25-1 280.8 282.8 2631.1 162.2 15627 CFRP-RPC-T25-2 283.1 2652.6 2649.8 161.8 159.9 15464 15513 CFRP-RPC-T25-3 284.5 2665.7 155.6 15448 CFRP-RPC-T100-1 279.9 279.6 2622.6 162.3 15482 CFRP-RPC-T100-2 278.8 2612.3 2619.8 153.6 157.3 15385 15428 CFRP-RPC-T100-3 280.1 2624.5 156.0 15417 CFRP-RPC-T200-1 260.6 264.7 2441.8 151.7 15084 CFRP-RPC-T200-2 269.2 2522.4 2480.2 146.2 146.8 15012 14925 CFRP-RPC-T200-3 264.3 2476.5 142.5 14679 CFRP-RPC-T300-1 242.7 235.8 2274.1 128.4 14285 CFRP-RPC-T300-2 231.4 2168.2 2209.4 133.3 130.7 14364 14232 CFRP-RPC-T300-3 233.3 2186.0 130.4 14047 Notes: Specimen code indicates the test type and treatment temperature; for example, CFRP-RPC-T25-1 means the first specimen of CFRP-RPC anchorage specimen treated at 25℃ in axial tensile test; Pu—Tensile breaking force; $\overline {{P_{\rm{u}}}} $—Average value; $\overline {{f_{\rm{u}}}} $—Average value; E—Elastic modulus; $\overline E $—Average value; εu—Ultimate tensile strain; $\overline {{\varepsilon _{\rm{u}}}} $—Average value. 表 4 CFRP筋-RPC锚固性能试验结果
Table 4. Results of anchorage performance test for CFRP bar-RPC
Specimen code T/
℃l/
mmPu/
kN${\overline {P_{\rm{u}}} }$/
kNτu/
MPas/
mmSpecimen code T/
℃l/
mmPu/
kN${\overline {P_{\rm{u}}}} $/
kNτu/
MPas/
mmCFRP-RPC-T25-L5d-1 25 60 69.3 69.35 30.67 5.42 CFRP-RPC-T200-L5d-1 200 60 41.23 47.53 21.02 5.74 CFRP-RPC-T25-L5d-2 69.45 5.36 CFRP-RPC-T200-L5d-2 48.9 5.68 CFRP-RPC-T25-L5d-3 69.3 5.26 CFRP-RPC-T200-L5d-3 52.45 5.80 CFRP-RPC-T25-L10d-1 25 120 135.3 134.1 29.66 5.52 CFRP-RPC-T200-L10d-1 200 120 85.5 85.46 18.9 5.91 CFRP-RPC-T25-L10d-2 132.9 5.35 CFRP-RPC-T200-L10d-2 81.68 5.98 CFRP-RPC-T25-L10d-3 — — CFRP-RPC-T200-L10d-3 89.2 5.93 CFRP-RPC-T25-L15d-1 25 180 192.4 190.47 28.08 — CFRP-RPC-T200-L15d-1 200 180 118.9 123.57 18.22 — CFRP-RPC-T25-L15d-2 192.7 — CFRP-RPC-T200-L15d-2 131.8 — CFRP-RPC-T25-L15d-3 186.3 — CFRP-RPC-T200-L15d-3 120 — CFRP-RPC-T100-L5d-1 100 60 62.37 61.09 27.02 5.14 CFRP-RPC-T300-L5d-1 300 60 35.92 37.42 16.55 5.68 CFRP-RPC-T100-L5d-2 59.35 5.26 CFRP-RPC-T300-L5d-2 41.98 5.36 CFRP-RPC-T100-L5d-3 61.55 5.37 CFRP-RPC-T300-L5d-3 34.35 5.41 CFRP-RPC-T100-L10d-1 100 120 119.5 118.23 26.15 5.85 CFRP-RPC-T300-L10d-1 300 120 66.23 70.12 15.51 5.73 CFRP-RPC-T100-L10d-2 115.5 5.84 CFRP-RPC-T300-L10d-2 74.9 5.75 CFRP-RPC-T100-L10d-3 119.7 6.73 CFRP-RPC-T300-L10d-3 69.23 5.68 CFRP-RPC-T100-L15d-1 100 180 173.6 173 25.51 — CFRP-RPC-T300-L15d-1 300 180 105.3 100.11 14.76 — CFRP-RPC-T100-L15d-2 174.3 — CFRP-RPC-T300-L15d-2 96.93 — CFRP-RPC-T100-L15d-3 171.1 — CFRP-RPC-T300-L15d-3 98.11 — Notes: Specimen code indicates the test type and treatment temperature; for example, CFRP-RPC-T25-L5d-1 means the first specimen of CFRP-RPC anchorage specimen treated at 25℃ with bond length of 5d; T—Treatment temperature; l—Bond length; τu—Average bond strength; s—Slip of loading end corresponding to Pu. 表 5 CFRP筋-RPC试件粘结强度试验值与计算值对比
Table 5. Comparison between measured and predicted bond strength of CFRP bar-RPC specimen
Specimen code fcu/MPa τu,t/MPa τu,c/MPa τu,t/τu,c CFRP-RPC-T25-L5d 158 30.67 30.97 1.01 CFRP-RPC-T25-L10d 158 29.66 29.06 0.98 CFRP-RPC-T25-L15d 158 28.08 28.42 1.01 CFRP-RPC-T100-L5d 158 27.02 26.91 1.00 CFRP-RPC-T100-L10d 158 26.15 25.25 0.97 CFRP-RPC-T100-L15d 158 25.51 24.70 0.97 CFRP-RPC-T200-L5d 158 21.02 21.49 1.02 CFRP-RPC-T200-L10d 158 18.9 20.17 1.07 CFRP-RPC-T200-L15d 158 18.22 19.72 1.08 CFRP-RPC-T300-L5d 158 16.55 16.08 0.97 CFRP-RPC-T300-L10d 158 15.51 15.08 0.97 CFRP-RPC-T300-L15d 158 14.76 14.75 1.00 Average 1.00 Variation coefficient 0.04 Notes: fcu—Cube compressive strength of RPC; τu,t, τu,c—Experimental and calculated values of interfacial bond strength between CFRP bars and RPC, respectively. 表 6 CFRP筋-RPC试件临界锚固长度计算值及预测的破坏形态
Table 6. Critical anchorage length determined by formula and predicted failure mode of CFRP bar-RPC specimen
Source of
test resultsSpecimen code T/℃ Anchorage
length/mmActua failure
modeCritical anchorage
length/mmPredicted
failure modePresent study CFRP-RPC-T25 25 360 Fracture 284.4 Fracture CFRP-RPC-T100 CFRP-RPC-T200 CFRP-RPC-T300 Present study CFRP-RPC-T25-L15d 25 180 Slip 284.4 Slip CFRP-RPC-T100-L15d 100 324.8 CFRP-RPC-T200-L15d 200 386.5 CFRP-RPC-T300-L15d 300 462.0 Ref.[17] AT30 30 160 Fracture 126.3 Fracture AT100 100 Fracture 151.1 Fracture AT200 200 Slip 221.0 Slip Notes: Failure modes of tensile failure in CFRP bar and slip failure in CFRP-RPC interface were abbreviated as fracture and slip, respectively. -
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