腐蝕預力混凝土基樁安全評估與補強之研究

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题名:	腐蝕預力混凝土基樁安全評估與補強之研究
作者:	林澄政;Cheng-Zhen Li
贡献者:	土木工程研究所
关键词:	鋼筋混凝土;腐蝕;棧橋;基樁;纖維強化塑膠;補強;延展性;corrosion;prestressed concrete;FRP;retrofit;pile;ductility
日期:	2001-07-12
上传时间:	2009-09-18 17:05:38 (UTC+8)
出版者:	國立中央大學圖書館
摘要:	碼頭棧橋基樁因位於乾溼交替之潮汐區，浪潮的拍打與高氯離子濃度之環境將加速混凝土基樁鋼筋之腐蝕。為了提升碼頭棧橋之服務性與耐震能力，減少結構損壞所造成之社會成本付出，補強與防蝕是兩項解決該問題的根本之道。不同於一般的橋柱補強，腐蝕發生的位置不一定會發生在結構物之最大彎矩處，但腐蝕位置必然會成為該構件的脆弱面，成為結構物之整體力學行為之關鍵。本論文依據碼頭現場基樁常見之腐蝕損傷模態，製作四種損傷型式的基樁試體，進行補強前後之結構行為測試。四種預先製作的損傷類型分別為：(1)無損傷樁；(2)混凝土部份剝落，箍筋鏽蝕一半；(3) 混凝土部份剝落，箍筋完全鏽蝕；(4) 混凝土部份剝落，箍筋全部鏽蝕，預力主筋部份鏽斷。四種類型基樁未經修補前在實驗室分別進行試驗，以便了解鋼筋腐蝕對於基樁承載力的影響；之後將基樁損傷部份以強化纖維套筒外纏繞FRP方式進行補強，補強後的基樁也進行試驗以便觀察承載能力回復狀況。此外，基於過去對於RC橋柱補強理論，本論文構建了腐蝕中空預力基樁圍束補強的分析架構。對於修補前與修補後基樁，分別經由側向力-位移曲線、基樁破壞形式與韌性來進行比較，對基樁補強方式提出建議。考慮鋼筋與混凝土材料非線性及圍束效應所撰寫之電腦分析程式可預估四類損傷基樁斷面在修補前後之非線性彎矩與曲率關係，以及基樁受力後之應變分布來預測其破壞發生位置，並估算其側向力與位移之關係；同時也對於損傷斷面經過補強後，彎矩與曲率的回復，以及新的應變分布關係來檢核此腐蝕基樁修補方式的成效。研究結果顯示，經過本論文所提出之方法分析後並使用強化纖維套筒外纏FRP之修補工法，可有效提供腐蝕預力基樁的強度與韌性之回復。 Marine piling has been a common problem for structural engineers in that the wetting and drying due to storm activity and tidal fluctuations result in accelerated deterioration of concrete pilings. Although the corroded site is not necessarily the section under the largest bending moment, but it is sure to be a weak and critical section of the pile. In order to extend the service life of the structures, the strengthening and corrosion protection are two possible solution procedures. Although the FRP tow-sheet patching method has been showing its capability in strengthening non-corroded RC structures, the effectiveness may be affected by the corrosion of rebars. In this thesis, cylindrical hollow prestressed reinforced concrete piles repaired by fiber reinforced plastic (FRP) along with newly developed cathodic protection casing are tested in the laboratory under static and cyclic loadings. Those test piles are characterized in four different groups according to the states of corrosion damage: (I) no corrosion damage; (II) 50% corrosion damage of spiral reinforcements; (III) spiral reinforcements are completely corroded; and (IV) spiral reinforcements completely corroded and prestressed rods partially corroded. Corrosion damage conditions are simulated by reducing the effective cross sectional area of the steel reinforcements inside piles. Then the load carrying capacity of all the piles with or without FRP strengthening/corrosion protection casing are tested in the laboratory. Through the experimental results, the axial load-moment response curves, failure modes and ductility of the piles are evaluated. It is shown that the retrofit technology applied to the tested pile can effectively recover the load carrying capacity of piles of various damage conditions. An analysis procedure for the retrofit of prestressed pile is developed based on the seismic retrofitting theories of RC column to predict the ultimate load carrying capacity of each corrosion damaged pile before and after retrofit. The accuracy and effectiveness of this analysis procedure were verified by comparing the predictions with the experimental results. It is planed that this analysis and evaluation procedure can be a reference for structural engineers to evaluate the loading capacity of corroded marine piles.
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