碳纤维在混凝土结构加固中的原理与施工技术

碳纤维补强加固混凝土结构方法是近年来在国内外快速发展的一种结构补强加固新方法,由于碳纤维具有优良的物理力学性能,良好的粘结性、耐久性、自重轻、施工方便、快捷等优点,因而利用碳纤维加固混凝土构件,能有效地提高结构构件的承载能力、耐久性,由此达到对建筑物进行加固、补强的目的。文章以一个小型改造工程应用为例介绍了碳纤维在混凝土结构加固工程中的技术原理与施工技术。     

碳纤维增强加固混凝土技术

在碳纤维加固混凝土结构技术试验研究工作的基础上,对碳纤维增强加固混凝土技术进行了简要介绍。     

混凝土结构加固设计分析

文章针对混凝土结构加固的受力特征进行了详细分析,并提出了几种结构加固方案.提高结构加固设计承载力以及增强结构延性和整体性能,文章对结构工程加固具有实际意义.     

某种分槽混凝土基础结构检测与加固

通过对某种分槽混凝土基础的结构检测,认识到氢氧化铝制备工业种分槽内浆液荷载增大和物料对结构的腐蚀致使种分槽混凝土基础结构存在安全隐患。通过对该种分槽混凝土结构的检测与结构计算分析,针对安全隐患提出了相应的加固治理方案,从而解决了种分槽基础混凝土结构的安全隐患,工程实践结果表明加固维修效果良好。     

某办公楼结构加固与耐久性处理

结构因耐久性不足而造成的危害尚未被人们完全认识，混凝土结构也需要进行积极防护的观念还没被人们所接受．本文通过某办公楼的结构加固与耐久性处理，进一步说明结构耐久性的重要性，并介绍了钢构套加固法与喷射混凝土加固法．     

旧办公楼抗震鉴定与加固

介绍了某办公楼在加固前所进行的结构安全性检测情况,并根据监测结果作出鉴定结论,对不满足结构安全要求的墙体采用双面配筋混凝土加固,砖柱外包钢筋混凝土加固,以供类似工程参考。     

碳纤维布在宿舍楼梁、板裂缝封闭补强处理中的应用

结合高线宿舍楼维修改造情况，阐述选用碳纤维布加固补强的设计方案、施工工艺以及注意事项。说明碳纤维布加固修复混凝土结构技术适合钢筋混凝土的加固修补，且施工质量易于保证。     

碳纤维加固技术在铁路桥梁加固补强中的应用

利用碳纤维片高强和可粘贴的性能,把碳纤维片用环氧树脂粘贴在被补强的混凝土结构表面,有效封闭了混凝土裂缝,并与原混凝土结构形成一体共同承受荷载,使混凝土结构得到了有效的加固补强.     

广重集团三机车间改造加固实例

通过查明混凝土结构和基础的危害程度,将栈桥结构和基础缺陷分为一般缺陷、较严重缺陷和严重缺陷,并采取相应的处理对策和多种技术措施,使结构整体功能达到设计要求和延长使用寿命的目的,经过施工方案优化后,采用树根桩加固旧基础;用混凝土套子法加固旧柱。并指出施工中应注意事项。     

某工业构筑物混凝土基座腐蚀损伤检测

工业构筑物混凝土基座由于介质的不断侵蚀,造成了混凝土构件腐蚀损伤。需对此类混凝土结构进行检测,确定其腐蚀损伤程度,为后续隐患治理提供技术依据。这也是加固维修前的必要工作。总结了工业构筑物混凝土结构腐蚀损伤检测内容、检测方法,对类似因工业介质侵蚀的混凝土结构工程的检测鉴定具有借鉴意义。     

Construction and Testing of an Innovative Concrete Bridge Deck Totally Reinforced with Glass FRP Bars: Val-Alain Bridge on Highway 20 East

The Val-Alain Bridge, located in the Municipality of Val-Alain on Highway 20 East, crosses over Henri River in Québec, Canada. The bridge is a slab-on-girder type with a skew angle of 20° over a single span of 49.89?m and a total width of 12.57?m. The bridge has four simply supported steel girders spaced at 3,145?mm. The deck slab is a 225-mm-thick concrete slab, with semi-integral abutments, continuous over the steel girders with an overhang of 1,570?mm on each side. The concrete deck slab and the bridge barriers were reinforced with glass fiber reinforced polymer (GFRP) reinforcing bars utilizing high-performance concrete. The Val-Alain Bridge is the Canada’s first concrete bridge deck totally reinforced with GFRP reinforcing bars. Using such nonmetallic reinforcement in combination with high-performance concrete leads to an expected service life of more than 75?years. The bridge is well instrumented with electrical resistance strain gauges and fiber-optic sensors at critical locations to record internal strain data. Also, the bridge was tested for service performance using calibrated truckloads. Design concepts, construction details, and results of the first series of live load field tests are presented.     

Reinforced Concrete T-Beams Strengthened in Shear with Fiber Reinforced Polymer Sheets

This research studies the interaction of concrete, steel stirrups, and external fiber reinforced polymer (FRP) sheets in carrying shear loads in reinforced concrete beams. A total of eight tests were conducted on four laboratory-controlled concrete T-beams. The beams were subjected to a four-point loading. Each end of each beam was tested separately. Three types of FRP, uniaxial glass fiber, uniaxial carbon fiber, and triaxial glass fiber, were applied externally to strengthen the web of the T-beams, while some ends were left without FRP. The test results show that FRP reinforcement increases the maximum shear strengths between 15.4 and 42.2% over beams with no FRP. The magnitude of the increased shear capacity is dependent not only on the type of FRP but also on the amount of internal shear reinforcement. The triaxial glass fiber reinforced beam exhibited more ductile failure than the other FRP reinforced beams. This paper also presents a test model that is based on a rational mechanism and can predict the experimental results with excellent accuracy.     

Experimental Investigation on Seismic Retrofitting of Square RC Columns by Carbon FRP Sheet Confinement Combined with Transverse Short Glass FRP Bars in Bored Holes

Jacketing is less effective to large square/rectangular RC columns due to the inability of the rectangular-shaped jacket in restraining the dilation of concrete in the middle of a straight side. A new retrofit method is proposed in this work by fiber reinforcing the surface concrete in the middle of a straight side. Fiber reinforcing is achieved by inserting small fiber-reinforced polymer (FRP) bars into the concrete in the plastic hinge zone. The inserted FRP bars act as horizontal reinforcement to increase the ductility of the concrete in a similar way as that in normal fiber-reinforced concrete. When this fiber reinforcing technique is combined with the conventional jacketing, the concrete in all parts of a cross section may be effectively confined. In this work, experimental tests were undertaken to investigate the effectiveness of this new retrofit technique. Six half-scaled columns were tested and the test results demonstrated the effectiveness of the method.     

Numerical Cracking and Debonding Analysis of RC Beams Reinforced with FRP Sheet

Bonding a fiber reinforced polymer (FRP) sheet to the tension-side surface of reinforced concrete (RC) structures is often performed to upgrade the flexural capacity and stiffness. Except for upper concrete crushing, FRP sheet reinforcing RC structure may fail in sheet rupture, sheet peeloff failure due to opening of a critical diagonal crack, or concrete cover delamination failure from the sheet end. Accompanying the occurrence of these failure modes, reinforcing effects of the FRP sheet will be lost and load-carrying capacity of the RC structures will be decreased suddenly. This study is devoted to developing a numerical analysis method by using a three-dimensional elasto-plastic finite element method to simulate the load-carrying capacity of RC beams failed in the FRP sheet peeloff mode. Here, the discrete crack approach was employed to consider geometrical discontinuities such as opening of cracks, slipping of rebar, and debonding of the FRP sheet. Comparisons between analytical and experimental results confirm that the proposed numerical analysis method is appropriate for estimating the load-carrying capacity and failure behavior of RC beams flexurally reinforced with a FRP sheet.     

SBC-300型碳纤维布在加固钢筋混凝土梁设计中的应用

结合工程实例介绍SBC-300型碳纤维布加固钢筋混凝土梁设计和施工。实践证明该工程使用效果良好。该项新技术具有施工简便，安全可靠，耐久性好，不影响原结构外观等诸多优点。     

Punching Shear Behavior of Fiber Reinforced Polymers Reinforced Concrete Flat Slabs: Experimental Study

This paper presents the results of a two-phase experimental program investigating the punching shear behavior of fiber reinforced polymer reinforced concrete (FRP RC) flat slabs with and without carbon fiber reinforced polymer (CFRP) shear reinforcement. In the first phase, problems of bond slip and crack localization were identified. Decreasing the flexural bar spacing in the second phase successfully eliminated those problems and resulted in punching shear failure of the slabs. However, CFRP shear reinforcement was found to be inefficient in enhancing significantly the slab capacity due to its brittleness. A model, which accurately predicts the punching shear capacity of FRP RC slabs without shear reinforcement, is proposed and verified. For slabs with FRP shear reinforcement, it is proposed that the concrete shear resistance is reduced, but a strain limit of 0.0045 is recommended as maximum strain for the reinforcement. Comparisons of the slab capacities with ACI 318-95, ACI 440-98, and BS 8110 punching shear code equations, modified to incorporate FRP reinforcement, show either overestimated or conservative results.     

Fatigue Behavior of RC Beams Strengthened with GFRP Sheets

The objective of the presented study is to examine the effects of glass fiber reinforced polymer (GFRP) composite rehabilitation systems on the fatigue performance of reinforced concrete beams. Experiments were conducted on beams with and without GFRP composite sheets on their tensile surfaces. The specimens were 152 × 152 × 1,321 mm reinforced concrete beams with enough transverse reinforcement to avoid shear failure. The results of this study indicate that the fatigue life of reinforced concrete beams with the given geometry, subjected to the same cycling load, can be significantly extended through the use of externally bonded GFRP composite sheets. An interesting finding is that, although the fiber strengthening system increases the fatigue life of the beams, the failure mechanism, fatigue of the steel reinforcement, remains the same in both strengthened and nonstrengthened beams. Thus, it is possible to predict the fatigue life of a cyclically loaded beam using existing fatigue models.     

Development of FRP Reinforcement Guidelines for Prestressed Concrete Structures

Several national programs define the testing protocols and design guidelines for fiber reinforced polymer (FRP) reinforcement in concrete structures. This paper offers a review of these documents, comparing the materials testing and design philosophies for FRP reinforcement of different working groups. The work references Canadian, European, and Japanese efforts to codify these materials and assess the relative merits of each approach. The emphasis is on prestressing applications since the demands for sustained load capacity and full bond are more severe than for reinforced concrete.     

Concrete Beams Strengthened with Externally Bonded FRP Plates

The structural behavior of reinforced concrete beams strengthened with adhesively bonded fiber-reinforced plastics (FRP) is presented. The experimental work included flexural testing of 2.3-m-long concrete beams with bonded external reinforcements. The test variables included the amount of conventional (internal) reinforcement and also the type and amount of external reinforcement. For comparison, some of the beams were strengthened with bonded steel plates. Theoretical analyses included 2D nonlinear finite-element modeling incorporating a “damage” material model for concrete. In general there were reasonably good correlations between the experimental results and nonlinear finite-element models. It is suggested that the detachment of bonded external plates from the concrete, at ultimate loads, is governed by a limiting principal stress value at the concrete∕external plate interface.