【正文】 CORROSION AND PRESTRESSED CONCRETE BRIDGES Adrian T. Ciolko, 腐蝕和預應力混凝土橋梁 阿德里安 Abstract The impact on bridge reliability, of prestressing steel deterioration and tendon rupture created by corrosion mechanisms, is much more critical and rapid than that of any other ponent of a prestressed concrete bridge. Additionally, deterioration of embedded prestressing reinforcement in these structures may not necessarily be made visible through manifestation of external distress in the Concrete. 摘要 腐蝕機制 引起 預應力 鋼筋的 惡化和 斷裂，進而對 橋梁 的 可靠性 產(chǎn)生 影響 ，這比對 預應力混凝土橋 的 其他 部分的影響更加嚴重，也更加迅速。 此外， 在這些結(jié)構(gòu)中 ，有粘結(jié) 預應力鋼筋的惡化 也 不 必要 通過 混凝土外部糟糕的 狀況 表現(xiàn)出來。 Initiating mechanisms and particular forms of corrosion affecting prestressed concrete structures are described based on the author’s experience. These degradation mechanisms include: ? Chlorides and Corrosion ? Concrete Carbonation Effects ? Influence of Concrete Cracking ? Electrochemical (Macrocell) and Pitting Corrosion ? Stress Corrosion Cracking and Steel Embrittlement ? Fretting Corrosion ? Corrosion and Fatigue 關(guān)于 腐蝕 影響 預應力混凝土結(jié)構(gòu) 的最初 機制和特定形式 的 描述 是 基于作者的經(jīng)驗。這些退化機制包括： ? 氯化物和腐蝕 ? 混凝土碳化影響 ? 混凝土裂縫的影響 ? 電化學 (小區(qū) ) 和孔蝕 ? 應力腐蝕開裂和 鋼的脆斷 ? 微動腐蝕 ? 腐蝕和疲勞 Recently, prestressed, posttensioned concrete structures have been thought to be threatened by certain premature performance impairments worldwide, predominately when defects were present. These problems may continue to manifest themselves. Therefore, corrosion preventative methods and need for scrutiny during construction and maintenance needs will be described. For existing structures experiencing evidence of premature distress, the author discusses casestudy based investigative techniques and available rehabilitation Strategies. 最近， 世界各地的 預應力、 后張法預應力 混凝土 結(jié)構(gòu) 已經(jīng)被認 為受到某些 早期 性能破壞 的威脅， 尤其是 已經(jīng) 存在的缺陷。這些問題可能繼續(xù) 危害結(jié)構(gòu) 。因此， 我將對 預防 腐蝕 的 方法和 施工 與 維護 期間 的 檢測 進行介紹。 對于遭受 早期破壞 的 現(xiàn)有 結(jié)構(gòu)， 作者討論案例研究 是 基于 探測 技術(shù)和 有效的修 復 手段 。 1 Vice President, Construction Technology Laboratories, Inc., 5400 Old Orchard Road, Skokie, IL 60077. 1 Copyright ASCE 2020 Structures 2020 Structures Congress 2020 Introduction The first prestressed concrete bridge in the US was constructed in 1950。 the pace of acceptance for this construction technology accelerated rapidly。 most all concrete bridge superstructures in existence today were built in that fashion. Assuring success in new construction and extending service life of prestressed and post tensioned concrete bridges requires attentiveness to the distinctive characteristics and behaviors inherent to this particular construction technology. 介紹 美國的第一個預應力混凝土橋建于 1950 年 ； 接受這種施工技術(shù) 的步伐迅速 加快 。在這個時尚潮流中建造了當今大多數(shù)的 混凝土橋梁上部結(jié)構(gòu)。 確保 成功 應用于新型結(jié)構(gòu) 和延長預應力和后張 法 預應力混凝土橋梁 的使用壽命 需要 專注于這種 特殊施工技術(shù) 的 顯著特點 和 固有特征 。 This paper discusses considerations necessary for achieving the potential low maintenance service life these bridges can offer. These observations are derived from the author’s experience in investigating and evaluating prestressed, posttensioned concrete bridges, and developing investigative and rehabilitation solutions at the CTL Structural Engineering Laboratory since 1988. While the durability of prestressed concrete can be influenced by behaviors of both the concrete and reinforcement, recent construction trends and post tensioned concrete bridge performance observations have focused more attention on preserving the condition of prestressing steel. Consequences of prestressing steel deterioration are most serious. Awareness of these features is a key element to construction of long lasting prestressed bridges and extending life of older, serviceable structures. 本文討論了實現(xiàn)這些橋梁潛在的低維護 使用 壽命 所需的考慮。 自 1988 年以來 ， 作者 在 CTL 結(jié)構(gòu)工程實驗室 調(diào)查和 評估 預應力 、 后張法預應力混凝土橋梁、開發(fā)檢測 和 加固 解決方案 ， 這些 觀測結(jié)論 就源于 這期間 的 經(jīng)驗 。 混凝土和鋼筋 兩者的性能都 影響預應力混凝土的耐久性 ， 但是當 近 的 建設(shè)趨勢和后張預應力混凝土橋梁性能 檢測 都 更多 地 集中 于 預應力 鋼筋 的 維護 。預應力 鋼筋 惡化的后果是最嚴重的。對這些 特點 的認識 是對建設(shè)持久的預應力 橋梁和延長 舊 的 可用結(jié)構(gòu) 壽命 的 一個關(guān)鍵 因 素。 Function of Prestressing Reinforcement in Bridge Design and Construction Most concrete highway bridges are prised of prestressed concrete in two predominant fabrication/construction categories。 namely pretensioned and post tensioned, with more than 90% representing pretensioned. The geometric cross sections and design/construction procedures used represent a broad range of possible structural design configurations, both precast and castinplace。 the interested reader is encouraged to obtain information from organizations such as the Prestressed/Precast Concrete Institute, the Post Tensioning Institute and the American Segmental Bridge Institute for indepth design and construction guidance for this technology, since exploring its plexity is beyond the scope of this paper. 預應力加固橋梁 設(shè)計和施工中的作用 最具體的公路橋梁是由組成的預應力混凝土在兩個主要制造 /建筑類別 ；即先張法和后張法，有 90%以上表示先張法預應力。幾何截面和使用的設(shè)計 /施工程序代表的范圍廣泛的可能結(jié)構(gòu)設(shè)計配置、 預制和強制轉(zhuǎn)換的地方 ；有興趣的讀者應該鼓勵從預應力 /預制混凝土研究所、 后張法研究所和美國節(jié)段橋梁研究所深入設(shè)計和施工指導對這一技術(shù)，等組織獲得的信息，因為探索它的復雜性是超出了本文的范圍。 Prestressed (less monly known as pretensioned) concrete is made by stressing the reinforcement between fixed bulkheads and casting concrete around the steel elements. Following concrete curing, the steel strand is released at the bulkhead, transferring pressive stress and added stiffness into the concrete. Most all pretensioned concrete bridge ponents are precast in specialized fabrication yards, then shipped and erected onsite. Posttensioned concrete for bridges predominately contains multiple strand or bar tendons. Tendons are stressed against builtin multipoint anchorages。 and tendon forces are internally resisted by the concrete mass in pression. Tendons are installed in sheathing or ducts preplaced in the formwork prior to casting. Tensile forces in stressed tendons are transferred to concrete through specialized anchorage hardware, creating pression in the concrete, ma