Experimental Research on Stress Relaxation Properties of CFRP Rods
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摘要: 为合理确定湖北十淅高速丹江口水库特大桥地锚桥台预应力碳纤维增强复合材料(Carbon Fiber Reinforced Polymer,CFRP)筋材的松弛损失,对不同应力比下所用CFRP筋材的应力松弛效应进行了试验研究。基于黏结式锚具和机械压接式锚具锚固的CFRP筋材试件的轴向拉伸试验结果,明确了不同锚固形式对CFRP筋材破坏形态的影响及CFRP筋材的材料性能;基于CFRP筋材试件1 000 h的应力松弛试验,获得了不同应力水平下CFRP筋材应力松弛的发展规律。结果表明:黏结式锚具锚固的轴拉试件发生了理想的筋材拉断爆裂破坏,但应力松弛试件在试验过程中应变变化较大;机械压接式锚具锚固的轴拉试件提前发生了CFRP筋材的层裂剥离破坏,但应力松弛试件在试验过程中应变变化较小,满足GB/T 21839—2019中应力松弛试验的相关要求。随着初始应力比的提高,CFRP筋材的应力松弛越大,初始应力比分别为0.53、0.63和0.82的试件1 000 h的松弛率分别为1.06%、1.65%和2.31%;CFRP筋材应力松弛的发展收敛较快且随初始应力的增加而更快趋于稳定,初始应力比为0.53、0.63和0.82的试件24 h的应力松弛量分别为1 000 h的45.3%、58.8%和59.7%,200 h的应力松弛量分别为1 000 h的78.3%、81.2% 和 82.7%;基于试验结果,建立了CFRP筋材应力松弛的预测模型,且具有较高预测精度,并预测了丹江口水库特大桥地锚桥台所用预应力CFRP筋材10年,30年、50年和100年的松弛率分别为1.91%、2.18%、2.32%和2.52%。
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关键词:
- 应力松弛 /
- 碳纤维复合材料(CFRP)筋材 /
- 锚固形式 /
- 初始应力比 /
- 预测模型
Abstract: In order to determine the relaxation loss of prestressed carbon fiber reinforced polymer (CFRP) rods in the ground anchor abutment of Danjiangkou Reservoir Bridge of Shixi Expressway in Hubei Province, the stress relaxation of CFRP rods under different stress ratios was experimentally studied. Based on the axial tensile test of CFRP rod specimens anchored by bonded anchorage and mechanical crimping anchorage, the influence of different anchorage forms on the failure mode of CFRP rods and the material properties of CFRP rods were clarified; based on the 1 000 h stress relaxation test of CFRP rod specimens, the development laws of stress relaxation of CFRP rods at different stress levels were obtained. The results showed that the specimens anchored by bonded anchorage had an ideal bursting tensile failure under axial tension, but the strain of the specimens changed greatly during the stress relaxation test; the specimens anchored by mechanical crimping anchorage failed prematurely with the mode of the spallation and peeling of the CFRP rods under axial tensile, but the strain of the specimens changed little during the stress relaxation test, which could meet the relevant requirements of the stress relaxation test in GB/T 21839—2019. The stress relaxation of the CFRP rods increased with the increase of the initial stress ratio. The relaxation rates of specimens with initial stress ratios of 0.53, 0.63 and 0.82 were 1.06%, 1.65% and 2.31% after 1 000 h, respectively; the development of stress relaxation of CFRP rods converged rapidly and tended to be more stable with the increase of initial stress. The stress relaxation of specimens with initial stress ratios of 0.53, 0.63 and 0.82 at 24 h were 45.3%, 58.8% and 59.7% of that at 1 000 h, respectively. The stress relaxation of specimens with initial stress ratios of 0.53, 0.63 and 0.82 at 200 h were 78.3%, 81.2% and 82.7% of that at 1 000 h, respectively; based on the test results, the prediction model of stress relaxation in CFRP rods was established with high prediction accuracy, and the relaxation rates of prestressed CFRP rods in ground anchor abutment of Danjiangkou Reservoir Bridge in 10, 30, 50 and 100 years were 1.91%, 2.18%, 2.32% and 2.52%, respectively. -
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