【正文】 繞度因混凝土的收縮應(yīng)變可以忽略不計(jì)。m。Hall 、 Ghali 和 Masia et al詳細(xì)地描述了該方法論。50%的滑移發(fā)生在加載后的3個(gè)星期內(nèi)。在當(dāng)前的測(cè)試中沒(méi)有記錄相對(duì)濕度。Plevris和Triantafillou2在用玻璃鋼條加固的鋼筋混凝土梁和較對(duì)參照標(biāo)本（無(wú)玻璃鋼）梁上觀(guān)察到類(lèi)似的外部響應(yīng)。雖然沒(méi)有測(cè)試，但額外增加的碳纖維貼片有望增加梁極限抗彎承載力。這樣的裂縫很難看到，除非有值得注意的寬度，是因?yàn)橛袕埦o的碳纖維貼片。荷載的轉(zhuǎn)移是用液壓千斤頂逐漸降低混凝土塊到梁上。對(duì)于梁二，電子彈簧儀表被安置在靠近每個(gè)具體的碳纖維帶的梁端。兩根混凝土梁是同時(shí)澆筑的，且在碳纖維貼片和玻璃纖維增強(qiáng)塑料帶運(yùn)用前10個(gè)月，它們是平放于地面的（完全支撐）。然而，蠕變變形比單從混凝土徐變預(yù)測(cè)的更大，表面這都緣于環(huán)氧樹(shù)脂的蠕變變形。因?yàn)樵谝旬a(chǎn)生的應(yīng)力水平下還沒(méi)有觀(guān)察到碳纖維復(fù)合材料的蠕變，可額外蠕變可能已經(jīng)在玻璃鋼條和混凝土梁界面之間產(chǎn)生。在所有上述的模型，不管怎樣，發(fā)生在玻璃鋼條與梁受拉面之間粘結(jié)層的蠕變的影響被忽視了。玻璃鋼條通常直接用環(huán)氧膠粘劑粘結(jié)于精制的混凝土表面。本實(shí)驗(yàn)的目的是評(píng)估環(huán)氧膠粘劑的蠕變的重要性，以及這樣的蠕變是否允許玻璃鋼條隨著時(shí)間的推移有卸載荷載的作用。 MPa (4900 177。 epoxy adhesive。 and (b) Beam 2, considering bined effect of creep of concrete and creep of epoxy adhesive.論文翻譯普通鋼筋混凝土梁和纖維增強(qiáng)聚合物加固的鋼筋混凝土梁的徐變效應(yīng)監(jiān)測(cè)了兩根具有相同尺寸和材料性能的RC梁的長(zhǎng)期繞度行為。兩種分析方法表明：粘結(jié)層蠕變能解釋預(yù)測(cè)和實(shí)際行為之間差異的現(xiàn)象。對(duì)（用玻璃鋼條加固于混凝土梁外表面的）梁的隨時(shí)間發(fā)生的行為（蠕變和收縮）的研究還很少。Hall and Ghali的提議把實(shí)測(cè)繞度和用ACI and CEBFIP的方法預(yù)測(cè)的繞度進(jìn)行比較。它被認(rèn)為能消除玻璃鋼條的壓力，在持續(xù)荷載作用下，一個(gè)適用性的觀(guān)點(diǎn)認(rèn)為它能使玻璃鋼條效應(yīng)減弱。）加強(qiáng)。碳纖維貼片在順纖維方向的彈性模量為165Gpa，抗拉強(qiáng)度為2800Mpa（生產(chǎn)廠(chǎng)家提供的數(shù)據(jù)）。對(duì)于梁一，預(yù)計(jì)荷載將使梁受拉區(qū)混凝土開(kāi)裂，但是受壓區(qū)混凝土的應(yīng)力和受拉區(qū)鋼筋的應(yīng)力還處在彈性階段。實(shí)驗(yàn)結(jié)果與討論一經(jīng)加載。因此，彎矩值恒定區(qū)段的混凝土必須先有很多的小裂縫以使FRP條的應(yīng)力保持不變。長(zhǎng)期繞度是由于混凝土徐變是直接繞度的一個(gè)函數(shù)，它與梁截面的剛度和裂縫情形有關(guān)。相似的趨勢(shì)在梁跟梁上都有發(fā)生。從加載起，碳纖維貼片一個(gè)末端的運(yùn)動(dòng)就基本穩(wěn)定，只有很小一部分運(yùn)動(dòng)是逐步發(fā)生于另一末端的。所以時(shí)程分析和有限元模型得到發(fā)展，并用他們檢驗(yàn)混凝土徐變和環(huán)氧基樹(shù)脂蠕變對(duì)長(zhǎng)期繞度的影響。后面計(jì)算兩根梁跨中長(zhǎng)期繞度要用最終開(kāi)裂彎矩。對(duì)控制梁一而言，調(diào)整混凝土最終徐變系數(shù)，提供一個(gè)最小二乘方以最佳匹配它的繞度預(yù)測(cè)值和實(shí)驗(yàn)測(cè)試值。m）。這些開(kāi)裂彎矩最佳擬合了代表梁繞度（跨中直接繞度測(cè)量相對(duì)于自重繞度）的測(cè)試值，而不是源于混凝土的開(kāi)裂強(qiáng)度。首先，運(yùn)用CEBFIP 和ACI的簡(jiǎn)單程序。從觀(guān)察到的徐變變化率變化，我們相信徐變變化率具有季節(jié)性，并隨相對(duì)濕度而變化。繞度曾長(zhǎng)率隨時(shí)間是變化的。粘結(jié)于梁二的碳纖維貼片的末端的相對(duì)滑移量與時(shí)間相對(duì)應(yīng)的圖如圖3所示。FRP條必須保持平衡，因此，F(xiàn)RP條大規(guī)?？焖俚暮痛蟮淖兓遣豢赡艿?。在加載后的第一個(gè)24小時(shí)內(nèi)要多次記錄數(shù)據(jù)，然后在第一個(gè)月內(nèi)要每天記錄一次數(shù)據(jù)，最后逐漸是每3天、每周、每?jī)芍艿礁L(zhǎng)的時(shí)間段記錄一次數(shù)據(jù)。使之產(chǎn)生4個(gè)點(diǎn)的彎曲。在梁二的每個(gè)剪跨處，碳纖維貼片以U型形式包裹著梁的兩側(cè)和受拉面。實(shí)驗(yàn)項(xiàng)目測(cè)試樣品和材料兩跟相似的鋼筋混凝土梁是由同一批混凝土澆筑而成（圖一）。在此，我們使用兩種不同的方法來(lái)確定環(huán)氧基樹(shù)脂的蠕變是否能解釋所觀(guān)察到的梁的不同現(xiàn)象：一步一步的時(shí)間分析，允許混凝土和環(huán)氧基樹(shù)脂在每個(gè)時(shí)間步內(nèi)的蠕變?cè)隽窟_(dá)到平衡，有限元（FE）與剪切流模型允許在環(huán)氧膠粘劑層。在這方面，實(shí)驗(yàn)研究結(jié)果以及瞬時(shí)的和伴隨時(shí)間發(fā)生的梁繞度分析預(yù)測(cè)都被描述了。同樣，正如最近一些研究者推薦的那樣，如果給玻璃鋼條施加預(yù)應(yīng)力，蠕變可以減弱原始的內(nèi)力。玻璃鋼條加固梁的蠕變變形并不像從控制標(biāo)本梁所預(yù)測(cè)的那樣。 therefore, rapid and large variations in force in the strip are not possible, as there is no mechanism to acmodate such stress variation. Hence, the concrete in the constantmoment section has to crack with a large number of very thin cracks so that the strain in the FRP remains constant. Several months after loading, a thin flexural crack could be seen extending from the tension face of Beam 2 close to the beam midspan. The CFRP strips significantly increased the cracking moment capacity of Beam 2. Although not tested, the additional FRP reinforcement was also expected to increase the ultimate moment capacity of the beam.The longterm midspan deflections (total deflection minus the initial deflection) of both beams are shown in Fig. 2, plotted versus time after loading up to 2470 days of loading. The relative slip movements versus time at each end of one of the CFRP strips bonded to Beam 2 are shown in Fig. 3. Several observations can be made:1. The longterm deflection of Beam 2 is significantly less than that of Beam 1. Longterm deflection due to concrete creep is a function of the immediate deflection, which depends on crosssectional stiffness and cracking status. Beam 1 cracked much sooner than Beam 2.2. The longterm deflection of Beam 2 constitutes a larger proportion of its immediate deflection pared with Beam 1. Plevris and Triantafillou2 observed a similar response in beams externally reinforced with FRP strips pared to their control specimen (no FRP).3. The midspan deflection for Beam 2 does not appear to be “catching” that of Beam 1. That is, at first appearance, there is no indication that the CFRP reinforcement is unloading, thereby being ineffective against the sustained load.4. The rate of increase of deflection changes with time. This is particularly evident when pared to the smooth curves of predicted longterm deflections discussed and presented in the following sections (Fig. 2, 4, and 5). Similar trends occur for both beams. The periods of reduced rate of increase of deflection coincide with the summer months and those of increased creep coincide with the winter months. In the calculation of creep coefficient using CEBFIP,10 the creep coefficient reduces as the relative humidity increases, implying a reduced rate of creep during periods of higher relative humidity. The relative humidity was not recordedduring the current tests. However, relative humidity was recorded during creep tests by Hall and Ghali,6 conducted in the same laboratory as these tests. Their results showed relative humidity varying between 5 and 50%, with a summertime average of approximately 35% and a wintertime average of approximately 10%. The observed changes in creep rate are thus believed to be seasonal and depend on changes in relative humidity.Fig. 2—Experimentally measured longterm midspan deflection versus time af