变温度场下CFRP布加固工字钢梁疲劳性能研究

为研究湿热环境下CFRP布加固工字钢梁的加固效果,采用有限元软件ABAQUS进行了变温度场下未加固、一层、三层和五层CFRP布加固工字钢梁的数值模拟,得到了工字钢梁的荷载-温度曲线和疲劳寿命-温度曲线,建立了CFRP布加固工字钢梁的疲劳寿命预测模型.结果 表明,CFRP布加固工字钢梁的承载力和疲劳性能受温度的影响,一层、三层、五层CFRP布加固工字钢梁的疲劳寿命增强比例最大分别为157％,266％,370％,极限荷载增强比例最大分别为2.31％,5.53％,8.41％.     

CFRP加固非对称工字钢梁的有限元分析

基于有限元分析软件ABAQUS,分别对CFRP布和CFRP板加固非对称工字钢梁的综合力学性能进行数值模拟,对比分析了未加固梁、外贴CFRP布以及外贴CFRP板3种情况下,不同截面尺寸工字钢梁的承载力和变形。计算结果表明:上下翼缘宽度比为1.6的工字钢梁加固后屈服荷载提升比例最高,宽度比为1.5的工字钢梁极限荷载提升比例最高;外贴CFRP布时,工字钢梁屈服之前的刚度无明显变化,屈服之后刚度提高显著;外贴CFRP板时,工字钢梁屈服前后刚度都显著提高;外贴CFRP布和CFRP板都能极大限制工字钢梁的变形。     

CFRP加固钢筋混凝土梁抗裂、刚度等正常使用性能试验研究

采用CFRP加固钢筋混凝土梁是一种有效便捷的加固方法,其在实际工程中的应用日益广泛,但是近年来大多的研究集中在加固后结构的极限承载能力方面.本文通过5根钢筋混凝土梁(1根对比梁,4根加固梁)的试验,研究了加固梁正常使用荷载下的刚度、裂缝形态和挠度等使用性能.试验结果表明,采用CFRP加固后,钢筋混凝土梁正常使用荷载和截...     

带端部锚具碳纤维复材板加固开裂钢梁的界面剥离规律研究

黏接界面是碳纤维增强复合材料(CFRP)加固钢结构的最薄弱环节,尤其是钢梁缺陷处黏接层易开裂导致加固结构的破坏。对带端部锚具的CFRP加固开裂钢梁进行静载和疲劳试验,记录了试验过程中钢梁裂纹尖端开裂和胶层剥离情况。试验结果表明:静载作用下,界面剥离发生在跨中裂缝处并向两端延伸,端部锚具防止了CFRP板的通长剥离;端部锚具进一步提高了加固梁的极限承载能力,有利于提高加固梁的安全性;疲劳荷载作用下,界面剥离扩展速率在纯弯段基本不变,在弯段外加速扩展;静载作用下,钢梁腹板裂纹尖端开裂过程较缓,具有明显的塑性变形阶段,而疲劳荷载作用下裂纹尖端开裂则呈现突发性。     

温度-荷载耦合作用下端锚CFRP加固RC梁受弯性能研究

为研究端部锚固对碳纤维增强聚合物(CFRP)加固钢筋混凝土(RC)梁高温性能的影响,进行了温度和荷载耦合作用下带有端部锚固的CFRP加固梁受弯性能试验,采用纯外贴、钢压板锚固和自锁式锚固等不同端锚形式,对比分析端部锚固措施对加固梁受弯性能的影响。结果表明：与纯外贴CFRP加固梁相比,端部锚固提高了加固梁常温及高温下的受弯性能;钢压板锚固在常温下可以有效限制CFRP端部剥离,CFRP强度利用率由43.6%提高至79.3%,极限荷载提高12%左右;但是温度达100℃后钢压板锚固无法限制CFRP剥离,承载力退化至未加固水平,加载过程中最大强度利用率只有50.5%;自锁式锚固法在任何温度下均可限制CFRP剥离,其破坏形式多为CFRP拉断,可以最大限度地提高CFRP强度利用效率;在试验温度100℃下极限荷载相比纯外贴形式的提高了22.7%,在试验温度120℃下极限荷载相比钢压板锚固试件仍提高10%。引入了承载力退化系数,给出了温度-荷载耦合作用下端锚CFRP加固梁正截面受弯承载力计算公式,计算结果与试验结果吻合较好。     

表层嵌入预应力碳纤维筋混凝土梁抗弯试验研究

为了充分发挥碳纤维增强塑料(CFRP)筋的高强性能,更有效提高加固梁的力学性能,通过在混凝土梁受弯区表层开20 mm×20 mm的槽后,对直径为7 mm的CFRP筋施加不同水平的预应力并嵌入开好的槽中,并用专用结构胶填充槽道,待结构胶固化后进行加固梁的抗弯试验。通过对9根表层嵌入预应力CFRP筋加固梁和1根未加固梁的抗弯加载试验,初步研究了加固梁的刚度、特征荷载、延性及梁的裂缝发展与破坏模式。研究表明,预应力CFRP筋的高强性能得到充分发挥,加固梁的刚度显著提高,开裂荷载最大提高了303.17%,极限承载能力最大提高237.92%,延性基本能满足抗震要求,破坏模式表现为3种形式。     

端部锚固CFRP板加固RC梁IC剥离过程非线性分析1

端部锚固预应力碳纤维增复合板(Carbon Fiber Reinforcement Polymer Laminate,简称CFRP板)加固钢筋混凝土结构目前最为常见的抗弯加固方式,为探讨端部锚固CFRP加固RC梁IC剥离过程的起始和演化,文章基于部分黏结作用复合梁理论,利用内聚力开裂模型模拟界面层的剥离过程,通过引入含残余强度的四线性黏结滑移本构模型模拟CFRP板与钢筋混凝土梁之间相对滑移带来的界面的变形协调和应力变形行为的非线性特征和软化特性,得到单一裂缝模式下中间裂缝剥离过程中相应的界面黏结剪应力,相对滑移量、CFRP板轴力分布以及加固构件整体荷载 跨中位移,荷载 跨中CFRP板应变的响应曲线,并与文献提供的试验数据进行对比。结果表明,理论计算结果与试验结果基本一致,可以反映端部锚固CFRP板加固混凝土梁的实际受力状态,为端部锚固CFRP板加固混凝土梁的受力分析和设计提供了理论参考。     

锚固装置对碳纤维布抗剪加固钢筋混凝土T型梁承载力的影响

通过对带锚固装置碳纤维加强材料(CFRP)抗剪加固钢筋混凝土梁进行试验研究。共测试6根梁,其中1根为控制梁,1根为U型CFRP箍加固梁,其余4根均为带端部锚固装置的U型CFRP箍加固梁。基于试验结果,首先从破坏模式、抗剪效果等方面分析不同类型锚固装置对碳纤维布抗剪加固钢筋混凝土梁的影响;并将试验结果与GB 50608—2010《纤维增强材料建筑工程应用技术规范》中抗剪承载力计算式进行对比,讨论该计算式的不足。     

预应力CFRP格栅与高性能水泥基复材加固混凝土梁抗弯性能试验研究

为获得预应力CFRP格栅与高性能水泥基复材加固钢筋混凝土梁抗弯性能,将CFRP格栅预应力张拉值、CFRP格栅层数作为试验变量,共设计7根预应力CFRP格栅与高性能水泥基复材加固钢筋混凝土梁,开展其抗弯性能试验研究,分析各变量对预应力CFRP格栅与高性能水泥基复材加固混凝土梁弯曲性能的影响。试验结果表明,由于未进行有效的锚固,CFRP格栅与高性能水泥基复材复合层与混凝土间大部分发生相对滑移现象,大部分加固层为端部剥离破坏,其中CFRP格栅与高性能水泥基复材没有发生脱黏现象。随着CFRP格栅预应力张拉值、CFRP格栅层数的增大,加固梁的抗弯承载力得到显著提高。与未加固的普通混凝土梁相比,加固梁的开裂、屈服和极限荷载有了一定幅度的提高,为未来预应力CFRP格栅与高性能水泥基复材加固混凝土梁端部进行有效锚固提供了一定的依据。     

粘钢加固混凝土梁疲劳性能试验研究

为研究粘钢加固混凝土梁的疲劳性能,进行了2根粘钢加固梁及1根对比梁的疲劳试验。试验研究表明:在钢板与混凝土粘结完好的情况下,粘贴钢板加固较大地提高了梁的抗变形能力;与未加固梁相比,因钢板端部粘结失效,加固梁主筋断裂时的疲劳循环次数反而减少,也说明在粘贴钢板加固工程中,应注意保证钢板端部的良好锚固,使钢板与混凝土良好粘结,钢板才能充分发挥作用。     

Flexural behavior of strengthened steel–concrete composite beams by various plating methods

The effect of pre-intermediate separation on the flexural behavior of strengthened steel–concrete composite beams by either adhesively bonded carbon fiber reinforced polymers (CFRP) sheet or welded/bonded steel plate was studied. In the case of strengthened by CFRP sheet, two different attachment patterns, namely, CFRP sheet wrapped around the flange of the I-beam and CFRP sheet wrapped around the flange along with a part of the web, were examined by testing four different strengthened steel–concrete composite beams under four point bending (4PB). Two of these beams were strengthened by fully bonded CFRP sheet with the two different patterns, while, the others are similar but have pre-intermediate debonding area of 50 mm length × flange width at the bottom surface of the lower flange. In the case of strengthened by steel plate, three different attachment patterns of steel plate to the soffit of the beams, namely, discontinuously welded, end welded, and bonded/welded steel plates, were also tested under 4PB.The experimental results showed that, there is no growth of the intermediate debonding before the yield of the lower flange occurred for all strengthened beams by CFRP sheet. After yielding, the beams with pre-debonding area showed lower flexural capacity than those with fully bonding due to the rapid growth of the intermediate debonding. On the other hand, there is a difference in the yield load between the three different patterns of the welded steel plates with a marginal difference in the elastic stiffness.     

预应力碳纤维复合板加固钢筋混凝土梁的抗弯响应预测

现有的试验研究显示,碳纤维复合材料用量不同时,采用预应力碳纤维复合板加固钢筋混凝土梁可能出现3种弯曲破坏模式(包括受压破坏、受拉破坏、剥离破坏)。基于应变和力平衡的协调性,提出理论公式对3种破坏模式下的名义抗弯强度进行预测。当出现剥离破坏时,提出预应力碳纤维复合板中的受拉应变的极限。此外,考虑预应力碳纤维复合板的作用,提出开裂弯矩、裂缝宽度和加强梁的挠度计算方法。对5根采用预应力碳纤维复合板加固的钢筋混凝土梁进行试验,并通过非线性有限元分析验证所提出的理论公式。同时,预测值与其他研究者的试验结果也进行了比较。     

负载下碳纤维与钢板复合加固钢筋混凝土梁抗弯承载力研究

碳纤维与钢板复合加固钢筋混凝土梁是一种新型的加固方法。通过对1根原梁和6根不同方式加固梁进行的抗弯性能对比试验表明,复合加固对提高抗弯承载力和延性均优于碳纤维和粘钢加固,且初始荷载对其抗弯承载力影响不大。此外,根据试验结果分析了复合加固梁的破坏模式和提高抗弯承载力的限值,分析表明:复合加固梁的抗弯承载力要远远超过混凝土加固规范规定的40%提高幅度限值的要求,且复合加固还能满足其使用性能。因此,对于需要提高较大幅度抗弯承载力且满足使用性能的受弯构件,当负载较大时建议采用复合加固。     

Ferritic stainless steel tubular members strengthened with high modulus CFRP plate subjected to web crippling

Web crippling failure of ferritic stainless steel tubular structural members could be found due to localised concentrated loads or reactions. This paper reports experimental and numerical investigation on strengthening of ferritic stainless steel tubular members using externally bonded high modulus carbon fibre-reinforced polymer (CFRP) plate. The CFRP plate strengthening is only applied to a small localise area subjected to concentrated load. A series of tests on CFRP strengthened ferritic stainless steel square and rectangular hollow sections subjected to web crippling was conducted. The web crippling tests were conducted under four loading conditions of end-two-flange (ETF), interior-two-flange (ITF), end-one-flange (EOF) and interior-one-flange (IOF). A total of 37 web crippling tests was conducted in this study. The investigation was mainly focused on the effects of web slenderness of ferritic stainless steel tubular sections on CFRP strengthening against web crippling. The tests were performed on five different sizes of square and rectangular hollow sections. The ferritic stainless steel type EN 1.4003 test specimens were used in this study. Tensile coupon tests were conducted to determine the material properties of the ferritic stainless steel specimens. Most of the strengthened specimens were failed by debonding of CFRP plate from the ferritic stainless steel tubes. Two different failure modes were observed in the tests of the strengthened specimens, namely the adhesion failure as well as the combination of adhesion and cohesion failure. Finite element models have been developed and verified against the test results. The failure loads, failure modes and the load-web deformation behaviour of the ferritic stainless steel sections are also presented.     

有弱界面的CFRP抗弯加固中U型箍防剥离研究

锈蚀钢筋混凝土梁置换保护层或直接粘贴CFRP加固时,可能因新老混凝土结合面或锈胀裂缝产生水平削弱面。设计了9根加固梁,研究弱界面对CFRP剥离的影响及传统U型箍约束的有效性。结果发现,2种弱界面均使加固梁的整体受力性能受到削弱,局部剥离破坏更易发生,且界面越弱,剪切传递能力越差。U型箍约束能够防止纵向CFRP发生脆性剥离破坏,保证其有效参与受力。然而弱界面仍有可能导致局部保护层剥离,纵向CFRP易过早拉断。实际应用中,宜适度降低纵向CFRP的容许拉应变,并采取更为严格的约束和锚固措施。     

Numerical simulation of steel-plate strengthened concrete beam by a non-linear finite element method model

Strengthening with epoxy bonded steel plate is one of the most widely used techniques for flexural upgrading of reinforced concrete (RC) beams. However, debonding failure at the plate cut-off zone and or in the vicinity of flexure and shear cracks leads to catastrophic failure of the upgraded beams. This particular failure depends on several factors such as the distance of plate curtailment from the support, plate thickness and the provision of end anchors. Since the conventional beam theory cannot predict the debonding failure of such beams, a finite element model capable of predicting the overall behavior of strengthened beams including different failure modes accurately is developed. This paper presents the formulation of finite elements and material models and simulation results of some RC beams tested for flexural strengthening with epoxy bonded steel plates.     

碳纤维布加固钢筋混凝土短梁受弯试验及承载力计算

通过11根不同跨高比碳纤维（carbon fiber reinforced polymer, CFRP）布加固钢筋混凝土梁的受弯试验,研究了跨高比、纵筋配筋率和CFRP布层数对钢筋混凝土梁极限荷载的影响。结果表明：CFRP布加固钢筋混凝土梁的受弯破坏主要有CFRP布拉断和受压区混凝土压碎两种模式;随跨高比的减小,CFRP布加固钢筋混凝土梁极限荷载显著增加;随纵筋配筋率和CFRP布层数的增加,CFRP布加固钢筋混凝土梁极限荷载显著提高。结合文中和已有文献的试验结果,提出了反映跨高比影响的CFRP布加固钢筋混凝土短梁受弯承载力计算方法,该方法既可用于CFRP布加固的钢筋混凝土短梁也可用于浅梁的受弯承载力计算。     

预应力碳纤维布加固钢筋再生混凝土梁受弯承载力研究

试验浇筑4组再生粗骨料掺量为0%、40%、70%、100%的钢筋再生混凝土梁,根据预应力碳纤维布拉断破坏和剥离破坏的界限加固量,每组对2根钢筋再生混凝土梁进行预裂破坏后,分别进行预应力碳纤维布一层和两层加固,然后对4组钢筋再生混凝土梁进行受弯承载力试验。试验表明：随着预应力碳纤维布加固量的增大,加固梁的受弯承载力增大,梁屈服时,纯弯段受拉区横向裂缝数量增多且宽度较小;随着再生粗骨料掺量的增大,加固梁受弯承载力降低,梁屈服时,裂缝数量减少、宽度增大。最后依据试验结果与平截面假定,结合再生粗骨料掺量对钢筋再生混凝土梁受弯承载力的影响,考虑钢筋再生混凝土梁的二次受力,建立了预应力碳纤维布加固钢筋再生混凝土梁的受弯承载力计算公式。计算结果表明：受弯承载力计算值与试验值吻合较好,可以为预应力碳纤维布加固钢筋再生混凝土梁设计提供参考。     

碳纤维增强复合网格-聚合物水泥砂浆加固RC梁的抗弯性能试验研究

为研究碳纤维增强复合(CFRP)网格和聚合物水泥砂浆(PCM)复合加固钢筋混凝土(RC)梁的抗弯性能,对5个RC梁试件进行抗弯性能试验,分析CFRP网格-PCM复合加固RC梁的抗弯破坏机理,研究网格不同层数和不同单位加固量对RC梁抗弯性能的影响。基于抗弯承载力的既有计算模型,引入剥离应变建立改良计算模型,并采用其他学者的9根FRP网格加固RC梁的受弯试验数据,验证改良计算模型的准确性。研究结果表明：CFRP网格-PCM对RC梁的抗弯加固效果明显,单位加固量较高的试件具有更高的承载能力,但其更易发生剥离破坏;在单位加固量相当的条件下,单层网格与双层网格呈现出相同的抗弯性能,双层网格重叠布置的加固方式是有效的;抗弯承载力的既有计算模型对试验结果拟合效果较差,所建立的改良计算模型拟合程度较好,能更好地反映CFRP网格-PCM复合加固层的实际受力状态。     

Flexural strength of steel–concrete composite beams reinforced with a prestressed CFRP plate

Experimental studies have reported that externally-bonded carbon fibre reinforced polymer (CFRP) plate can effectively improve the stiffness and strength of steel–concrete composite beams. This paper presents an analytical solution developed to calculate the flexural strength of strengthened composite beams. The solution assumes certain failure modes and varies the locations of the neutral axis. Non-linear finite element (FE) method was also used to calculate the flexural strength of the strengthened composite beams. Experimental results from literature were employed to validate both the analytical and the FE results. The findings show that the FE analyses are in good agreement with the test data in load–deformation curves. The flexural capacity obtained from the closed-form solution and the FE analyses have a reasonably overall agreement with the experimental results, which demonstrates the present closed-form solution is simple yet accurate. The analyses also show the flexural strength is not influenced by the permanent load and the prestressing force when failure results from rupture of the CFRP plate, but the flexural strength reduces with the permanent load and increases with the prestressing force when failure results from crushing of concrete.