【正文】 ve strength of the concrete, as determined from 100 mm (4 in.) diameter, 200 mm (8 in.) high cylinders—cast from the same batch of concrete as the test beams—was 177。兩根梁均持續(xù)負(fù)荷超過(guò)61/2年。一種普及的應(yīng)用，廣泛使用于實(shí)踐之中，那就是在普通鋼筋混凝土受拉面粘結(jié)玻璃鋼條以增加梁的抗彎能力。類似的方法被用于混凝土箱梁在抗壓凸緣的復(fù)合玻璃碳纖維增強(qiáng)聚合物(GFRP)與和粘結(jié)于張拉面的碳纖維增強(qiáng)聚合物(CFRP)。當(dāng)僅考慮混凝土蠕變時(shí)，從測(cè)量簡(jiǎn)單梁的蠕變變形，不能預(yù)測(cè)有玻璃鋼條加固的梁的蠕變變形。實(shí)驗(yàn)和分析工作的執(zhí)行顯示：情況更加復(fù)雜。 MPa，該值是從直徑為100mm，高 200mm的圓柱測(cè)量而得，而這批圓柱是用澆筑梁的同一批混凝土澆筑而成。梁由于自重，在跨中產(chǎn)生繞度，該繞度可以用安裝在輕跨度為3200mm鋼架上的千分表測(cè)量。荷載是通過(guò)懸掛混凝土塊于每根梁上表面。第一次加載的時(shí)候，在梁二上沒(méi)有觀察到彎曲裂紋。碳纖維貼片顯著提高了梁二抗裂彎矩。與梁一相比，梁二的長(zhǎng)期撓度構(gòu)成其直接繞度的比例比梁一大。在徐變系數(shù)計(jì)算中用CEBFIP，當(dāng)相對(duì)濕度增加，徐變系數(shù)降低，意味在相對(duì)濕度大的時(shí)間段徐變?cè)鲩L(zhǎng)率降低。在2470天內(nèi)，貼片整個(gè)長(zhǎng)度范圍內(nèi)的平均滑移量接近60微應(yīng)變，這意味著貼片的應(yīng)力平均損失9Mpa，相當(dāng)于每條帶損失1KN的力。兩種方法的目的都是為了評(píng)估梁的長(zhǎng)期繞度受影響于混凝土的徐變和收縮。用源于梁一的最終徐變系數(shù)去分析梁二是一個(gè)有根據(jù)的設(shè)想，因?yàn)閮筛菏怯猛慌炷镣瑫r(shí)澆鑄而成，且在相同環(huán)境下進(jìn)行加載實(shí)驗(yàn)。澆鑄后，兩根梁負(fù)荷了近300天，總收縮應(yīng)變的90%已經(jīng)完成。開(kāi)裂彎矩值的巨大差異凸顯了碳纖維貼片的加固效果。用CEBFIP 和 ACI分析繞度預(yù)言的結(jié)果第一次用CEBFIP方法來(lái)預(yù)測(cè)兩跟梁的跨中的直接繞度。這份觀察報(bào)告與Choi et ，也證實(shí)了環(huán)氧基樹(shù)脂大部分蠕變發(fā)生在相對(duì)比較早的時(shí)期內(nèi)。然而，在同一實(shí)驗(yàn)室的同一階段，Hall 和Ghali在裂縫試驗(yàn)中記下了相對(duì)濕度。對(duì)于梁二的跨中繞度并不像梁一那樣被“清楚理解”。兩根梁的跨中長(zhǎng)期繞度（總繞度減去初始繞度）如圖2所示。這是因?yàn)樵诮孛鎻澗夭蛔兊膮^(qū)域FRP條的張拉應(yīng)變保持不變。然后拿走液壓千斤頂。小心地把彈簧儀表的偏移尖端定位于碳纖維貼片暴露的末端。梁一被設(shè)計(jì)為參照樣本，采用環(huán)氧粘合劑把兩根碳纖維復(fù)合材料條粘于梁二的受拉面表面。已報(bào)道的實(shí)驗(yàn)方案的目的是確認(rèn)環(huán)氧樹(shù)脂蠕變的存在，而不是復(fù)制一個(gè)實(shí)用的改造方案。蠕變機(jī)理被期待為環(huán)氧基樹(shù)脂的一種簡(jiǎn)單的流體剪切應(yīng)力，即發(fā)展到在玻璃鋼條和混凝土之間產(chǎn)生應(yīng)力的程度。也就是說(shuō)，假定梁的受拉面和玻璃鋼條之間是理想的約束和協(xié)調(diào)的應(yīng)變。這些玻璃鋼條可能被機(jī)械的錨固于RC梁梁端附近或者被附加抗剪鋼筋支撐于梁端附近，通常采用U字型的玻璃鋼條。在玻璃鋼條的兩端的滑移也被監(jiān)測(cè)了。 328 psi).Fig. 1—Test specimens, test setup, and strain distribution.The two beams were cast together and stored—fully supported—for 10 months before the CFRP strips and GFRP wraps were applied. One beam (Beam 1) was designated as a control deflection。 = ) and Beam 2 (reinforced with steel and FRP), including effects of concrete creep, tension stiffening of concrete (), and stress relaxation of FRPepoxy posite (anddays).Results of analytical deflection predictions using CEBFIP10 and ACI11The CEBFIP10 approach was first used to predict the immediate midspan deflections of both beams. The model predictions were calibrated against the experimental results by adjusting the cracking moment for each beam. These cracking moments are bestfit values representing the observed deflections (immediate midspan deflection measured relative to the selfweight deflection) in the beams and not derived from the cracking strength of concrete. The cracking moments were determined in this way because the tensile strength and design shrinkage strain of the concrete, required for direct estimation of the cracking moments, were not measured in the experimental program. The cracking moments determined were used later in calculating the longterm midspan deflections for the two beams. The cracking moment capacities obtained from the calibration were ( .) and ( .), respectively, for Beams 1 and 2. The large difference highlights the strengthening effects of the CFRP strips. The difference is also consistent with the observation of minor cracking for Beam 2, whereas significant cracking was observed in Beam 1 (note that the maximum bending moment due to beam selfweight and applied sustained loading is [ .]).The longterm midspan deflections of each of the beams were then predicted for all times after loading, at which experimental readings were recorded. The ultimate creep coefficients for concrete were adjusted to provide a leastsquares best fit between the predicted and experimental deflection values for the Control Beam 1. The same ultimate creep coefficients were then used to predict the longterm deflections for Beam 2, assuming no creep in the adhesive bonding of the CFRP to the concrete. The use of the ultimate creep coefficients derived from Beam 1 to analyze Beam 2 is a valid assumption, as both beams were cast from the same concrete batch at the same time and loaded at the same environment. Deflections due to shrinkage strains in the concrete were neglected. The two beams were loaded approximately 300 days after casting, after which timeapproximately 90% of the total shrinkage strain was Further, as the second beam was not “strengthened” until 285 days, the drying creep of the two beams was assumed to be the same. Fig. 5—Longterm deflections at midspan of beams using FE method: (a) Beam 1, considering creep of concrete。使用了兩種分析方法：一種是時(shí)程分析，另一種是有限元（FE）模型。因此，雖然玻璃鋼條仍然可以協(xié)助承受額外的活荷載，增加的持續(xù)荷載可能超過(guò)使之成為原加固梁的能力。為了觀察鋼筋混凝土梁隨時(shí)間而發(fā)生的繞度，它的制作過(guò)程和實(shí)驗(yàn)步驟都被呈現(xiàn)出來(lái)了。研究意義蠕變對(duì)用玻璃鋼條加強(qiáng)于梁外表面的RC梁的潛在影響被考慮到了。每根梁長(zhǎng)3500mm，梁寬280mm，梁高180mm，從箱梁頂部至底部135mm位置處有4根縱向鋼筋（，單根面積100mm178。碳纖維貼片纖維方向的單向性與梁長(zhǎng)方向?qū)R。這種荷載水平的目的是要使兩根梁達(dá)到工作的范圍。加荷載的梁位于裝有空調(diào)的實(shí)驗(yàn)室地下室，在這里平均溫度相對(duì)于時(shí)間是保持不變的。因?yàn)闆](méi)有任何原理適應(yīng)這種壓力的變化。可得出如干觀察結(jié)果：梁二的長(zhǎng)期撓度明顯減少梁比一的。當(dāng)與下面所討論和呈現(xiàn)的較平穩(wěn)的長(zhǎng)期繞度曲線（圖5）相比，這一點(diǎn)尤其明顯。加載后不久，發(fā)生于混凝土和碳纖維貼片末端的相對(duì)滑移如圖3所示。這些程序集中在混凝土徐變變形的標(biāo)準(zhǔn)模型上，因此沒(méi)有考慮到環(huán)氧基樹(shù)脂的蠕變影響。用這種方法確定開(kāi)裂彎矩，因?yàn)榭箯垙?qiáng)度和混凝土的設(shè)計(jì)收縮變形要求直接估算開(kāi)裂彎矩，而不是通過(guò)實(shí)驗(yàn)測(cè)得的。每根梁的跨中長(zhǎng)期繞度在加載后每時(shí)每刻，都能被預(yù)測(cè)出來(lái)，實(shí)驗(yàn)示數(shù)在這里被記錄