内嵌CFRP板条加固RC梁抗剪承载力分析

分别对未加固和内嵌CFRP加固的钢筋混凝土梁建立了有限元模型,应用ANSYS软件进行非线性有限元分析,研究梁挠度和承载力,并与试验结果进行了比较,分析比较模拟结果和试验结果表明,所采用的有限元模型的合理性和有限元分析方法的正确性及CFRP加固钢筋混凝土梁可以显著提高其抗剪承载力。     

CFRP加固混凝土柱受剪承载力计算方法的分析

列举了国内外有关设计标准、指南和文献中的 7种CFRP布加固钢筋混凝土柱受剪承载力的计算方法 ,对国内外 3 3根柱的试验结果进行了验算 ,分析了各建议公式计算结果的可靠性和CFRP布对受剪的贡献 ,在此基础上提出了实用计算建议 ,供编制有关设计规范和工程设计参考。     

CFRP嵌入式加固RC柱的抗震性能研究

对于方形柱采用嵌入式加固时,在方形柱的两面开设槽口,在槽内放入CFRP板条。研究CFRP板条间距和轴压比对抗震能力的影响。采用有限元模拟RC柱在水平往复位移作用下受力过程,比较嵌入式加固柱与未进行加固柱的分析结果,NSM加固柱具有更高的抗剪承载力、更好的延性以和耗能能力。CFRP板条间距越小,轴压比越大,加固柱的抗震承载力越高,延性越好。     

碳纤维布加固钢筋混凝土短柱的抗剪承载力分析

对碳纤维布加固钢筋混凝土短柱进行了试验研究,结果表明,碳纤维布加固钢筋混凝土短柱能有效提高短柱的抗剪性能.本文基于试验结果分析和理论分析,提出了碳纤维布加固钢筋混凝土短柱的斜截面抗剪承载力的计算公式,可供工程设计和进一步研究参考.     

碳纤维布加固混凝土梁的抗剪承载力分析

本文根据碳纤维布加固混凝土克建的特点，对碳纤维布加固后混凝土梁的破坏形态做了分析，并对其抗剪承载能力做了讨论。     

碳纤维布加固钢筋混凝土短柱受剪承载力灰色关联分析计算

试验研究结果表明，影响碳纤维布加固钢筋混凝土短柱的斜截面受剪承载力主要因素有截面尺寸、混凝土强度等级、纵筋配筋率、配箍率、剪跨比及碳纤维配箍量等。为了经济有效地计算碳纤维布加固钢筋混凝土短柱的斜截面受剪承载力，应用灰色系统理论，对碳纤维布加固钢筋混凝土短柱的斜截面受剪承载力及其关联因子进行灰色关联分析，找出影响斜截面受剪承载力的主要因素。在此基础上，提出反映碳纤维布加固钢筋混凝土短柱受力特征的斜截面受剪承载力计算公式。     

CFRP加固RC混凝土梁抗弯设计方法

针对CFRP加固钢筋混凝土结构的受力特征，分析了CFRP加固钢筋混凝土梁的两种破坏形态，并给出了判断CFRP加固钢筋混凝土梁破坏形态的判别式，进一步推导出每一种破坏形态的理论计算公式。     

外包碳纤维布加固梁抗剪性能的试验研究

本文介绍了外包碳纤维布(CFRP)加固钢筋混凝土梁抗剪承载力试验的初步研究结果.试验中采用多种不同的碳纤维加固方式.试验研究表明,使用碳纤维布加固钢筋混凝土梁可以较普通钢筋混凝土梁获得更高的抗剪承载力和刚度.试验同时表明,加固效果取决于多种因素剪跨比,锚固长度,碳纤维布厚度及外包碳纤维布方案.     

CFRP加固钢筋混凝土梁二次受力抗剪试验研究

通过4个不同持续荷载下的CFRP加固梁抗剪试验,其中1个对比梁,3个不同荷载下的加固梁.试验结果表明,加固梁的极限抗剪承载力得到了提高,裂缝宽度和跨中挠度有所减小.发现现有的抗剪承载力计算公式远大于试验值,这是不安全的,进而提出了考虑二次受力的抗剪承载力计算公式,和试验结果吻合良好,具有一定的参考价值.     

CFRP外贴加固混凝土梁斜截面力学性能及影响因素的试验研究

通过8根碳纤维布加固混凝土粱的抗剪试验,研究了碳纤维布加固方式、加同量、条带间距及粘贴层数对混凝土梁抗剪加固效果的影响.试验结果表明:外贴CFRP条带能有效提高试件的抗剪承载力,其破坏模式主要为CFRP布黏结失效破坏.承载力提高程度与加固方式、加固量、条带间距及枯贴层数密切相关.在受剪过程中,CFRP材料在混凝土梁裂缝发生之后开始发挥作用,而且CFRP条带的应变在斜截面上的分布不均匀.     

碳纤维片材加固混凝土梁中粘结界面应力的有限元分析

为摸清碳纤维片材加固混凝土梁中粘接界面上的应力分布，本文利用ANSYS商业软件进行了有限元分析。重点研究了有限元计算模型、碳纤维片材层数以及U形箍对粘接界面应力的影响。研究结果表明，有限元计算模型、碳纤维片材层数对粘接界面端部的应力峰值有影响，U形箍会改变粘接界面上的应力分布。     

侧立面嵌贴碳纤维增强塑料板条加固混凝土梁受剪承载力研究

为研究加固钢筋混凝土梁的受剪承载力,按照沿梁轴向非对称布置箍筋的方式浇筑13根钢筋混凝土梁试件,在箍筋布置较少侧混凝土梁侧立面保护层上嵌入或外贴碳纤维增强塑料板条对混凝土梁进行受剪切补强。对其进行弯曲试验,研究内嵌碳纤维增强塑料板条补强混凝土梁的破坏形态、承载力等情况,并与相应位置外贴等量碳纤维增强塑料板条的混凝土梁进行比较,分析内嵌或外贴在混凝土梁上的碳纤维增强塑料板条应变变化情况及补强混凝土梁受剪承载力影响因素和受剪承载力计算方法。研究表明,与对比梁相比,内嵌碳纤维增强塑料板条补强混凝土梁受剪承载力提高18.8%~45.8%,外贴碳纤维增强塑料板条补强混凝土梁受剪承载力提高12.5%~13.3%,提出的承载力计算式计算结果与试验值吻合较好。     

外贴预应力CFRP片材加固RC梁施工关键问题分析

体外粘贴预应力CFRP(Carbon Fiber Reinforced Polymer以下简称CFRP)加固钢筋混凝土(RC)梁,施工技术水平对加固效果起到至关重要的作用,因此,合理地控制好施工过程具有重要意义。本文针对施工过程中关键问题的已有研究成果进行了总结和理论分析,为今后的设计和应用提供参考     

Experimental study on seismic strengthening of RC columns with wrapped CFRP sheets

Eight specimens, including two strengthened after being loaded to yield level to imitate strengthening with some damage and one strengthened under a sustained axial load to imitate strengthening under service condition, were tested under constant axial load and lateral cyclic load to investigate seismic performance of RC columns strengthened with carbon fiber reinforced polymer sheets (CFRP sheets). The ductility enhancement with the confinement of CFRP sheets was studied by the strain development and distribution in the CFRP sheets. Based on the experimental results, a confinement factor of CFRP and an equivalent transversal reinforcement index were suggested. Thus, the seismic design method of the current Chinese seismic design code for RC columns can be directly used in determining the amount of CFRP required for seismic strengthening.     

Fatigue-loading effect on RC beams strengthened with externally bonded FRP

External bonding of fiber-reinforced polymers (FRP) on concrete beams is particularly attractive for the strengthening of civil engineering structures in order to increase their strength and stiffness. Principles for design of such strengthening methods are now established and many guidelines exist. However, fatigue design procedure is still an ongoing research topic.This paper focuses on the damage behavior of FRP-strengthened reinforced concrete (RC) structures subjected to fatigue loading.In order to design bonded reinforcements, an iterative computational method based on section equilibrium and material properties (concrete, steel, adhesive and composite) has been previously developed by authors [1], [2], [3]. In the present study, this method is extended to describe the fatigue behavior of RC beams.A specific modeling coupled with an experimental investigation on large-scale beams made it possible to compare the theoretical and experimental fatigue behaviors of RC beams with and without composite reinforcements. The model is developed and calibrated using data of the literature or recorded during experiments specifically carried out for this study. Results showed that the beam deflection and the strain in each material could be calculated with a sufficient accuracy, so that the fatigue behavior of the FRP-strengthened beams was correctly estimated by the model.     

Effect of bond enhancement using carbon nanotubes on flexural behavior of RC beams strengthened with externally bonded CFRP sheets

This paper studied the effect of incorporation of carbon nanotubes (CNTs) in carbon fiber reinforced polymer (CFRP) on strengthening of reinforced concrete (RC) beams. The RC beams were prepared, strengthened in flexure by externally bonded CFRP or CNTs-modified CFRP sheets, and tested under four-point loading. The experimental results showed the ability of the CNTs to delay the initiation of the cracks and to enhance the flexural capacity of the beams strengthened with CFRP. A nonlinear finite element (FE) model was built, validated, and used to study the effect of various parameters on the strengthening efficiency of CNTs-modified CFRP. The studied parameters included concrete strength, flexural reinforcement ratio, and CFRP sheet configuration. The numerical results showed that utilization of CNTs in CFRP production improved the flexural capacity of the strengthened beams for U-shape and underside-strip configurations. The enhancement was more pronounced in the case of U-shape than in the case of use of sheet strip covers on the underside of the beam. In case of using underside-strip, the longer or the wider the sheet, the higher was the flexural capacity of the beams. The flexural enhancement of RC beams by strengthening with CNTs-modified CFRP decreased with increasing the rebar diameter and was not affected by concrete strength.     

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。     

碳纤维增强复合网格-聚合物水泥砂浆加固RC梁抗剪性能试验研究

为研究碳纤维增强复合(CFRP)网格和聚合物水泥砂浆(PCM)复合加固工字形截面钢筋混凝土(RC)梁的抗剪性能,对3个试件进行抗剪性能试验和有限元模拟,分析了CFRP网格-PCM加固RC梁的抗剪破坏机理,研究了不同加固方式对试件抗剪性能的影响。研究结果表明:采用CFRP网格-PCM对RC梁进行抗剪加固可有效抑制斜裂缝的发展,能够较大幅度提高RC梁的抗剪承载力;相比仅腹部加固的试件,腹部和腋部都加固的试件的二次刚度、极限荷载均有所提高,且CFRP网格变形减小,与混凝土界面的黏结能力增强;在有限元分析中,采用混凝土的CDP模型和Spring2弹簧单元来预测CFRP网格加固混凝土的抗剪承载力是可行的;建立了基于杆状材料有效应变的抗剪计算方法,该方法可有效预测加固RC梁的抗剪承载力,为结构加固设计提供参考。     

外贴碳纤维布在混凝土结构加固中的应用

阐述了碳纤维布的性能及该材料在混凝土结构加固技术中的应用,结合工程实践总结了加固施工工艺和技术要点,并进行了检验及验收,证实了碳纤维布加固技术的可行性。