CFRP加固焊接钢结构的疲劳性能试验研究

由于焊缝自身的缺陷,导致大部分焊接钢结构是由于焊接接头的疲劳断裂而失效。碳纤维增强复合材料(CFRP)加固焊接钢结构应用研究较少,尤其是焊接构件加固之后的疲劳性能的试验和分析。通过试验和计算对比,定量分析对接焊Q345钢板在采用CFRP布加固前后的疲劳性能的改善,并基于BS7608标准,采用有限元软件ANSYS对CFRP布加固焊接Q345钢板进行受力分析,运用S-N曲线预估构件加固后的疲劳寿命。结果表明:CFRP布加固可有效增大焊接钢构件的疲劳寿命;合理修正S-N曲线后,可较准确的预估构件加固后的疲劳寿命。此次研究得到了较准确的结果,对焊接钢构件采用CFRP布加固后疲劳寿命的设计有参考意义。     

CFRP加固焊接钢结构力学性能研究

当前焊接钢结构在工程中大量使用,由于钢结构焊接中存在的缺陷,钢结构或构件在远未达到强度极限时就发生破坏或不能正常工作,导致钢结构达不到设计的预期使用寿命,甚至于远远没有达到预期服役年限,引发了一系列的工程破坏事故。通过分析、统计发现,疲劳是钢结构破坏的主要形式之一,通过对静栽拉伸状态下碳纤维布加固钝形焊缝力学性能试验的分析与研究发现,碳纤维布能够显著提高焊接构件的抗拉极限与使用寿命,并降低焊缝处的应力集中。     

CFRP加固焊接钢结构力学性能研究

当前焊接钢结构在工程中大量使用,由于钢结构焊接中存在的缺陷,铜结构／构件远未达到强度极限时就发生破坏或者不能正常工作,导致钢结构达不到设计的预期使用寿命,甚至于远远没有达到预期服役年限．引发了一系列的工程破坏事故。通过分析、统计发现其中疲劳是钢结构破坏的主要形式之一,本文通过对静载拉伸状态下碳纤维布加固钝形焊缝力学性能试验的分析与研究,发现碳纤维布能够显著提高焊接构件的抗拉极限与使用寿命,以及降低焊缝处的应力集中。     

碳纤维增强钢构件的滞回性能分析

以有限单元法和钢结构稳定理论为基础,运用ANSYS有限元软件进行计算与分析,研究碳纤维对受循环荷载作用的钢构件的增强作用.研究发现:轴压比是影响受压钢构件滞回性能和碳纤维使用效果的重要因素;增强后钢构件的循环水平极限荷载和位移延性会随着碳纤维用量的增长而增大.粘贴碳纤维能够有效地提高钢构件的承载力,改善钢构件的延性,提高其抗震性能.     

碳纤维增强钢构件的动力稳定性分析

研究碳纤维对受动荷载作用的钢构件的增强作用。以有限单元法和钢结构稳定理论为基础,运用大型ANSYS软件进行计算与分析。计算与分析结果是碳纤维增强后的钢构件,其承受动载能力和位移延性的提高程度随着碳纤维用量的增长而增大。粘贴碳纤维能够有效地提高钢构件的承受动载力,改善钢构件的延性,提高其抗震性能。     

钢结构疲劳修复及延寿研究进展

承受交变荷载作用的钢结构构件在发生疲劳破坏时往往没有明显的征兆,极易造成巨大的经济损失和重大人员伤亡。因此,如何有效地提升钢材及钢结构构件的疲劳性能、延长其疲劳寿命,一直受到国内外学者的高度重视。在全面回顾国内外钢结构疲劳修复与延寿技术现状和进展的基础上,重点介绍了冷喷涂技术及其应用于钢结构疲劳修复与延寿的研究现状和最新进展,认为选择合适的冷喷涂工艺参数和冷喷涂粉末在钢构件表面制备性能优异的涂层可以有效地提高钢结构构件的疲劳性能。在总结现有成果的基础上,并结合在冷喷涂提升钢材疲劳性能方面的研究成果和经验,指出冷喷涂技术在应用于钢结构疲劳修复与延寿方面有较大的应用潜力,但当前冷喷涂层和钢基体的结合机理、二者的协同受力与变形行为以及疲劳断裂机制等相关理论亟待完善,挖掘适合于钢结构工程的冷喷涂技术的应用场景和技术体系是该技术在钢结构疲劳修复与延寿领域的主要发展方向。     

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。     

碳纤维片加固在钢框架结构中的应用与效果评估

本研究旨在评估碳纤维技术（CFRP）在钢框架结构加固中的应用效果及其可行性。鉴于钢结构在建筑领域中广泛应用同时面临腐蚀和疲劳裂纹等挑战,本文探索了碳纤维作为一种新型加固材料的潜力。研究以碳纤维的物理化学特性及其在钢框架加固中的应用方法和施工细节为出发点,通过采用静态加载测试、动态响应分析和长期耐久性测试等方法,全面量化了碳纤维加固对钢结构强度、延展性和耐久性的改善效果。研究结果表明,碳纤维加固技术显著提高了钢框架结构的性能,其中包括结构的强度、延展性和耐久性的显著提升。基于这些发现,本研究得出结论,碳纤维加固技术能显著提高钢结构的性能,展示了广阔的应用前景。     

Q460D高强钢及其焊缝连接疲劳性能试验研究

在疲劳荷载作用下钢结构焊缝区易发生疲劳断裂,通过Q460D高强钢及其焊缝连接的疲劳性能试验研究,结合试验数据,拟合了Smax-N曲线预测其疲劳寿命,根据疲劳损伤理论分析了疲劳破坏程度,并通过断口形貌揭示了疲劳裂纹扩展规律。研究结果表明：Q460D母材具有较高的疲劳抗力;对接焊缝接头Smax-N的95%保证率曲线与ANSI/AISC 360-10的疲劳设计曲线吻合较好;GB 50017—2003的设计曲线能较好预估循环次数大于40万次以上十字接头的疲劳寿命。损伤指标能够较好地表征疲劳破坏过程中构件内部状态的变化,缺口系数越大,损伤发展越快。瞬断前裂纹扩展规律与损伤发展一致,随着损伤发展疲劳条带间距逐渐变大。     

钢结构构件疲劳破坏的研究分析

对钢结构的疲劳问题进行研究,分析了引起钢结构疲劳破坏的原因,从而总结出提高和改善钢结构构件疲劳性能的设计、施工等措施,达到尽量避免钢结构构件疲劳破坏的目的。     

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加固疲劳损伤钢结构的断裂力学分析

金属结构,特别是承受反复荷载作用的在役钢结构,通常存在不同程度的缺陷和疲劳损伤。在钢结构的损伤部位粘贴FRP对其疲劳损伤进行加固具有很多优势。对含中央疲劳损伤裂纹钢板粘贴CFRP加固,改善其剩余疲劳寿命进行了理论分析。基于线弹性断裂力学理论,采用有限元计算模型对裂纹前端的应力强度因子进行了计算。并根据Paris_Erdogan裂纹扩展模型,计算了加固前后疲劳损伤钢板的剩余疲劳寿命,验证了这一加固方法的有效性。     

碳纤维增强材料(CFRP)加固钢梁的疲劳试验研究

以钢梁为研究对象,对未加固钢梁与碳纤维增强材料CFRP加固钢梁在应力幅较小的中高周疲劳试验中的不同疲劳寿命进行对比,并对疲劳试验结果进行拟合分析。结果表明,在钢梁下翼缘疲劳敏感区域粘贴CFRP可以有效提高钢梁的疲劳寿命,对于存在初始疲劳裂缝的钢梁,采用CFRP加固可以将疲劳损伤钢梁的疲劳寿命恢复到未损伤钢梁的水平。     

外贴CFRP板加固锈蚀钢板疲劳性能试验研究

为研究外贴CFRP板对锈蚀钢板疲劳性能的影响,开展16个CFRP板加固锈蚀钢板试件的疲劳拉伸试验,研究锈蚀程度、CFRP刚度、CFRP预应力度、端部锚固及疲劳应力幅对CFRP板加固锈蚀钢板疲劳破坏模式、疲劳寿命及裂纹扩展规律的影响。研究结果表明,外贴CFRP板可以显著提升锈蚀钢板疲劳寿命,对质量损失率为9.38%、13.39%、16.61%及21.24%的锈蚀钢板,端部锚固条件下双面粘贴CFRP板加固试件疲劳寿命相对于未加固试件分别提高了18.4倍、9.3倍、8.9倍及11.4倍;加固方式对疲劳加固效果影响显著,端部锚固可以有效延缓黏结界面失效,增大CFRP板加固刚度或采用预应力加固均可显著降低裂纹扩展速率。     

碳纤维布加固钢筋混凝土受弯构件的疲劳性能研究

进行了两种不同应力水平下碳纤维布加固钢筋混凝土板的疲劳试验和普通钢筋混凝土板的疲劳对比试验。试验中对构件进行了从开始到疲劳破坏的全程观测,包括了裂缝的出现和发展,混凝土、钢筋和碳纤维应变变化,构件挠度变化等。试验结果表明,碳纤维对改善受弯构件的抗疲劳性能,延长疲劳寿命很有效。其中粘结胶体性能的好坏对能否充分发挥碳纤维布材料优势有很大的影响。基于平截面假定,指出了构件截面在疲劳过程中应力重分布的规律。     

A comparative study on fatigue behaviour of steel beams retrofitted with welding,pultruded CFRP plates and wet layup CFRP sheets

This paper investigates the fatigue behaviour of defected steel beams retrofitted with three different methods, i.e., welding, welding and bonding with CFRP plates or CFRP woven sheets laminated via a wet lay-up process. Two different types of CFRP materials and two types of epoxies were selected in this study. An initial cut was made on the tensile flange in the mid span of each beam. Different failure modes were observed for beams retrofitted with CFRP plates and CFRP sheets. It was found that one layer of CFRP plate and epoxy strengthening system can extend the fatigue life of steel beams about 7 times comparing with beams repaired with solely welding method, while the fatigue life was extended abound 3 times for beams strengthened with 4 layers of CFRP woven sheets. Mean S–N curves were obtained based on the test data, that can be used to predict the fatigue life of steel beams retrofitted with similar CFRP materials. The crack propagation rate was measured using strip strain gauges. The CFRP plates showed better performance in resisting crack propagation than CFRP sheets under fatigue loading conditions. The relationship between the maximum stress and the crack propagation rate could be used to predict the crack length of beams retrofitted with similar CFRP strengthening systems.     

Fatigue of girth butt weld for cast steel node connection in tower structure under wave loadings

The application of cast steel node shows a popular tendency in long‐span space structures. The girth butt welds in the joint are the critical parts under fatigue loading. This study presents a fatigue life evaluation of the girth butt welds for the cast steel node connections, which are in a steel tower structure on an offshore platform under heavy wave fatigue loadings. The refined node FEM model is built including the welds. The random waves are treated as ergodic stationary stochastic process; the node structure is considered as a linear dynamic amplification system to decide its output of the stress amplitude response while the random wave is inputted into the system. The welds are designed as different details of bilateral weld, single‐sided weld with a sleeve, single‐sided weld with a backing plate or without a backing plate. The fatigue life of every weld detail is studied by hot‐spot stress method, and the design of weld detail combination is analyzed. Copyright © 2013 John Wiley & Sons, Ltd.     

CFRP加固钢筋混凝土梁抗弯疲劳寿命研究

CFRP加固作为一种先进的结构加固技术,由于性能优越,在我国工程领域已经得到广泛的应用,我国标准化委员会也已制定了相应的规程来规范并推广这项技术,但由于国内相关研究数据较少,规范中并没有就承受疲劳荷载构件的使用寿命进行规定.文章从钢筋的线弹性损伤理论出发,通过分析国内外相关试验数据定量分析研究了CFRP加固构件的疲劳寿命.通过统计分析,得到了构件内钢筋的S-N曲线,将公式反推得到的数据与现有国内外规范中的数据对比发现,CFRP加固后钢筋的使用寿命明显增加.     

配置碳纤维预应力筋的钢纤维活性粉末混凝土无腹筋梁疲劳性能试验研究

对6根仅配置纵向CFRP预应力筋的钢纤维活性粉末混凝土（RPC）无腹筋梁试件进行了静力和疲劳试验,研究了RPC钢纤维含量、疲劳荷载水平、加载方式等参数对其疲劳性能的影响。结果表明：疲劳荷载作用下梁试件发生剪切破坏;无论是承受静力荷载还是疲劳荷载的梁试件,都不宜过高估计钢纤维的作用而取消抗剪腹筋;提高钢纤维含量可以显著改善梁试件的疲劳性能,钢纤维含量为3%的CFRP预应力筋RPC无腹筋梁,若RPC的主拉应力小于其抗拉强度的50%,可免于疲劳破坏;经回归分析,给出了试验梁的刚度退化方程及RPC主拉应力与疲劳寿命关系方程。