【正文】 另外，由于梁二直到負荷285天后才進行加固，因此兩根梁的干燥徐變假設(shè)相同。同一個最終徐變系數(shù)被用于預(yù)測梁二的最終繞度，并假設(shè)混凝土與碳纖維貼片之間的粘結(jié)層沒有蠕變。這種差異也與觀察到的梁二裂縫較小，梁一具有明顯裂縫的現(xiàn)象相符合（值得注意的是兩跟梁的最大彎矩都是由自重和實施的集中荷載所產(chǎn)生，通過對每根梁的開裂彎矩調(diào)整，該模型的預(yù)測對實驗結(jié)果進行了校核。運用CEBFIP 和 ACI進行繞度分析預(yù)測為了實現(xiàn)與鋼筋混凝土梁和用碳纖維貼片加固的鋼筋混凝土梁實驗結(jié)果相吻合，Hall 和 Ghali便用了分別基于CEBFIP1990年的標準守則和ACI委員會第209號推薦規(guī)范的方法。撓度的分析預(yù)測單從實驗結(jié)果，試圖通過梁的繞度分析預(yù)測來找出任何不明顯的反應(yīng)特征?；谱x數(shù)中的顯著分散，特別是后期數(shù)據(jù)記錄中，被認為是由于應(yīng)變表在讀數(shù)日和反復(fù)重連或測量儀器斷線期間溫度變化所致。他們的結(jié)果顯示相對濕度在5%—50%之間變化，夏季平均相對濕度大約為35%，冬季的平均相對濕度大約為10%。繞度增長率降低時間段與夏季月份相對應(yīng)，徐變增加的時間段與冬季月份相對應(yīng)。 也就是說，初看起來，沒有跡象表明碳纖維布加固能卸載，從而對持續(xù)負載不能起效。梁一早于梁二開裂。繪制時間為加載后2470天。加載后幾個月，在梁二上可以看到細小裂縫從梁跨中開始延伸。如果有一些寬裂紋，F(xiàn)RP條的變形和彎曲應(yīng)力在與混凝土粘結(jié)的FRP條段和FRP條延伸過裂縫段之間有很大的變化。在控制梁上，可以看到很多彎曲裂紋從其受拉區(qū)表面開始擴展，這主要集中在彎矩不變的兩集中荷載作用點之間。每根梁的跨中繞度與自重有關(guān)，也與加載之后一開始和每隔一段時間記錄的碳纖維貼片的縱向滑移量有關(guān)。對于梁二，預(yù)期荷載造成的破壞遠沒那么大，但從長遠來看任然導(dǎo)致值得注意的繞度。這些測量儀表主要用于測量碳纖維貼片末端相對于混凝土粘結(jié)表面的縱向相對位移。測試設(shè)置和步驟簡支梁的支座跨度為3200mm（如圖1）。碳纖維貼片100mm寬，2970mm長。 177。研究結(jié)果強調(diào)，在實踐中環(huán)氧樹脂蠕變可影響玻璃鋼條長期性能的潛力。因此，玻璃鋼條被運用于加固梁，它便受到增加的持續(xù)的荷載，可能最終所受的額外持續(xù)荷載是原始的混凝土和鋼筋所帶來的，而不是玻璃鋼條所帶來的。當(dāng)模型的存在為預(yù)測用玻璃鋼條加固的RC梁的長期變形（例如，Charkas et ），這些模型沒有明確的考慮到環(huán)氧樹脂膠粘劑蠕變。長期撓度的數(shù)據(jù)顯示,碳纖維復(fù)合材料加固的梁的隨時間發(fā)生的蠕變變形占瞬時變形的比例比沒有加固的梁大。Choi et al最近做的試驗說明，當(dāng)加載后7天之內(nèi)，在剪應(yīng)力作用下發(fā)生顯著的蠕變，位于混凝土和玻璃鋼條界面之間的環(huán)氧基樹脂。分析模型已被證實與用玻璃鋼條加固于外表面的RC2和timber3梁的有限的實驗觀測相違背。如果隨后給梁加以持續(xù)負荷，環(huán)氧膠粘劑可能發(fā)生蠕變，也允許玻璃鋼條卸載，使他們不能承受持續(xù)荷載。關(guān)鍵詞：蠕變，撓度，環(huán)氧樹脂粘接劑，纖維增強復(fù)合材料（玻璃鋼），鋼筋混凝土簡介在最近幾年出現(xiàn)了對使用（FRPs）纖維增強聚合物加強現(xiàn)有混凝土結(jié)構(gòu)的大量研究。實驗繞度已經(jīng)和ACI 209R92 and CEBFIP MC 90前期預(yù)估的繞度作了對比。其中一根梁的外部用纖維加固材料條加固，而另一根梁是用來作為對照樣本。specimen. Two CFRP strips were bonded to the tension face of the second beam (Beam 2) using an epoxy adhesive. The strips are 100 mm ( in.) wide, mm ( in.) thick, and 2970 mm ( in.) long. Over the shear spans at each end of Beam 2, GFRP sheets were wrapped in a Ushape to cover the two side faces and the tension face of the beam. The CFRP strips are unidirectional with the fibers aligned along the length of the beam. The strips have a modulus of elasticity of 165 GPa (23,571 ksi) and a tensile strength of 2800 MPa (400 ksi) in the direction of the fibers (manufacturer’s data). Test setup and procedureThe beams were simply supported (pinroller) over a span of 3200 mm ( in.) (Fig. 1). The midspan deflection due to selfweight was recorded using a dial gauge (least count mm [ in.]) mounted on a lightweight steel frame over the 3200 mm ( in.) span. For Beam 2, electronic spring gauges were mounted on the concrete adjacent to each end of one of the CFRP strips. The deflected tip of the spring gauge was carefully positioned to touch the exposed end of the CFRP strip. These gauges were designed to record the longitudinal slip of the ends of the CFRP strip relative to the concrete to which the strip is bonded. Each beam was then loaded in fourpoint bending by applying twopoint loads (each kN [ kips]) at a distance of 930 mm ( in.) from each support. This level of loading was designed to push both beams into their working range. For Beam 1, the load was expected to result in significant cracking of concrete in the tensile zone, but stresses in the concrete in pression and steel in tension would remain elastic. In Beam 2, the load was expected to cause far less damage but still result in significant deflections over the long term. The loads were provided by hanging concrete blocks on load hangers bearing on the upper surface of each beam. The loads were transferred to the beams by gradually lowering the blocks onto the beams using hydraulic jacks. The hydraulic jacks were then removed. The midspan deflection of each beam relative to the selfweight value as well as the relative slip movements for the CFRP strip were recorded immediately after loading and at regular intervals thereafter. Data were recorded several times during the first 24 hours of loading, daily for the first month after loading, increasing to every 3 days, weekly, biweekly and, finally, greater intervals. The loaded beams are located in the airconditioned basement level of a laboratory building where the average temperature is expected to remain relatively constant with time.Experimental results and discussionUpon loading, the immediate midspan deflections of the beams relative to the measured selfweight deflections were and mm ( and in.) for the control and CFRPstrengthened beams, respectively. Numerous flexural cracks were observed extending from the tension face of the control beam, predominantly over the region of constant bending moment between the point loads. No flexural cracks were observed in Beam 2 at first loading. Such cracking would be hard to see unless significantly wide, due to the existence of the FRP strips. This is because the tensile strain in the FRP will be constant in the constantmoment section. If there were a few wide flexural cracks, the strain, and thus the stress, in the FRP