预应力碳纤维布加固混凝土板受弯承载力实用方法研究

提出了一种新型实用碳纤维布加固系统,包含首次提出的碳纤维布环氧树脂楔形夹持体夹具、张拉设备和碳纤维布薄层钢板锚具。试验表明,环氧树脂楔形夹持体夹具夹持力强,应力损失低,施工安全,现场安装方便,且易于在工厂加工制作,适合于实际工程批量应用;张拉设备轻便,易于安装,不受构件支承条件影响。采用该新型实用碳纤维布加固系统对混凝土薄板进行的验证性加固试验表明,张拉设备方便适用,工艺流畅;预应力碳纤维布加固后构件工作性能明显改善,开裂前的弹性极限荷载达到未加固对比试件及普通粘贴碳纤维布加固试件的4倍;预应力碳纤维布加固试件的极限承载力比未加固试件提高103%,比普通粘贴碳纤维布加固试件提高32%,承载力明显提高。碳纤维布直至断裂也未从薄层钢板锚具中滑出,验证了其良好的锚固性能。     

碳纤维布加固木柱轴心抗压性能试验研究

采用碳纤维布,对8组木柱(短柱)构件进行环向粘贴碳纤维布加固。通过试验考察了碳纤维布加固对木柱轴心抗压极限承载能力的提高效果;分析了碳纤维布加固木柱的破坏形态及荷载应变关系;通过各组试件试验结果的对比分析了碳纤维布的用量、布置形式对提高轴心抗压承载力的影响。     

反拱法加固混凝土受弯构件理论及试验研究

对采用反向起拱粘贴碳纤维布加固混凝土梁构件的基本原理和设计方法进行了初步研究,提出了基于预应力原理的反拱法碳纤维布材加固梁构件的施工工艺。在此基础上,进行了3根试件的试验。通过试验结果对比了不同加固工艺的受弯构件的开裂荷载、极限荷载、抗弯刚度等工作性能,分析了反拱加固的预应力效应。试验发现,反拱加固试件的开裂荷载较普通粘贴加固试件的开裂荷载提高了36.2%,屈服条件下的变形减小了24.2%。试验结果表明,采用反拱加固可方便有效地卸除加固构件的残余应力,并产生预应力效应,可充分发挥碳纤维布材料高强度的特性,提高构件刚度和承载能力。     

碳纤维布加固钢结构的黏结性能研究

与传统的钢结构加固方法相比,粘贴碳纤维布加固钢结构具有很大的优势和应用前景,如不会导致严重的应力集中、不会产生残余应力、施工方便、维护费用低等。碳纤维布与钢结构之间的黏结性能直接影响加固效果,但是目前国内对这方面的研究还未涉足。本文对粘贴碳纤维布加固钢板进行了静力拉伸试验,采用高强型和高模型碳纤维布及不同的端部锚固措施,考察了未损伤钢板和损伤钢板加固后的效果。得到了加固试件的屈服荷载和极限荷载,并对不同的破坏形式进行了分析。试验结果表明,粘贴碳纤维布加固能明显提高钢构件的屈服荷载。测量了碳纤维布的应变分布,得到了碳纤维布与钢板之间的黏结应力分布和碳纤维布的有效黏结长度,并与理论公式的计算结果进行了对比,二者吻合较好。     

碳纤维布加固玄武岩纤维复材筋工程用水泥基复合材料混凝土梁的受弯性能

设计制作了三组不同层数的碳纤维布(CFS)加固受弯构件,分别为玄武岩纤维复材(BFRP)筋混凝土梁、BFRP筋工程用水泥基复合材料(ECC)梁和BFRP筋ECC-混凝土复合梁,并对其进行受弯性能试验研究。研究了碳纤维布粘贴层数对加固试件极限荷载、破坏形态、裂缝和变形的影响。结果表明:相同荷载下,复合梁和ECC梁试件的变形和裂缝宽度均小于普通混凝土梁试件。在受弯构件受拉区配置ECC可有效提高构件抵抗变形和裂缝的能力。经粘贴碳纤维布加固后的试件的开裂荷载和极限荷载均大于未加固试件,粘贴一、二、三层CFS加固的复合梁极限荷载较未加固梁分别增加了12. 5%、16. 6%、19. 7%。粘贴CFS布可有效提高构件的承载力和抵抗变形、裂缝的能力。改善效果随CFS粘贴层数的增加而增大,但提升幅度逐渐减小。     

碳纤维布(CFRP)与钢结构粘结性能的试验研究

采用弯拉试验方法对碳纤维布与钢构件粘结性能进行了试验。研究了碳纤维布粘贴厚度、宽度与长度对粘结强度的影响。试验结果表明：随着粘贴厚度的增加,极限承载力逐渐增加,但不是简单的线性关系;随着粘贴宽度与钢试件的宽度比值增加,极限承载力逐渐降低;纤维布与钢结构的有效粘结长度大约在120—150mm之间。     

碳纤维布和钢板在旧桥加固中的应用

介绍采用粘贴碳纤维布和粘贴钢板加固桁架拱的方法，并对其进行了静动载试验，试验结果表明，加固后桥梁的整体刚度和承载力得到了一定程度的提高，说明采用粘贴碳纤维布加固拉弯构件、粘贴钢板加固受压构件的综合加固方法是有效的。     

碳纤维复材布加固不锈钢圆管短柱轴心受压试验研究

为研究碳纤维复材(CFRP)布加固不锈钢圆管短柱轴心受压性能,对外贴CFRP布加固不锈钢圆管短柱进行轴心受压试验。试验共制作了20根构件,4根未粘贴CFRP布的控制试件,8根环向外贴CFRP布的加固试件和8根正交(环向和纵向)外贴CFRP布加固试件。试件破坏形式主要分为两种:第一种是试件底部产生"象足式"屈曲破坏,第二种是外贴CFRP布加固(环向和纵向)后的试件在中间高度处产生向内局部屈曲变形;同时,在粘贴层数相同的情况下,环向粘贴效果优于正交粘贴效果;在相同的粘贴方式下,粘贴层数越多加固效果越好;纵向碳纤维布的存在反而会降低试件的极限承载能力,但可以略微提高试件的轴向刚度;并且在壁厚一定的情况下,直径越大的不锈钢圆管在CFRP布加固后增强效果越明显。     

碳纤维布粘贴加固BFRP筋-ECC-混凝土组合梁受弯性能研究

工程结构服役期间经常由于使用功能改变或使用荷载增加而需要对结构进行加固改造。为研究经碳纤维布粘贴加固后的玄武岩纤维增强塑料（BFRP）筋-工程用水泥基复合材料（ECC）-混凝土组合梁的受弯性能,对3组共12根不同ECC高度替换率（0、0.29和0.58）的BFRP筋-ECC-混凝土组合梁底分别粘贴1、2和3层碳纤维布的加固构件及未加固构件进行静力受弯性能试验。研究碳纤维布粘贴层数和ECC高度替换率对组合梁受弯承载力和破坏形态的影响。试验结果表明：采用受拉性能优异的ECC替代受拉区部分混凝土形成的ECC-混凝土组合梁不仅可提高构件承载力,还可有效改善构件抵抗开裂和变形的能力;组合梁底粘贴3层碳纤维布,裂缝宽度可降至未加固试件的10%,受弯承载力提高20%,挠度降低50%。借鉴钢筋混凝土理论,基于合理的基本假定和简化的材料本构模型,提出粘贴碳纤维布加固的组合梁受弯承载力计算式,并给出碳纤维布强度折减系数,理论预测值与试验实测值吻合良好。     

粘贴法加固混凝土构件的防火试验研究

试验研究分析了涂不同厚度防火涂料的粘贴法加固混凝土试件在火灾下的耐火极限。试验结果表明,碳纤维布和钢板对试件温度场的影响是相同的,厚涂型钢结构防火涂料对混凝土结构的防火作用明显,防火涂料厚度与防火性能并不成正比。试验确定粘贴法加固混凝土构件防火涂层厚度的最佳取值为40mm。     

碳纤维材料加固钢梁的试验研究

碳纤维材料应用于钢结构加固在实际工程中应用较少 ,缺乏理论与试验支持。介绍了各种碳纤维材料加固钢结构工字型梁的试验及结果 ,给出了碳纤维布、碳纤维板、钢板等材料的力学性能 ,得出了各种加固方式的承载力及荷载 -位移曲线和工字钢梁截面上实测的应力、应变。研究成果可供工程应用参考     

Thermal stress measurement in steel plate strengthened by CFRP and aluminum alloy plates

In steel members strengthened by carbon-fiber reinforced polymer (CFRP) plates, the thermal stresses are introduced in the steel members, the CFRP plates and the adhesive layers when temperature changes because the linear thermal expansion coefficients of steel and CFRP are mismatched. As so far, the authors proposed a technique to reduce the thermal stress in steel members strengthened by CFRP plates, which involves bonding aluminum alloy plates with CFRP plates. In the proposed method, the thermal stress in steel member can be reduced so that there are negligible levels of stress in steel member when the cross sectional areas of CFRP and aluminum plates are designed to correspond to the coefficient of thermal expansion of steel, even though the thermal stresses are introduced in the CFRP and aluminum plates. In this study, to confirm the maintaining the thermal stress reduction in steel member by proposed method, thermal stress measurement in steel plate strengthened by CFRP and aluminum plates was carried out about 21 months. In this research, the thermal stress introduced in the steel plate strengthened by CFRP plates was also measured. Furthermore, to assume the thermal shear and normal (peel) stresses in adhesive layers, FE analysis with plane stress element was employed. As the result, it was shown the thermal stresses in steel plate with CFRP plate were able to calculate by using composite theory and measured temperature. Furthermore, in steel plate strengthened by CFRP and aluminum plates, the thermal stress introduced in steel plate was negligible-small through the all-season. It was found the thermal stresses in steel plate with CFRP plates as well as CFRP and aluminum plates were also estimated by using composite theory and measured temperature. In the steel plate strengthened by CFRP and aluminum plates, the thermal shear and normal stresses in adhesive layer glued to steel plate become smaller than that in the conventional CFRP bonded specimen. However, the shear stress in adhesive layers between CFRP and aluminum plates in proposed method was higher than the thermal stress in adhesive layers between CFRP plates in conventional method.     

CFRP加固工字钢梁的结构性能和失效分析

针对碳纤维加固聚合物(CFRP)失效分析和CFRP加固工字钢梁的结构性能进行了试验和数值模拟。了解CFRP的失效模式有助于防止和减缓结构破坏。对1根未加固梁和12根使用不同类型、尺寸CFRP条带加固的梁进行了试验和数值模拟。试验采用静态逐步加载的四点弯曲法,并利用ANSYS软件对试样进行3D建模和非线性分析。结果显示,用于工字钢梁加固的CFRP失效模式包括:集中荷载处开裂(BS)、集中荷载处脱粘(BD)、端部分层(EDL)以及端部脱粘(ED)。CFRP失效模式的产生和发展取决于强化进度。研究发现,不同加固规格的CFRP加固钢梁的结构性能不同。     

碳纤维布加固钢结构疲劳试验研究

钢构件疲劳损坏是钢结构破坏的主要形式之一 ,通过对拉 -拉应力状态下碳纤维布加固钢结构K形焊缝疲劳性能的试验研究与分析 ,认为在钢构件焊缝部位粘贴碳纤维能够有效降低焊趾处的应力集中 ,明显改善钢构件的疲劳性能 ,从而延长钢结构疲劳构件的使用寿命 ,具有很高的应用价值。     

变刚度双向板内力的能量法计算

体外粘贴碳纤维板 (CFRP)或钢板可有效地加固钢筋混凝土结构 ,使其承载力提高 ,受力性能改善。但外贴CFRP或钢板的混凝土板成为突变刚度板 ,其内力计算较为复杂。基于变分原理 ,应用瑞次能量法给出了该类加固板的内力及挠度的计算公式 ,并在此基础上编制了适用于任意长宽比的外贴板加固混凝土双向板的计算程序 ,以便于实际工程的直接应用。     

碳纤维布加固修复钢结构粘结界面受力性能试验研究

采用粘贴碳纤维增强复合材料技术对损伤钢结构进行修复 ,可以有效地恢复结构承载力。通过试验和解析方法对粘贴碳纤维布加固修复钢结构技术的粘结界面受力性能进行了分析 ,提出粘结界面剪切应力的计算公式 ,并在实际算例中取得了与试验较为吻合的结果 ;同时 ,初步探讨了不同粘贴参数对复合构件粘结界面应力的影响 ,为实际结构的加固修复提供了理论依据     

CFRP加固圆形钢管抗压承载力研究

以碳纤维增强复合材料(CFRP)加固长圆形钢管轴心受压试验结果为基础,分析了CFRP在加载过程中的力学行为并提出了CFRP的破坏与加固机理。考虑初偏心、材料和几何非线性的影响,建立了一个预测承载力、轴向和横向位移的纤维模型,分析了CFRP的有效抗压弹性模量与CFRP层数的变化关系。将有效抗压弹性模量应用于有限元模型中进行加载试验模拟,验证简化纤维模型的合理性。结果表明:在达到极限承载力之前,圆形钢管轴心受压构件中部全截面均表现为压应变,验证了提出的加固机理; 随着CFRP层数的增加,CFRP的有效抗压弹性模量按自然对数增长; 有效抗压弹性模量的引入较好地模拟了CFRP加固钢管的受压机理,并且纤维模型计算结果与有限元模型计算结果吻合良好; 随着加载偏心距增大,CFRP对长轴压构件承载力的贡献率逐渐降低,因此对于此类加固构件的使用应该尽量减小加载偏心距,以充分利用CFRP的抗压强度。     

CFRP加固含混合型边裂纹钢板的疲劳性能试验研究

为研究碳纤维增强复合材料(CFRP)对含初始边裂纹钢板疲劳性能的改善效果,使用MTS试验机对未加固及CFRP材料加固后的含边裂纹钢板进行疲劳试验,比较了裂纹形式、钢板初始损伤度、CFRP粘贴面以及CFRP材料种类(CFRP布与CFRP板)对钢板疲劳寿命的影响.共设计制作了3个未加固试件、3个CFRP布双面加固试件、3个...     

Compressive behavior of circular CFST columns externally reinforced using CFRp composites

Over the last several decades, various approaches to strengthening steel structures through the use of Carbon fibre reinforced polymer (CFRP) composites have been investigated; however, most of the studies have been focused on the steel tubes. This paper presents the feasibility analysis on the application of CFRP composite strips to strengthen the CFST column member under axial loading. CFRP strips having a width of 50 mm were used to confine the columns. The experimental parameters were the spacing between the CFRP strips (20 and 30 mm) and number of CFRP layers (one, two and three layers). All columns were tested under axial compression until failure. The experimental results revealed that bonding of CFRP composites effectively delayed the local buckling of the columns and also reduced the axial deformation by providing a confinement/restraining effect against the elastic deformation at both spacings. The confinement effect provided by CFRP composites was increased with the increase in the number of layers; however, the enhancement in buckling stress was not proportional. The load carrying capacity of the column increased with the application of CFRP strips, by up to 30% compared to the of un-strengthened column. From the test results it is suggested that the application of CFRP strips at a spacing of 20 mm or 30 mm is suitable for strengthening of a CFST circular column member; however, the application of strips at intervals of 30 mm recommended as an economical approach to strengthening compared to the 20 mm spacing. Finally, an analytical equation was proposed to predict the load carrying capacity of the CFRP strengthened CFST column, and the average difference between the calculated and experimental value was only ±5%.     

Strengthening of prestressed concrete girders with composites: Installation,design and inspection

The application of fibre reinforced polymer (FRP) or steel reinforced polymer (SRP) materials to the tension side of a reinforced/prestressed concrete member has been accepted as a strengthening technique to increase the load carrying capacity and in some cases can enhance member serviceability. Proper installation and regular inspection of a composite (FRP or SRP) strengthening system is important since quality of the bond is essential to internally transfer forces. This paper describes an experimental programme conducted to study the behaviour of six prestressed concrete bridge girders, which were tested under static and fatigue loading conditions. The test results were combined with the results of 16 other girders tested by the authors to develop structural design guidelines and guidelines on the installation and inspection of composite strengthening systems. The behaviour was also examined using value engineering to evaluate the cost-effectiveness by investigating the overall system performance. Research findings indicate that SRP materials are more structurally efficient than carbon FRP (CFRP) materials. The results of an inspection demonstration programme, including the pull-off testing of over 150 CFRP samples, has shown that the most effective inspection techniques are visual inspection, pull-off testing, and acoustic sounding.