内嵌CFRP筋/片加固木梁受弯性能试验研究

为研究内嵌CFRP筋/片加固木梁的受弯性能,制作5根底面中心内嵌CFRP筋加固试件,3根侧面内嵌CFRP筋加固试件,6根底面中心内嵌CFRP片加固试件以及3根未加固的对比试件,对其进行三分点静载试验。试验参数包括：CFRP筋/片,内嵌位置（底面或侧面）,CFRP筋/片数量（1根或2根）、是否采用附加锚固措施（U形铁钉或CFRP布U形箍）、底面是否粘贴CFRP布等。研究表明,内嵌CFRP筋/片加固试件的受弯承载力较未加固试件明显提高,提高幅度为14%~85%,平均提高39%;破坏位移亦平均提高32%。内嵌CFRP筋加固试件的初始弯曲刚度均大于对比试件,而内嵌CFRP片加固试件由于底面开槽面积较大其初始弯曲刚度未见提高。内嵌CFRP筋加固试件的跨中截面应变随荷载增加仍基本符合平截面假定,而内嵌CFRP片加固木梁的跨中截面应变变化与平截面假定存在一定差距。增加内嵌CFRP筋/片的数量及端部采用U形铁钉锚固措施对提高加固木梁承载力的作用不明显;而在加固木梁底面粘贴一层CFRP布可显著提高其加固效果。     

砖的强度富余系数及其对砌体结构可靠度的影响

在统计分析大量砖强度试验数据的基础上,探讨了砖强度等级评定方法和砖的强度富余系数对砌体结构静力计算的影响,可供砖材试验人员和结构工程师参考。     

NSM加固技术在RC梁抗弯加固方面的发展现状

简单介绍了表面嵌贴FRP加固技术的发展,并介绍了该技术在钢筋混凝土梁抗弯加固方面的破坏形式的试验研究与承载力计算的理论,并且提出了一些展望。     

Evaluation of the transfer length of prestressed near surface mounted CFRP rods in concrete

The transfer length of a prestressed near surface mounted (NSM) fiber reinforced polymer (FRP) rod is the distance over which the rod must be bonded to the epoxy to develop the prestressing force in the rod. The transfer length is intended to provide bond integrity for the strengthened concrete member. This paper presents experimental results and an empirical equation to estimate the transfer length of prestressed NSM Carbon FRP (CFRP) rod in concrete beams. Twenty-two reinforced concrete specimens were strengthened with NSM CFRP rods. Two types of CFRP rods were used: spirally wound and sand blasted rods. Four prestressing levels were used: 40%, 45%, 50% and 60% of the tensile strength of the CFRP rod. The strain behavior in the CFRP rod was monitored by gauges mounted on the CFRP rod along the length of the beam. The test results showed that the transfer length of the prestressed NSM CFRP rod was about 35 times the diameter of the CFRP rod. The maximum bond stress of the CFRP rod in epoxy was found to range from 11 to 16 MPa for the sand blasted rods and from 12 to 23 MPa for the spirally wound rods. An empirical expression based on curve fitting of the measured data was proposed to predict the prestressing stress in the CFRP rod along the length of the beam.     

浅谈碳纤维加固应用技术

对碳纤维加固技术进行了介绍,从材料、特点和适用范围对碳纤维加固技术进行了说明,分析了碳纤维补强加固的原理,提出了碳纤维加固技术的工艺流程及操作要求,指出了碳纤维加固技术具有较大的经济效益,应用前景光明。     

某工程碳纤维布结构加固及其加固质量的检查与验收

结合工程实际,总结碳纤维布加固法的施工工艺及技术关键,并对其加固工程质量的检测与验收进行探讨与研究。     

碳纤维加固钢筋混凝土施工技术

阐述了采用碳纤维布加固的优点、材料特性及其构造做法,详细介绍了碳纤维布加固钢筋混凝土的施工工艺,指出该技术是一种经济、适用、新型的结构方法,且具有轻质高强、施工便捷、耐腐蚀性和耐久性强等优点,值得推广使用。     

碳纤维加固技术的应用实例

结合具体的工程实例，对碳纤维加固技术的优点作了分析，介绍了某旧楼改造的设计要求，详细阐述了碳纤维加固的施工工艺流程及施工要点，并提出一些可解决存在问题的方法。     

碳纤维材料在加固工程中的应用研究

作为一种新型加固材料,碳纤维材料（CFRP）具有高强,轻质,耐腐蚀等优点。本文介绍了国内外有关加固用CFRP的研究与应用的最新进展。     

内嵌筋材加固混凝土梁弯曲性能研究

探讨了内嵌碳纤维筋和内嵌螺旋肋钢丝加固混凝土构件对比试验研究,并分析了不同筋材,加固量对被加固构件抗弯性能的影响.结果表明:两种加固方法均能大幅度提高被加同构件的极限承载力,改善梁的裂缝开展情况,但内嵌碳纤维筋加固方法易于发生黏结破坏,螺旋肋钢丝的黏结效果较好,且在经济性上明显优于碳纤维材料,更利于在工程实际中推广应用...     

Environmental durability of a CFRP system for strengthening steel structures

Recently a high modulus CFRP system was developed to enhance the load carrying capacity and serviceability of steel bridges and structures. However, the environmental durability of the system has not yet been demonstrated. This paper presents the findings of a research program that was conducted to evaluate the environmental durability of the bond of the proposed CFRP strengthening system to steel surfaces. The program consisted of testing 44 steel-CFRP double-lap shear specimens. The specimens were exposed to severe environmental conditions for different durations, up to 6 months. Different methods to enhance the bond durability were studied including pre-treating the steel surface with a silane coupling agent, inserting a glass fiber layer within the adhesive and a combination of both methods of protection. The research findings indicate that the use of a silane coupling agent significantly enhanced the bond durability. While the presence of the glass fibers helped to enhance the initial bond strength of the system, it did not improve the durability of the bond. The use of both techniques enhanced both the overall bond strength and the environmental durability of the strengthening system.     

碳纤维复合材料在结构加固中的应用现状

对碳纤维布的优点和它在结构加固中的应用现状进行了总结，探讨了碳纤维加固的结构，指出了其中的主要形式存在的一些问题，为今后的发展方向提供了可以参考的建议。     

Damaged RC beams repaired by bonding of CFRP laminates

This paper summarizes the results of experimental studies on damaged reinforced concrete beams repaired by external bonding of carbon fiber reinforced polymer (CFRP) composite laminates to the tensile face of the beam. Two sets of beams were tested in this study: control beams (without CFRP laminates) and damaged and then repaired beams with different amounts of CFRP laminates by varying different parameters (damage degree, CFRP laminate width, concrete strength class). All beams were tested in four-point bending over a span of 1800 mm. The tests were carried out under displacement control. The most investigated parameter in this experimental study is damage degree (ratio between pre-cracked load and load capacity of control beam). Repairing damaged RC beams with externally bonded CFRP laminates were successful for different degrees of damage. The observed failure modes were peeling off and interfacial debonding. These failure modes depend only on the laminate width.The results indicate that the load capacity and the rigidity of repaired beams were significantly higher then those of control beam for all tested damage degrees. The authors remarked that for a load capacity improvement, reinforcement with a CFRP having about a half width of the beam is satisfactory. Finally, the contribution of CFRP laminates on the load capacity and rigidity of repaired RC beams is significant for any concrete strength class.     

Interfacial behavior of mechanically anchored FRP laminates for strengthening steel beams

This study investigates the response of FRP–steel anchored lap connections along with the associated interfacial behavior. The investigation is conducted experimentally and numerically. The experimental program includes testing of eighteen short specimens to explore the influence of sheared edge distance and rolled edge distance on the load carrying capacity and ductility of the assembly. In addition, six longer connections are tested to assess the effect of the spacing between bolts on the response. The findings suggest a sheared edge distance of about six to seven times the bolt hole's diameter. The effect of the rolled edge distance values considered in the study on the performance of the connections is found to be insignificant. A non-linear load–slip model is proposed to simulate the interfacial behavior of the assembly. A finite element study is conducted using an equivalent non-linear spring element to simulate the interfacial behavior based on the proposed load–slip model. The excellent match between displacement and strain responses measured experimentally and their numerical predictions validates the accuracy of the proposed load–slip model. The flexural behavior of two full-scale I-shaped steel beams is then investigated experimentally to explore the enhancement in the response of beams strengthened with mechanically anchored FRP laminates. Finally, a finite element model is utilized to predict the elasto-plastic response of the tested steel beams. The excellent agreement between the numerical predictions and experimental measurements provides another validation for the proposed load–slip model.     

混凝土梁碳纤维加固机理力法简析

根据碳纤维加固梁的构造、加固机理和材料性能，用力法求解链杆的内力，确定了加固梁各部分的受力关系，并提出要对反映受力关系的系数K作进一步的探讨。     

The problem of shear in RC beams strengthened with CFRP laminates

The effectiveness of externally bonded reinforcement of a strengthened Reinforced Concrete (RC) beam subjected to a shear-dominant loading regime is not well-established. The aim of this paper is to clarify the structural performance of RC beams without any internal shear reinforcement but strengthened with Carbon Fibre Reinforced Polymer (CFRP) laminates when the primary mode of failure of the un-strengthened beam is in shear. Four RC beams were specifically designed without and with an externally anchorage system, which was carefully detailed to enhance the benefits of the strengthening lamina and counteract the destructive effects of shear forces. All the four beams were identical in terms of their geometry, internal reinforcement and concrete strength but varied in their test loading regime to highlight the role of shear. All the beams were tested under four point bending and extensively instrumented to monitor strains, cracking, load capacity and failure modes. The structural response of the four beams is then critically analysed in terms of deformability, strength and failure processes under a shear loading regime. It is shown that with a carefully designed anchorage system, a predominantly brittle shear failure of a strengthened beam can be transformed to an almost ductile failure with well-defined enhancement of structural performance in terms of both deformation and strength. The results presented in this paper should enable engineers to totally avoid shear failure in strengthening beams with little or even no internal shear reinforcement.     

苯丙乳液水泥基胶结材料在碳纤维加固混凝土梁中的应用研究

目前的CFRP加固多使用环氧树脂作胶结材料,但是环氧树脂脆性大,耐久性较差。本文尝试使用苯丙乳液改性水泥浆体取代环氧树脂,用碳纤维布加固混凝土梁,测试其弯曲荷载-挠度曲线。结果表明：使用掺加苯丙乳液水泥浆体作为CFRP加固的胶结材料,与普通水泥浆体相比,当胶结材料中苯丙乳液的掺量为4％时,弯曲荷载基本相同,梁的挠度从0．3mm提高到3mm左右。     

GFRP片材约束柱极限承载力试验

对6个素混凝土柱、钢筋混凝土柱、GFRP片材约束混凝土柱轴心受压情况下的极限承载力进行了试验研究,就不同类型柱体的极限承载力进行了对比分析,并得出了相应的结论,可供相关技术人员参考。     

Tests on reinforced concrete beams strengthened in shear using near surface mounted CFRP and steel bars

This paper presents the experimental results obtained from testing four large scale reinforced concrete T-beams strengthened in shear using near surface mounted (NSM) carbon fiber reinforced polymer (CFRP) bars and conventional steel reinforcing bars. The experimental program studied the effects of the orientation of the NSM bars, their type and their anchorage into the flange concrete. The tests showed that the NSM bars were engaged in the resistance as soon as they were crossed by a crack. The strengthening increased the shear capacity by 37%-92%, reduced the width of the diagonal cracks and allowed the beams to develop significant flexural ductility. The results also showed that orienting the NSM bars at 45° and extending their anchorage into the flange concrete improved the efficiency of strengthening. The CFRP strengthened test regions achieved 7%-10% larger shear capacity than the steel strengthened test regions, and their behavior was relatively similar.     

CFRP加固钢筋混凝土结构的研究及应用现状

碳纤维增强聚合物(CFRP)材料具有轻质高强等优良性能,广泛应用于钢筋混凝土结构加固工程。介绍CFRP加固混凝土梁、板、柱以及抗震加固和抗疲劳加固的相关研究,以及CFRP加固钢筋混凝土结构的施工技术及国内外典型工程应用情况。