鋼筋混凝土構造新型碳纖維補強技術之試驗與分析

Experiments and analysis on the novel technique for RC members retrofitted by carbon fiber reinforced polymers

吳穎涵(Ying-Han Wu)

指導教授 ： 林至聰

國立臺北科技大學/工程學院/工程科技研究所/博士(2013年)

https://doi.org/10.6841/NTUT.2013.00138

摘要

碳纖維補強鋼筋混凝土構造的實施大多以碳纖維貼片與膠結樹脂以手積層或預浸布積層成形，由於補強系統為透過膠結樹脂傳遞應力方可發揮束制補強桿件變形、提供補強勁度之效果，膠結界面之強度為影響補強性能之主要因素，若膠結面之混凝土發生裂縫，可能導致膠結界面之破壞影響碳纖維強度發揮；再者，鋼筋混凝土構造多為矩形，角隅效應往往造成碳纖維提早斷裂以及碳纖維單向度之纖維特性使水平構造之平面無法提供與纖維方向垂直之強度；以上列舉碳纖維補強之缺失顯見現今碳纖維補強技術仍有一定程度的進步空間。
針對上述議題，本研究提出碳纖維補強搭配碳纖維錨栓之新型補強技術，設計碳纖維錨栓提供碳纖維與混凝土間之界面強度，同時改善構造之角隅效應，更可在矩形鋼筋混凝土柱補強上可設計提供柱面圍束；本研究提出碳纖維錨栓設計理論與錨定行為理論，以及碳纖維錨栓應用於各種型式補強之設計理論與分析理論。此些設計與分析理論皆規劃進行補強試驗，包含探討碳纖維錨栓錨定行為拉拔試驗、碳纖維錨栓圍束補強之矩形柱單向度軸壓試驗以及矩形鋼筋混凝土柱耐震補強試驗，驗證本研究碳纖維補強技術之實用性與理論之合理性。
特定之鋼筋混凝土構造對抵抗疲勞載重之能力存在較高之需求性，鋼筋混凝土疲勞破壞之通識為微觀區域形成局部微裂縫，在疲勞應力之循環作用下微裂縫擴張與應力集中，最終造成突發性之破壞，即便荷重低於構造設計容許強度，在疲勞載重做用下，破壞仍有可能發生；對老舊之鋼筋混凝土構造進行補強已為普遍之認知與必行工作，而對於經由碳纖維補強後之鋼筋混凝土構造以及碳纖維補強系統疲勞特性之試驗與分析相對較為欠乏，因此，本論文以特定頻率之載重探討碳纖維補強鋼筋混凝土梁受重複疲勞載重之行為，測試碳纖維補強鋼筋混凝土梁之疲勞特性並分析其反應以建立碳纖維補強系統之安全指標。

關鍵字

鋼筋混凝土 ； 結構補強 ； 碳纖維 ； 錨栓 ； 圍束混凝土 ； 疲勞

並列摘要

In this paper, two subjects were studied. For the first one, the novel retrofit technique-CFRP Anchor was presented to improve the retrofit performances for RC structures. The testing bond performance and design theorems were discussed and tested in practical experiments with a total of forty six specimens. Test programs for the fiber bolt and spread tails, the components of CFRP anchors, were carried out under tensile loading. To access the applicability for the technique, the rectangular RC column retrofitted by using CFRP combined with CFRP anchors was presented to improve the seismic performances. Seven full-scale RC columns in two series were constructed with low transverse reinforcement ratios and tested under lateral cyclic loadings with a constant axial load. Experimental results showed that the benchmark specimen, which was not retrofitted, was shear failure. The proposed technique avoids the occurrence of the premature CFRP breakage on corner zones and provides confinement on column faces as the comparison to tests using CFRP alone. The use of CFRP anchors significantly improved the behavior of CFRP wrapping on rectangular columns, such as increased the ductility and the energy dissipation. In addition, a flexural strengthening system of longitudinal CFRP bonded with CFRP anchors doweling into column footings was tested and verified.
Moreover, a total of eleven rectangular RC columns with low transverse reinforcement ratio were constructed to test the confining performance using different retrofit schemes including the proposed CFRP combined with CFRP anchor technique. Among them, one was tested as benchmark; one was purposely constructed with larger transverse reinforcement ratio; five were retrofitted by using CFRP wrapping combined with CFRP anchors; and the other four were retrofitted by using different shapes of steel jacketing alone or with adhesive anchors. All the specimens were subjected to monotonic incremental axial force until failure occurred. Experimental results demonstrated that the compression ductility of the specimens retrofitted by CFRP anchors was significantly improved compared with those retrofitted by using only CFRP wrapping alone. On the other hand, the specimen with octagonal steel jacketing performed better than all other specimens not only on ductility but also on strength. An model considering the contribution of the retrofit material was proposed and validated in the numerical analysis.
The second subject in this paper is the effects of fatigue leading to crack formation and potential durability-bonding problems in reinforced concrete (RC) beams strengthened by CFRP. These effects are shown to cause CFRP debonding and loss of load carrying capabilities under static or low cyclic loading. Two series of RC beams with CFRP strengthening system are constructed and designed to fail in shear and flexural failures, respectively, under static loading. Repeated loading tests are conducted according to various loading ranges and loading cycles, and the experimentally determined fatigue properties are discussed. The test result show that it is possible to eliminate the debonding modes for longitudinally bonded CFRP using U-wrap CFRP combination. The fatigue loads tested a significant effect on concrete rather than the CFRP system especially for the strengthened beams bearing a higher shear level. Moreover, the equation to fit the testing S–N curve and the discussion of the stress in the component materials could be used for fatigue life predictions of beams with CFRP strengthening systems.

並列關鍵字

RC ； Retrofit ； CFRP ； Anchor ； Confined concrete ； Fatigue

參考文獻

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