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《Construction and Building Materials》2007,21(6):1301-1310
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. 相似文献
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Mandizvidza Valentine Shambira Ghassan Nounu 《Construction and Building Materials》2000,14(8):425-432
This paper reports the results of an experimental study of the effect of time-dependent deformations (such as shrinkage and creep) of concrete repair materials on the ability of patch repairs to contribute to the structural function of reinforced concrete short columns. Prior to repair, strain measurements were taken from loaded columns with preformed cavities; cavity depths varied between columns. One polymeric and one polymer-modified concrete repair material were used for repair, all repairs being performed under zero load. After repair, the distribution of strain was measured from columns subjected to axial service load and from similar columns observed under zero load. Test results indicate that in the short term both the repair materials assist the repaired column to carry load, but in the long term the contribution of the polymer-modified material is reduced substantially while that of the polymeric material is sustained. It is observed that shrinkage of the repair material can induce bending in the repaired column and that this bending increases with patch repair cavity depth. Within the repaired zone, bending strain distributions were linear which would suggest that conventional methods of structural analysis are appropriate for such members. 相似文献
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《Construction and Building Materials》1999,13(4):195-212
The effectiveness of reinforced concrete repairs may be established in terms of their ability to restore the structural integrity of the reinforced concrete element and to protect the reinforcement from severe weathering conditions. Therefore, 18 large scale reinforced concrete beams were cast and subject to an accelerated corrosion mechanism in a chloride environment. The beams were repaired using two different materials for comparison purposes, namely an OPC mortar and a free flowing micro-concrete. Twelve beams were tested just after the repair material has cured, and the remaining beams were subjected to an aggressive weathering cycle for 6 months after which structural and electrochemical testing were conducted. This paper presents the results of both structural load testing of all beams, and physical and electrochemical performance of repaired beams before and during the accelerated weathering. The results of structural testing showed that in short-term situation both materials behaved very similar to each other and were able to restore 60–70% of the beams’ capacity. But in long-term situation the OPC mortar beams has deteriorated badly showing extensive cracking, while the free flowing micro concrete beams have shown very little cracking. The former restored only 40–50% of the capacity while the latter restored approximately 90%. The electrochemical monitoring data provided a useful comparison of two repair systems in terms of inhibitive influence of repairs on steel reinforcement and electrochemical interactions between the repaired and unrepaired areas. The protection afforded to the corroded rebars and subsequent reduction in corrosion rate was more significant with free flowing micro-concrete repair material than with OPC mortar. Incipient anodes were formed at the repair/concrete interfaces soon after the repair. Under accelerated weathering conditions, free flowing micro-concrete has been found to offer better resistance to chloride ingress from an external source than OPC mortar. A significant increase in corrosion rate and concrete surface weathering was observed in the climatic chamber, hence suggesting that a long term performance of a repair material can be assessed in a short time scale under these conditions. 相似文献
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《Construction and Building Materials》2007,21(5):937-951
This paper presents the results of experimental investigation undertaken for evaluating the cyclic response of concrete members which have already experienced structural damage and total loss of load resistance due to splitting bond failure of the tensile reinforcement, and then repaired for upgrading their bond strength and flexural capacity. The original (intact) specimens consisted of beams reinforced with identical top and bottom spliced reinforcement and subjected to inelastic cyclic load reversals until total bond degradation and complete loss of flexural strength. The repair procedure consisted of removing the deteriorated concrete within the damaged splice zone, adding concrete confinement and casting new concrete. Three types of concrete confinement were investigated, namely, internal confinement by steel ties or wire mesh reinforcement, and external confinement by FRP laminates. It was found that repairing the bond-damaged zone through concrete confinement leads to substantial regain of flexural stiffness and strength up to or exceeding those for the original specimens, reduces the structural damage, and results in considerable improvement of the energy absorption and dissipation capacity under cyclic loading. The experimental results were discussed, and comparison between the experimental data and analytical predictions is undertaken. 相似文献
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光纤Bragg光栅传感器在钢筋混凝土梁静荷载试验中的研究 总被引:2,自引:0,他引:2
光纤Bragg光栅的发展使传感器自标定 ,不受光波的波动影响 ,且于光源和连接损耗无关 ,而这些因素却一直困扰着其他类型的光纤传感器。将光纤Bragg光栅和传统电阻应变片分别贴于H15 4和H15 5梁的混凝土表面 ,以及H15 6和H15 8梁的钢筋表面 ,以分别检测钢筋的拉应变和混凝土的压应变。当钢筋混凝土梁受到千斤顶的加载时 ,其应变可由上述传感器检测得到。光纤Bragg光栅传感器的波长偏移提供了一种绝对测量 ,可避免对建筑结构的不间断检测 ,而代之以需要之时的周期性检测 相似文献
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按换算截面法推导了FRP片材加固混凝土梁的短期与长期挠曲变形计算公式,在此基础上编制了相应的分析计算程序,该分析方法能较准确预测开裂混凝土梁的长期挠曲变形。制作了10根钢筋混凝土梁,其中6根为普通钢筋混凝土梁,另外4根为CFRP片材加固梁,并对试件的短期与长期受力性能进行了试验观测,持续荷载作用下对试件进行了近700d的收缩徐变试验。运用本文计算方法预测了试件的长期挠曲变形,理论计算值与本文试验结果吻合较好。研究表明:碳纤维片材对混凝土梁的长期挠曲变形影响很小,但碳纤维片材能有效地控制持续荷载作用下裂缝的进一步开展。研究结果可为CFRP加固混凝土结构工程设计与理论分析提供参考。 相似文献
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《Construction and Building Materials》2007,21(4):789-798
Carbon fibre reinforced polymer (FRP) laminates are increasingly being used to strengthen reinforced concrete beams. Monitoring the integrity of the adhesive bond between the laminate and the concrete is important to establishing the long-term reliability of this technique. This paper discusses the development of a strain-based index in which the loss of strain compatibility can be used to identify regions where debonding has occurred. Theoretical and experimental work was conducted and the laminate tensile strain profiles were shown to be sensitive to the presence of induced debonded zones. The method has potential for broad implementation in many field monitoring applications. 相似文献
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电气光纤光栅测温火灾预警技术 总被引:1,自引:0,他引:1
分析了引发电气火灾的主要原因,针对火灾原因探讨了监测火灾预警的主要方法及存在的不足,提出了光纤光栅测温火灾预警技术的原理、工作特点及设备结构,并就其技术优势及应用作了相应探讨。 相似文献
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Detecting deformations in uncompacted strata by fiber Bragg grating sensors incorporated into GFRP 总被引:2,自引:0,他引:2
Jing Chai Jin-xuan LiuBiao Qiu Yi Li Lei ZhuShi-ming Wei Zhen-ping WangGuang-wen Zhang Jian-hua Yang 《Tunnelling and Underground Space Technology incorporating Trenchless Technology Research》2011,26(1):92-99
Coalfields based in east China, such as Huaibei, Datun, Xuzhou, Yanzhou, Yongxia and Huainan, have suffered paroxysmal shaft lining fracture and repeated deformation after repair in the last three decades. This phenomenon has required the development of fractured shaft lining repairing technology and a method for detecting rock strata settlement. It is proposed in this paper that, with the method of fiber Bragg grating sensor incorporated into GFRP, a sensing network of fiber Bragg grating wavelength division multiplexing (WDM)/spatial division multiplexing (SDM) mixing array composed of 18 fiber gratings is formed, and it is used for monitoring the settlement of uncompacted hydrous strata. It is the first time that the fiber Bragg grating sensing system is embedded into the 180-m deep uncompacted strata, and the field experiments are conducted at No. 3 Jingning Coal Mine. The layout of optical sensors, the fiber Bragg grating detecting system, the drilling of the borehole and the embedding method of fiber Bragg grating sensors are introduced. The monitoring results of fiber Bragg grating sensors are compared with groundwater level monitoring results. Engineering practice shows that the fiber Bragg grating sensors are working normally and they can be used to detect strain safely and stably. 相似文献
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《Construction and Building Materials》2000,14(4):189-197
The future of the concrete repair industry appears to be promising and bright, judging from the projections based on current trends in repair, rehabilitation, restoration and strengthening of existing infrastructure. However, this optimism must be tempered in light of the need to change the image of the industry as one that is often self-serving — the industry that is repairing the repairs. Due to the increasing public concern with durability of concrete structures in general, and repaired concrete structures in particular, the subject of steel corrosion and corrosion protection in repaired concrete structures is discussed with reference to the deficiencies in our knowledge of corrosion and corrosion protection in concrete repair, methods of testing, and in the science of repair durability. 相似文献
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混凝土裂缝会影响构件的耐久性,严重的裂缝还会影响结构的承载能力,因此,多数情况下需对混凝土裂缝进行修复处理。裂缝修复加固综合法是采用玄武岩纤维水泥砂浆和灌浆法修补混凝土裂缝。同时在梁底粘贴玄武岩纤维布提高构件抗弯承载力。试验表明,该综合修复技术既提高了构件的抗裂度和刚度,增强二次抗开裂能力,又有效提高受弯构件的抗弯承载力,达到综合修复的效果,经济效益优于目前常用修复技术。 相似文献
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光纤光栅应变传感器在测量过程中存在温度和应变交叉影响的问题,且温度对应力测量结果影响较大。为获得精确的应力测量结果,必须大幅度减少或消除温度的影响。目前参考光栅法或温度测量系数修正法,难获得理想的结果。文中提出以截面对称的悬臂梁结构作为敏感元件,利用其上下表面拉压异号等应变和温度变化同应变的原理,通过在悬臂梁上下表面对称粘贴两根光纤光栅,利用结果差来消除温度影响,并提高测量灵敏度。文中对此种温度自补偿新型光纤光栅应变传感器的传感性能进行了研究,并将此类传感器安装在拉索的锚具上进行索力测量。研究结果表明:研制的光纤光栅应变传感器,能大幅度降低温度的影响,达到温度自补偿的目的;将此类传感器用于索力测量,具有较高的精度及灵敏度,能满足工程应用的实际需要。 相似文献