中英文 混合纤维增强塑料片的混凝土梁–柱联接部位的加固

混凝土结构中纤维增强复合材料的应用技术研究一、引言混凝土是建筑中普遍使用的材料，因其具有良好的压缩性能和耐久性而得到广泛应用。

但是，混凝土的受拉性能较差，易于开裂，降低了其使用寿命和安全性。

为了改善混凝土的受拉性能，纤维增强复合材料（Fiber Reinforced Polymer，FRP）被引入到混凝土结构中。

近年来，纤维增强混凝土（Fiber Reinforced Concrete，FRC）已经成为一种重要的新型复合材料，其具有高强度、高韧性、耐久性好等优点。

本文将详细介绍混凝土结构中纤维增强复合材料的应用技术研究。

二、FRC的分类FRC是一种由纤维和混凝土组成的复合材料。

根据纤维种类的不同，FRC可以分为以下几类：1. 钢纤维混凝土：钢纤维混凝土是将钢纤维掺入混凝土中，以提高混凝土的韧性和抗裂性能。

钢纤维可以是钢丝、钢棒、钢纱等形式，其直径一般为0.2~1.0mm，长度为25~60mm。

2. 碳纤维混凝土：碳纤维混凝土是将碳纤维掺入混凝土中，以提高混凝土的强度和刚度。

碳纤维具有高强度、高模量、低密度等优点，但其价格较高。

3. 玻璃纤维混凝土：玻璃纤维混凝土是将玻璃纤维掺入混凝土中，以提高混凝土的韧性和抗裂性能。

玻璃纤维具有良好的耐碱性和耐腐蚀性，但其强度较低。

4. 天然纤维混凝土：天然纤维混凝土是将天然纤维掺入混凝土中，以提高混凝土的韧性和抗裂性能。

常用的天然纤维有木材纤维、竹子纤维、麻类纤维等。

三、FRC的性能FRC的性能主要取决于所使用的纤维种类、纤维含量、纤维长度和混凝土配合比等因素。

下面介绍FRC的一些基本性能：1. 强度：FRC的强度主要取决于所使用的纤维种类和纤维含量。

一般来说，钢纤维混凝土的强度较高，碳纤维混凝土次之，玻璃纤维混凝土最低。

2. 韧性：FRC的韧性主要取决于纤维的长度和含量。

纤维长度越长，韧性越好。

纤维含量越高，韧性越好。

3. 耐久性：FRC的耐久性主要取决于纤维的耐久性和混凝土配合比。

使用加固纤维聚合物增强混凝土梁的延性作者：Nabil F. Grace, George Abel-Sayed, Wael F. Ragheb摘要：一种为加强结构延性的新型单轴柔软加强质地的聚合物(FRP)已在被研究，开发和生产(在结构测试的中心在劳伦斯技术大学)。

这种织物是两种碳纤维和一种玻璃纤维的混合物，而且经过设计它们在受拉屈服时应变值较低，从而体现出伪延性的性能。

通过对八根混凝土梁在弯曲荷载作用下的加固和检测对研制中的织物的效果和延性进行了研究。

用现在常用的单向碳纤维薄片、织物和板进行加固的相似梁也进行了检测，以便同用研制中的织物加固梁进行性能上的比较。

这种织物经过设计具有和加固梁中的钢筋同时屈服的潜力，从而和未加固梁一样，它也能得到屈服台阶。

相对于那些用现在常用的碳纤维加固体系进行加固的梁，这种研制中的织物加固的梁承受更高的屈服荷载，并且有更高的延性指标。

这种研制中的织物对加固机制体现出更大的贡献。

关键词：混凝土，延性，纤维加固，变形介绍外贴粘合纤维增强聚合物（FRP）片和条带近来已经被确定是一种对钢筋混凝土结构进行修复和加固的有效手段。

关于应用外贴粘合FRP板、薄片和织物对混凝土梁进行变形加固的钢筋混凝土梁的性能，一些试验研究调查已经进行过报告。

Saadatmanesh和Ehsani（1991）检测了应用玻璃纤维增强聚合物(GFRP)板进行变形加固的钢筋混凝土梁的性能。

Ritchie等人（1991）检测了应用GFRP，碳纤维增强聚合物（CFRP）和G/CFRP板进行变形加固的钢筋混凝土梁的性能。

Grace等人（1999）和Triantafillou（1992）研究了应用CFRP薄片进行变形加固的钢筋混凝土梁的性能。

Norris，Saadatmanesh和Ehsani（1997）研究了应用单向CFRP薄片和CFRP织物进行加固的混凝土梁的性能。

在所有的这些研究中，加固的梁比未加固的梁承受更高的极限荷载。

混凝土建筑主要的加固方法
混凝土建筑是现代建筑中最常见的形式之一。

它们通常是耐久、坚固的建筑，但在某些情况下，它们需要进行加固以确保其能够承受更大的重量或更严格的环境条件。

以下是混凝土建筑主要的加固方法：
1. 纤维增强混凝土 (FRC)
纤维增强混凝土是通过在混凝土中添加纤维来增加其强度和耐
久性的一种方法。

这些纤维通常是玻璃、钢或聚合物纤维。

FRC通常用于加固桥梁、隧道等结构。

2. 表面处理
表面处理可以通过密封、填充、修补、涂装等方式来增强混凝土的表面。

这可以帮助减少混凝土的吸水性、增加其耐久性和抵抗化学腐蚀的能力。

3. 碳纤维加固
碳纤维加固是通过在混凝土表面或内部使用碳纤维增强合成材
料 (CFRP) 来增加其强度和刚度的一种方法。

这种方法在加固混凝土柱、梁或板等结构时十分有效。

4. 预应力混凝土
预应力混凝土是一种通过在混凝土中预先应力的一种方法。

这种方法可以帮助加固混凝土结构并增加其承载能力。

总之，混凝土建筑主要的加固方法有纤维增强混凝土、表面处理、碳纤维加固和预应力混凝土。

这些方法可以帮助加固混凝土结构并增
强其强度、耐久性和承载能力。

《高等钢筋混凝土结构》结课论文纤维增强塑料混凝土结构的应用与发展The application and development of Fiber Reinforced Plastic in theConcrete structure摘要纤维增强塑料因其强度重量比及刚度质量比高、热膨胀系数低、各向异性、轻质、耐腐、无磁、有良好的抗疲劳性能及高耐久性等特点，可广泛应用于桥梁、岩土工程和建筑工程中。

本文介绍了FRP材料在新建结构、结构加固、桥梁中以及预应力FRP在混凝土结构中的研究和应用状况，并提出了结构用FRP在使用方面的一些问题和开发研究前景。

关键词：纤维增强塑料；复合材料；结构加固；使用现状；目录1 纤维增强塑料的概述 (3)1.1 纤维增强塑料的组成 (3)1.2 纤维增强塑料的特性 (4)2 结构用纤维增强塑料的研究现状 (5)2.1 纤维增强塑料在新建结构中的研究与应用 (5)2.2 纤维增强塑料在结构加固修复补强中的研究与应用 (6)3 结构用纤维增强塑料的问题和研究开发前景 (12)4 结语 (13)5 参考文献 (14)纤维增强塑料混凝土结构的应用与发展在钢筋混凝土的使用中，由于钢筋锈蚀常常造成结构耐久性差，不仅影响结构功能的正常发挥，还会严重降低结构的使用寿命，为此提出利用纤维增强塑料（英文名称Fiber Reinforced Plastic，简称FRP）代替钢筋和预应力钢筋来解决这一问题。

到目前为止，许多国家已进行了试验研究并应用到工程中，在日本已经产生最早的关于纤维增强塑料的建筑混凝土结构设计指南，在欧洲和美国等一些国家也正在编制过程中。

在这方面虽然我国起步比较晚，但也进行了大量的试验研究。

1 纤维增强塑料的概述1.1 纤维增强塑料的组成纤维增强塑料是由多股连续纤维通过基底材料进行胶合后，再经过特制的模具挤压和拨拉成型的。

其中纤维起加劲作用，主要有玻璃纤维、碳纤维、芳纶纤维等，基材主要起粘结和传递剪力作用，主要有聚醋树脂、环氧树脂、聚酞胺树脂等。

混凝土梁柱中纤维增强材料的应用技术规程一、前言混凝土结构是现代建筑中使用最广泛的结构形式之一。

混凝土结构由梁、柱、板、墙等组成，它们承受着建筑物自重和外部荷载。

传统的混凝土结构的强度和韧性都依赖于钢筋的加固，但是钢筋的使用增加了结构的成本和施工难度。

为了降低结构的成本和提高施工效率，纤维增强混凝土（Fiber Reinforced Concrete，简称FRC）被引入到混凝土结构中。

二、FRC的基本概念纤维增强混凝土是一种利用纤维增加混凝土韧性和抗裂性的混凝土，它是一种具有高强度和高韧性的复合材料。

FRC的基本成分是混凝土和纤维，纤维可以是钢纤维、玻璃纤维、聚合物纤维等。

纤维的加入可以增加混凝土的韧性和抗裂性，同时还能提高混凝土的抗冲击性、耐久性和抗震性能。

三、FRC的应用技术规程1.纤维的选择和加入量纤维的选择应根据结构的使用条件、荷载和环境等因素来确定。

一般来说，钢纤维的加入量为混凝土体积的0.5%~2.0%，玻璃纤维的加入量为混凝土体积的0.5%~1.0%，聚合物纤维的加入量为混凝土体积的0.2%~0.5%。

2.混凝土的配合比设计FRC的配合比设计应根据结构的使用条件、荷载和环境等因素来确定。

在设计配合比时，应考虑纤维的加入量、混凝土的强度要求以及混凝土的流动性等因素。

3.混凝土的搅拌与浇筑FRC的搅拌和浇筑应按照普通混凝土的要求进行。

在搅拌混凝土时，应注意控制混凝土的流动性，避免纤维集中在混凝土的一侧或某一部位。

在浇筑混凝土时，应注意控制浇筑速度，避免混凝土的浪涌和分层现象。

4.混凝土的养护FRC的养护应按照普通混凝土的要求进行。

在养护期间，应注意控制湿度和温度，避免混凝土龟裂和表面起砂。

5.施工质量检验FRC的施工质量检验应按照普通混凝土的要求进行。

检验内容包括混凝土的强度、韧性、抗裂性、抗冲击性、耐久性和抗震性能等。

四、FRC的应用案例1.钢纤维增强混凝土桥梁钢纤维增强混凝土桥梁是一种新型的桥梁结构形式，它具有高强度、高韧性、高耐久性和高抗震性能。

纤维复合材料加固钢筋混凝土柱的施工方法随着建筑技术的发展，纤维复合材料（FRP）成为加固钢筋混凝土柱的有效方法。

FRP加固是指在被加固结构表面层次增加FRP管或板材，通过FRP与结构表面间建立良好的键合，能够有效改善混凝土柱的抗拉能力，防止或减少钢筋锈蚀，延长柱的使用寿命。

以下是纤维复合材料加固钢筋混凝土柱的施工方法：1.先，清洁混凝土柱表面，清除尘埃，污垢，表面多孔性物质，以便确保FRP与混凝土柱之间有良好的键合。

2.后，在混凝土柱表面涂抹弹性胶水，使FRP更好地附着于表面，并对锚固点进行涂料加固，以保证它们能够有效起到锚固的作用。

3.下来，在表面层次增加FRP管或板材，使其与混凝土表面接触后，用胶粘剂将其固定在表面上。

4.后，将FRP管或板材用熔接设备加热，使它们更加牢固地锚在结构表面上。

FRP加固技术在工程项目中应用广泛，它可以提高混凝土柱表面强度，降低混凝土柱出现裂缝，腐蚀问题的可能性，从而延长混凝土柱的使用寿命。

不仅如此，FRP加固技术具有操作简便快捷的特点，相对于传统的加固补强方法，施工成本降低许多，而且具有自支撑性，不受地基质量的影响，可以把大量的材料和劳动力节省到最小，降低工程总体投资成本。

此外，FRP材料具有良好的耐腐蚀性能，可以有效抵抗各种强腐蚀液体，因此，FRP加固可以有效防止或减小钢筋锈蚀，从而提高结构的耐久性。

通过以上介绍，可以看出FRP加固技术在加固钢筋混凝土柱方面具有重要的作用，它不仅可以提高柱的强度和稳定性，而且施工简单，节约成本，可以抵抗各种强腐蚀液体，延长混凝土柱的使用寿命。

因此，FRP加固将是未来的发展重点，有助于加固钢筋混凝土柱，改善建筑物的安全性，确保结构的耐久性和可靠性，把工程建设及安全使用推向一个新的高度。

附录C 外文文献及翻译Strengthening of reinforced concrete beams using ultra high performance fibre reinforced concrete (UHPFRC) Highlights•Experimental investigation was conducted to determine mechanical properties and shrinkage of UHPFRC.•Numerical model was dev eloped for the simulation of UHPFRC.•The efficiency of UHPFRC layers and jackets for the strengthening of existing beams was assessed.•Superior performance was observed in terms of stiffness, yield and maximum strength, when three side UHPFRC jacket was used.AbstractIn this study the efficiency of the use of Ultra High Performance Fibre Reinforced Concrete (UHPFRC) for the strengthening of existing Reinforced Concrete (RC) beams has been investigated. Experimental work has been conducted to determine UHPFRC material properties. Dog-bone shaped specimens have been tested under direct tensile loading, and standard cubes have been tested in compression. These results have been used for the development of a numerical model using Finite Element Method. The reliability of the numerical model has been validated using further experimental results of UHPFRC layers tested under flexural loading. Further numerical study has been conducted on full-scale beams strengthened with UHPFRC layers and jackets, and these results were compared to respective results of beams strengthened with conventional RC layers and with combination of UHPFRC and steel reinforcing bars. Superior performance was observed for strengthened beams with UHPFRC three side jackets, and the efficiency of this technique was highlighted by comparisons with other strengthening techniques.Keywords•Ultra high performance fibre reinforced concrete;•Reinforced concrete beams;•Strengthening;•Layers;•Jackets1.IntroductionA novel technique used to improve the performance of existing structural elements is the application of additional Ultra High Performance Fibre Reinforced Concrete (UHPFRC) layers or jackets in connection to the existing elements. The efficiency of this technique has not been adequately studied, and there are not any published studies on the evaluation of this method with comparisons to other traditional strengthening methods such as the use of Reinforced Concrete (RC) layers and jackets.The technique of strengthening using additional RC layers and jackets is one of themost commonly used techniques in seismic areas. There are several published experimental and theoretical studies on beams and columns strengthened with conventional concrete [1], [2], [3], [4], [5], [6], [7], [8], [9], [10], [11], [12], [13], [14] and [15]. A crucial parameter in this technique, which can considerably affect the durability and the performance of the strengthened structures, is the concrete shrinkage strain of the additional layers/jackets. Additional stresses are induced in strengthened elements, and cracking of the new layer and/or de-bonding may occur [8], [9], [10], [11], [12], [13], [14] and [15]. The use of UHPFRC could potentially improve both durability and resistance due to its superior mechanical properties.This study is focused on the addition of UHPFRC layers or jackets to existing RC beams. UHPFRC is a novel material with superior strength and energy absorption. There are several published studies on UHPFRC and the mechanical properties of this material have been studied extensively [16], [17], [18], [19], [20] and [21]. The percentage of the steel fibres is one of the most crucial parameters affecting the flexural strength and the ductility of UHPFRC elements. According to published experimental studies [16] and [17], increment of the steel fibres amount, results to an increment of the flexural strength, while the ductility is reduced. The effect of fibres’ orientation and distribution in the mix was investigated by Kang and Kim [18]. According to this study [18], fibres’ orientation and distribution has negligible effect in the pre-cracking behaviour while in the post-cracking phase, this considerably affects the material properties. Experimental test methods appropriate for the evaluation of the mechanical properties of UHPFRC were proposed by Hassan et al.[19]. A detailed investigation on the assessment of the performance of UHPFRC was presented by Toledo et al. [20], and the development of the mechanical properties of UHPFRC with the time was extensively studied by Habel et al. [21]. The direct tensile behaviour of UHPFRC was examined by Kang et al. [16], and tri-linear tensile fracture model with softening phase was proposed via an inverse analysis. An inverse finite element analysis method was also proposed by Neocleous et al. [22] for deriving the tensile characteristics of Steel Fibre Reinforced Concrete (SFRC). The effect of fibre distribution on UHPFRC was highlighted in Ferrara et al. [23]. In this study the effect of different fibre orientations was examined. For this reason, slabs with the same size but different flowing direction were cast. From these slabs, beam specimens were cut with theiraxis parallel and perpendicular to the flow direction. From the results it was evident that the orientation of the fibres considerably affects the mechanical performance of fibre reinforced cementitious composites [23].The findings presented in the previous studies are mostly focused on the mechanical properties of UHPFRC, and there are other published studies on strengthening applications [24], [25], [26], [27], [28], [29], [30] and [31]. Farhat et al. [24] examined beams strengthened with UHPFRC strips. Epoxy adhesive was used for the bonding between UHPFRC and the initial beam. In this study [24], UHPFRC prevented shear failure of the beams and the failure load was increased up to 86%. Brühwiler and Denarie [25] and Brühwiler [26] studied the application of UHPFRC for the rehabilitation of crash barrier wall of highway bridge, bridge pier, andindustrial floors, and the efficiency of this method for cast in-situ and prefabrication, using standard equipment for concrete manufacturing, was highlighted. The application of UHPFRC for the repair and strengthening of beam-column joints was investigated by Beschi etal. [29] and remarkable bearing capacity increment was observed [29]. Combination of UHPFRC with reinforcing steel bars for the rehabilitation of existing concrete elements was examined by Habel et al. [27] and this technique was found to be quite promising, since the existing structures were efficiently strengthened and their resistance and their ultimate moment were considerably increased [27]. An analytical model for elements strengthened with combined UHPFRC and steel bars was proposed by Noshiravani and Brühwiler [28] together with a simplified formulation for the shear resistance of the composite members [28]. Magri et al. [30] investigated the combination of UHPFRC with Textile Reinforced Mortar (TRM) and increment of maximum load capacity and ductility of the examined specimens was observed [30].However, until now, there are not any published studies on three sides jacketing with UHPFRC, and there are not any direct comparisons of the use of UHPFRC layers or jackets with traditional strengthening techniques. The main aim of this paper is to investigate the effectiveness of the addition of UHPFRC layers or jackets to RC beams and to conduct a critical comparison of the effectiveness of this novel technique with traditional strengthening methods using RC layers. In this paper, a numerical investigation is presented first (Section 2) on initial, prior to strengthening, RC beams. Experimental work was conducted to determine the actual material characteristics in tension and compression and, using these data, a numerical model was developed for the simulation of UHPFRC. The accuracy of the model was further validated with flexural tests on UHPFRC layers (Section 3). An extensive numerical investigation was conducted on beams strengthened with layers and jackets (Section 4). The performance of these specimens was compared to respective results of elements strengthened with additional RC layers, and the superior performance of beams with three side UHPFRC jacket was highlighted (Section 5).2. Reinforced concrete beams prior to strengthening: Numerical modelling and experimental validationThe Initial, prior to strengthening, Beam (IB) examined in this study is based on a previous experimental program [7]. Initial beam’s cross sectional dimensions were 150 mm by 250 mm and the length was equal to 2200 mm. The reinforcement consisted of two bars with a diameter of 12 mm (2H12) made of steel with a characteristic yielding stress value of 500 MPa in the tensile side with a cover of 25 mm (Fig. 1a). The characteristic cylinder concrete compressive strength of the initial beam at 28 days was found equal to 39.5 MPa. The effective span was equal to 2000 mm and the beam was tested under a four-point bending loading with an imposed deflection rate of 0.008 mm/s. The distance between the two loading points in the middle of the span was equal to 500 mm (Fig. 1b).For the finite element analysis, ATENA software [32] was used. Concrete was simulated with an eight-node element, with nonlinear behaviour and softening branches in both tension and compression using SBETA constitutive model [32]. Theascending compressive branch of this model is based on the formula recommended by CEB-FIP model code 90 [33], while its softening law is linearly descending from the peak stress until a limit compressive strain, which was defined by the plastic displacement and the band size, using the fictitious compression plane model [32] (Fig. 2). In tension, linear ascending branch and exponential softening branch based on the fracture energy needed to create a unit area of a stress free crack were used [32]. In all the analyses smeared crack approach was used [32]. For the simulation of steel bars, linear elements with bilinear behaviour were used. The numerical results (IBnum) are compared to the respective experimental for (IBexp) and the results are presented in Fig. 3[31].From the results presented in Fig. 3, very good agreement between the numerical and the respective experimental results was observed. The same assumptions were used for the modelling of RC layers and beams presented in the following sections.3. Experimental investigation and numerical modelling of UHPFRC3.1. UHPFRC material preparationUHPFRC is a material with enhanced strength in tension and compression and significantly high energy absorption in the post-cracking region. One of the main characteristics of UHPFRC is the enhanced homogeneity which is achieved by using fine aggregates only. In the mix design of the present study, silica sand with maximum particle s ize of 500 μm was used together with silica fume and Ground Granulated Blast Furnace Slag (GGBS). Silica fume, with particle size almost 100 times smaller than cement, improve not only the density of the matrix but also the rheological properties, while GGBS is used as a partial replacement of cement. High steel fibre content (3%) of straight fibres with 13 mm length and 0.16 mm diameter were used. The mix design is presented in Table 1 and it was based on a previous experimental investigation [19].For the preparation of UHPFRC the dry ingredients were mixed first for 3 min in a high shear mixer Zyklos (Pan Mixer ZZ 75 HE), then the water and the superplasticizer were added to the mix and, at the end, the steel fibres were added gradually. The specimens were cured in a steam curing tank at 90 °C for 3 days and the testing was conducted 14 days after casting. These curing conditions were found to be appropriate for the acceleration of the curing, since the strength achieved after 3 days in the steam curing tank (90 °C) was the same with the strength achieved 3 months under normal curing conditions.3.2. Compressive and direct tensile tests and numerical modellingThe standard cube compressive tests (100 mm side) were conducted and the mean compressive strength was found equal to 164 MPa while for the tensile strength, direct tensile tests of 6 dog-bone specimens were carried out (Fig. 4)[34].A constant loading rate of 0.007 mm/s was used to control the tests which is in agreement with the loading rate used by Hassan et al. [19] leading to comparable results. The extension of the specimens was recorded using Linear Variable Differential Transformers (LVDTs). The setup of Fig. 4b was used to measure the average extension over a gauge length of 105 mm, and the stress versus strain(extension normalized to the gauge length) results of all the 6 specimens together with the average curve are presented in Fig. 5[34].4. Numerical modelling of strengthened beams with UHPFRCIn this section, the numerical investigation on beams strengthened with additional layers and jackets is presented. The Initial Beam (IB) was identical to the one described in Section 2, and the same modelling assumptions were used. For the modelling of UHPFRC, the numerical model of Section 3.3 was implemented. The concrete shrinkage was simulated by a negative volumetric strain value to the UHPFRC elements [15]. Shrinkage strain value of 565 microstrains was applied to the elements of the UHPFRC layers and jackets, based on the results presented in Section 3.5 (Fig. 13b).The interface between the Initial Beam (IB) and the UHPFRC was modelled using special two dimensional elements with a coefficient of friction equal to 1.5 and cohesion 1.9 MPa, representing a well-roughened interface [44]. The coefficient of friction used in this study (1.5) is very close to the ultimate value recommended by the Model Code 2010 [45] for very well roughened interfaces (1.4). The reliability of these numerical assumptions were examined in previous studies [46] and [47]. The importance of the concrete-to-concrete shear transfer mechanisms on the overall performance of strengthened elements was also highlighted in a previous study [48]. One of the main aims of the current study is to conduct a critical comparison of the effectiveness of this novel technique with the traditional strengthening method of using additional RC layers. For this purpose, results of a previous investigation on strengthened beams with RC layers were used [7], where roughening of concrete interface was made using an air chipping hammer, and an average roughness of 2–3 mm was achieved. There are published recommended methods to characterise and quantify concrete surface texture [49] and [50]. In this study [7], sand patch test was used. Dowels were not provided, since one of the aims of this study [7] was to investigate if sufficient interface performance can be provided by interface roughening without any mechanical connectors. Also, in case of relatively ‘thin’ layers the use of dowels can’t be easil y applied since a minimum embedment length equal to six times of dowel’s diameter is required [51]. Results showed that when additional RC layer is applied to the compressive side there is no need of steel connectors and, even with not so well roughened interface, the behaviour of the strengthened beam is almost monolithic [7]. In the current study, and since comparisons of the two techniques were made, exactly the same interface conditions were used for the strengthened beams with UHPFRCIn the present study, shrinkage restraint was provided by the connection of the UHPFRC layer with the existing beam, and it was found that shrinkage effect was negligible. However, the effect of restrained shrinkage strain is highly affected by the degree of restraint and by the loading conditions. In previously published studies on strengthened columns with four side jackets [15], [46] and [52], the degree of restraint was much higher and the strength and stiffness of the examined columns were considerably reduced as shrinkage strain values were increased. Furthermore, inprevious studies on monolithic beams [53] and columns [54], it was found that as the reinforcement amount was increased; the additional tensile stresses due to restrained shrinkage were increased, leading to reduced first cracking load values.Numerical analyses were conducted for all the examined techniques (Fig. 14), using initial shrinkage strain value equal to 565 microstrains and four-point bending loading (Fig. 1b). The crack pattern together with the strain distribution at the ultimate strength stage for all the examined specimens is presented in Fig. 16.As it was expected, and based on the results of Fig. 20, the tensile strength of UHPFRC was not affecting the response of specimens strengthened in the compressive side (ST_UHPFR_CS) considerably, since an increment less than 4% in the ultimate moment was observed when UHPFRC tensile strength was increased from 8 MPa to 16 MPa. In case of strengthened specimens with UHPFRC in the tensile side (ST_UHPFR_TS), the ultimate moment was increased by 31% when UHPFRC tensile strength was increased from 8 MPa to 16 MPa. The respective increment for strengthened specimens with three side jackets (ST_UHPFRC_3SJ) was significantly higher and equal to 53%.The effect of the post-peak (softening) stress–strain behaviour of UHPFRC on the overall performance of the strengthened elements was also investigated. The softening behaviour of UHPRC is strongly dependent on the geometry of the fibres and on the fibre orientation and distribution [18]. It has been found that the post-cracking tensile strength can be increased up to 50% using appropriate fibre type and by controlling fibre distribution and orientation [18]. In the current study, two additional stress–strain models were examined using 50% higher and 50% lower post-peak stresses, and the results were compared to the respective of the stress–strain model which was based on the experimental results (Fig. 6). The examined models are presented in Fig. 21 and the respective load–deflection results for specimens strengthened in the tensile side (ST_UHPFR_TS), in the compressive side (ST_UHPFR_CS), and with a three side jacket (ST_UHPFR_3SJ) are illustrated . References[1]E.S. Julio, F. Branco, V.D. Silva Structural rehabilitation of columns with reinforced concrete jacketing J Prog Struct Eng Mater, 5 (2003), pp. 29–37 View Record in Scopus| Full Text via CrossRef | Citing articles (24)[2]E.S. Julio, F. Branco, V.D. SilvaReinforced concrete jacketing—interface influence on monotonic loading response ACI Struct J, 102 (2) (2005), pp. 252–257 View Record in Scopus | Citing articles (20)[3]D. Trikha, S. Jain, S. Hali Repair and strengthening of damaged concrete beams Concr Int Des Constr, 13 (6) (2011), pp. 53–59 View Record in Scopus | Citing articles (1)[4]H.K. Cheon, N. MacAlevey Experimental behaviour of jacketed reinforced concrete beams ASCE J Struct Eng, 126 (2000), pp. 692–699[5]F. AltunAn experimental study of jacketed reinforced concrete beams under bending Constr Build Mater, 18 (2004), pp. 611–618 Article| PDF (404 K)| View Record in Scopus | Citing articles (12)[6]O. Tsioulou, S. Dritsos Α theoretical model to predict interface slip due to bending RILEM Mater Struct, 44 (4) (2011), pp. 825–843 View Record in Scopus| Full Text via CrossRef | Citing articles (4)译文用超高性能纤维增强钢筋混凝土强度（UHPFRC）聚焦•实验研究有助于高强纤维钢筋混凝凝土的力学性能和收缩率论证。

混凝土加固中的纤维增强方法一、引言混凝土加固是目前建筑结构加固中最为常见的方法之一，其主要应用于老化、磨损、承载力下降等问题严重的混凝土结构。

纤维增强混凝土（Fiber Reinforced Concrete，FRC）作为混凝土加固的一种重要手段，具有耐久性强、抗裂性好、耐疲劳性能优越等优点，逐渐成为加固工程中的首选方案之一。

本文将从纤维增强混凝土的定义、种类和特点、纤维增强混凝土加固方法及其应用等方面进行详细阐述。

二、纤维增强混凝土的定义纤维增强混凝土（Fiber Reinforced Concrete，FRC）是一种以混凝土为基础材料，通过加入纤维材料增强混凝土的强度和韧性的新型复合材料。

纤维可以是钢纤维、聚丙烯纤维、玻璃纤维、碳纤维等多种类型的纤维，其加入量一般占混凝土体积的1%-5%。

三、纤维增强混凝土的种类和特点1. 纤维增强混凝土的种类(1) 钢纤维增强混凝土（Steel Fiber Reinforced Concrete，SFRC）：钢纤维增强混凝土是一种以钢纤维为增强材料的混凝土，主要用于加强混凝土的抗拉强度和抗冲击性。

(2) 聚丙烯纤维增强混凝土（Polypropylene Fiber Reinforced Concrete，PFRC）：聚丙烯纤维增强混凝土是一种以聚丙烯纤维为增强材料的混凝土，主要用于加强混凝土的抗裂性和抗渗性。

(3) 玻璃纤维增强混凝土（Glass Fiber Reinforced Concrete，GFRC）：玻璃纤维增强混凝土是一种以玻璃纤维为增强材料的混凝土，主要用于加强混凝土的抗弯强度和韧性。

(4) 碳纤维增强混凝土（Carbon Fiber Reinforced Concrete，CFRC）：碳纤维增强混凝土是一种以碳纤维为增强材料的混凝土，主要用于加强混凝土的抗弯强度和耐久性。

2. 纤维增强混凝土的特点(1) 耐久性强：纤维增强混凝土的耐久性强，能有效延长混凝土结构的使用寿命。

碳纤维增强复合材料加固混凝土结构技术规程碳纤维增强复合材料加固混凝土结构技术规程在这篇文章中，我将深入探讨碳纤维增强复合材料（Carbon Fiber Reinforced Polymer，简称CFRP）在加固混凝土结构中的应用，以及相关的技术规程。

CFRP是一种由碳纤维和树脂组成的材料，具有优异的抗张强度和刚度。

它已被广泛应用于建筑、桥梁和道路等领域，用于加固和修复老化或受损的混凝土结构。

通过引入CFRP材料，可以有效提高混凝土结构的承载能力和抗震性能。

下面，我将按照从简到繁、由浅入深的方式来逐步介绍碳纤维增强复合材料加固混凝土结构的技术规程。

1. 介绍先来简单介绍一下碳纤维增强复合材料和混凝土结构的基本知识。

碳纤维增强复合材料是由碳纤维和树脂基体组成的复合材料，具有超强的拉伸强度和刚度。

而混凝土结构是一种常见的建筑结构材料，用于建造房屋、桥梁和基础等。

2. 加固原理介绍碳纤维增强复合材料在加固混凝土结构中的原理。

CFRP材料可以通过粘结在混凝土表面或灌浆进裂缝中，与混凝土共同工作，增加结构的强度和刚度。

CFRP材料还可以提供一定的防腐和耐久性。

3. 加固方法详细介绍碳纤维增强复合材料加固混凝土结构的方法。

包括表面粘贴、外包围、梁加固等。

每种方法都会根据结构的具体情况选择合适的加固方法。

4. 技术规程介绍碳纤维增强复合材料加固混凝土结构的技术规程。

这些规程包括材料的选用、施工工艺、加固层厚度和粘接性能等方面。

这些规程是为了确保加固效果和工程质量，需要严格遵守。

5. 加固效果评估讲解如何对加固效果进行评估。

主要包括载荷试验和监测技术。

通过对加固结构进行载荷试验，可以评估加固后的结构承载能力是否达到设计要求。

监测技术可以实时监测结构的变形和应力。

6. 应用案例展示一些实际应用案例，以便读者更好地理解碳纤维增强复合材料加固混凝土结构的实际效果。

包括桥梁加固、建筑物加固和道路加固等方面。

总结：通过本文的深入探讨，我们了解到碳纤维增强复合材料加固混凝土结构的技术规程。

本科毕业设计（论文）英文专题专业名称：土木矿建年级班级：土木单招06-1班学生姓名：XXX指导教师：余永强河南理工大学土木工程学院二○一○年六月十日Reinforcement of concrete beam–column connectionswith hybrid FRP sheetAbstractThe paper describes the results of tests on prototype size reinforced concrete frame specimens which were designed to represent the column–beam connections in plane frames. The tests were devised to investigate the influence of fibre reinforced plastic (FRP reinforcement applied to external surfaces adjacent to the beam–column connection on the behaviour of the test specimens under static loading. Of particular interest under static loading was the influence of FRP reinforcement on the strength and stiffness of beam–column connection. As a key to the study, the hybrid FRP composites of E-glass woven roving (WR) and plain carbon cloth, combined with chopped strand mat (CSM), glass fiber tape (GFT) with a vinyl-ester resin were designed to externally reinforce the joint of the concrete frame. The results show that retrofitting critical sections of concrete frames with FRP reinforcement can provide signification strengthening and stiffening to concrete frames and improve their behaviour under different types of loading. The selections of types of FRP and the architecture of composites in order to improve the bonding and strength of the retro-fitting were also discussed.Author Keywords: Concrete structure; Strengthening; Rehabilitation; Hybrid FRP composite; Wrapping technique1. IntroductionA widely adopted technique for retrofitting concrete structure is to use steel jackets placed around existing concrete columns [1 and 2]. The use of steel encasement to provide lateral confinement to the concrete in compression has been studied extensively[3 and 4], and has shown increase in the compression load carrying capacity and ductility of the concrete columns. However, the shortcomings of this technique are that it suffers from corrosions as well as inherent difficulties during practical applications. Fibre reinforced plastic (FRP), on the other hand, is increasingly being used to reinforce concrete, masonry and timber structures. The load carrying capacity and serviceability of existing structures can be significantly augmented through externally retrofitting critical sections with FRP sheeting. In recent years FRP materials with wide range of fibre types of glass, aramid or carbon provide designers with an adaptable and cost-effective construction material with a large range of modulus and strength characteristics. Comparing with traditional rehabilitation techniques, the FRP composites have high specific strength/stiffness, flexibility in design and replacement as well as robustness in unfriendly environments. With FRP composites it is possible and also necessary to achieve the best strengthening results by optimising the constitute materials and architecture. Optimisation of the constitute materials and architecture becomes essential in order to utilise the superiority of FRP composites in application of rehabilitation [5, 6, 7, 8 and 9]. It was found that winding of carbon fiber/epoxy composites around square concrete columns can increase the load carrying capacity by 8–22%, depending on the amount of fibres used and treatments of substrate surface [10]. The use of resin infusion technique was shown to contribute to substantial improvements in composite wrapping efficiency, and the use of woven glass roving, as the reinforcement in composites wrapping, was found to significantly increase both load carrying capacity and deformation resistance capacity of the concrete stubs [2]. Furthermore, through the use of glass/carbon hybrid reinforcements with an epoxy resin, replication of initial performance of concrete stubs subjected to deterioration was shown possible, with a simultaneous further improvement in load carrying capacity. In terms of the effects of orientation and thickness of the composites warps, it was found that the predominant use ofreinforcements in the hoop direction would result in high efficiency [11]. Despite the large number of research carried out, one shortcoming of most studies has been that they were limited to simple small size components, such as concrete cylinders, rather than real structures. Furthermore, it is essential to study the optimisation of composites architectures in terms of cost effectiveness including materials and processing methods. This implies that the reinforcement of infrastructure with FRP composites should utilise the advantages of various materials, not only carbon fibers with epoxy resin, but also glass fiber or hybrid of carbon/glass fibres with other polymer resins. In this experimental investigation, a hybrid of carbon/E-glass with vinyl-ester resin composites jacket was designed to reinforce a typical building components, namely a column–beam connection. Static tests were then conducted on FRP reinforced and non-reinforced specimens with extensive instrumentation to study the influence of the designed composite reinforcement. The investigation reported in the paper forms part of a collaborative research program between the University of Technology, Sydney and the Centre for Advanced Materials Technology, the University of Sydney in relation to application of advanced fibre composites to strengthen, stiffen and hence rehabilitate concrete structures.2. Experimental proceduresThree prototype size reinforced concrete frame specimens, representing typical concrete column–beam connection, were designed for this study. Geometry of the specimens with location of FRP composite reinforcement is illustrated in Fig. 1. Among three specimens, two of them are as-is concrete beam–column connection type (none composites-reinforced (Non-CR) specimens) and one specimen was reinforced by the hybrid of carbon fiber and glass fibre composites around the column–beam joint (composites-reinforced (CR) specimen). All three specimens were pre-cast using standard commercial mix grade 40 concrete. The steel reinforcement of the concrete specimens are also shown in Fig. 1. Concrete compression tests based on the Australian Standard (AS 1012–1986) were conducted on the samples taken during the concrete pour in order to determine the modulus of elasticity and ultimate compression strength (UCS) of the concrete.2.1. Composites architectureOne of the three concrete frame specimens was reinforced with hybrid composites. The hybrid composites consists of four basic architectures, namely E-glass woven roving (WR/600 g/m2), chopped strand mat (CSM-300 g/m2), carbon cloth (plain weave-200 g/m2) and glass fibre tape (GFT-250 g/mm2). The details of the composites architecture are shown in Table 1 and Fig. 2. Details of lay-up are illustrated in Fig. 3. WR and carbon cloth are a multi-directional reinforcement with biaxial plain weaving which provide equivalent strength in both axial and hoop directions. They play the basic reinforcement role in this composites architecture. GFT applying at hoop direction provides very good confinement and enhances structural integrity. The selection of resin curing systems is mainly concerned with the resin gel-time at ambient temperature, which is critical to wrapping process. In general, cold setting resin systems (ambient temperature curing) can be used when wet lay-up process is applied. Since no lay-up machine is available for the wrapping process described in this study, the hand lay-up method was used. The vinyl-ester resin, Dastar-R/VERPVE/SW/TP, was mixed with 1.5% of MEKP(methyl-ethyl-ketone-peroxide), 0.4% of CoNap (Cobalt napthenate), and 0.5% of DMA(Dimethylaniline) at ambient temperature. The resin cures at ambient temperature. The weight ratio between resin and fibre layers was 1:1.5 for WR/CSM layers and 1:0.8 for carbon cloth, respectively. The concrete frame was wrapped by a lames-wool roller and a consolidating roller. Before laying the first fibre layer, the concrete surfaces were cleaned up using acetone, and a thin resin coat was applied to seal micro holes on the surface of concrete columns. However, further surface treatment such as sanding surface to expose the aggregates was intentionally avoided. Each composite layer was wetted with the resinand rolled onto the concrete frame to ensure full consolidation.Table 1. Details of five composite systems with a compositearchitectures2.2. Design of static testsThe static tests of the concrete frame specimens were setup in a horizontal plane. The three supports of the concrete frame (no load applied) were roller type as shown in Fig. 4. The end at which load was applied was also a roller type support, however, horizontal movements were obviously not prevented. In order to provide the ideal roller type boundary conditions at each end as designed, a special setup was developed with combination of rollers and a swivel head at each supporting/loading point (Fig. 5). Four 1000-kN-hydraulic jacks were used in the tests. Among them, the only active jack was the jack that applied loads, while others were simply acting as adjustable packing to providing the reactions.Fig. 4. Illustrative sketch of test set-up for static test.Fig. 5. Set-up for static test of concrete frame.2.3. Instrumentation and data loggingApplied load as well as reaction forces were measured using four 998.8 kN load cells located in each of four supporting/loading positions. In order to obtain detailed flexural deflection curves for the concrete frame specimens, twelve linear variable displacement transducers (LVDTs) with a range from ±2.5 to ±50 mm were used at strategic locations to measure the flexural deflections. Extensive strain gauging was designed to capture the stress distribution of the testing specimens in order to validate tests and gain an insight into the behaviour of the concrete frame with or without FRP reinforcement. The total number of strain gauges was 56 for each specimen, in which 28 strain gauges (5 mm) were located on steel rebars and the rest (30 mm strain gauges) were located on the external surface of the concrete frame specimens. Locations of the strain gauges were arranged so that the strains on various points of the cross sections could be captured. A typical strain gauge arrangement for most measured cross sections is shown in Fig. 6. Locations of strain gauges inside the section are shown in Fig. 7.Fig. 6. Location of cross sections of the concrete frame for strain gauging.2.4. Test procedureDesignations of test specimens and a brief description are given in Table 2. Prior to being formally tested at service load level, the first non-CR specimen was subjected to a series of investigative tests mostly loaded at the service load level of 40 kN with one single overload up to 50 kN. The second non-CR specimen and the CR specimens were not subjected to any loading until the initial service load level tests. All ultimate load tests were conducted after every specimen was exposed to about 100 cycles of cyclic loading atservice load levels.Table 2. Applied load and reactions for typical tests (unit: kN)3. Results and analysisIn order to determine the influence of FRP composites, five sets of tests were conducted on the three specimens including three tests at service load levels and two atthe ultimate load level. For every test, logged data consisted of four load records, twelve deflection records and 56 or 64 strain records.3.1. Validation of the static testsTo validate the performed tests, the static equilibrium for each test was verified as follows:Equilibrium of external loads: As redundancy was avoided in design of these tests and load cells were placed at each loading or reaction point, it was convenient to check equilibrium of the load/reaction forces through simple statics. Table 2 shows that the equilibrium of external loads was satisfied.Equilibrium of forces and equilibrium of moment on cross sections: In order to calculate the internal forces and sectional moments, strains on the designated sections were required. To process the measured strains on a given cross section, the following assumption was made: the strains vary linearly through the cross sections. In other words the strains at a given cross section can be represented by a strain plane. Under this assumption, least square method with the two explanatory variables was adopted to obtain the strain plane for each given cross section using values of six measured strains. Fig. 8 shows comparison of the measured strain values and those calculated from the least square fitting. The strain values used in subsequence evaluations or calculations were obtained from calculated strain planes. For the validation of the equilibrium of internal forces in a given cross section, forces were calculated by integration of resulting stresses in tension and compression zones, respectively. The concrete was assumed to carry only compression loads and steel rebars (with FRP composites in some cases) were considered as the main load carriers in the tension zone. Equilibrium states that the resultant force in the compression zone should be equal to that in the tension zone. Moments at a given cross section were firstly calculated through integration of stresses in the section. They were compared to those calculated by using measured loads multiplied by the lever arms.Details of formulae pertained to these calculations are presented in Appendix A. As shown in Table 3 and Table 4, equilibrium is validated.Fig. 8. Comparison of measured vs calculated strain values from least square fitting.Table 3. List of calculated internal force and moments at section A-A of a non-CRspecimenTable 4. List of calculated internal force and moments at section A-A of a CR specimen3.2. Load–deflection curvesComparison of load–deflection curves for CR and non-CR specimens at both service load and ultimate load levels are shown in Fig. 9 and Fig. 10. About 45% increase in stiffness was observed due to the presence of FRP composites reinforcement (service load level). Results of the ultimate loading test indicated an increase in load carrying capacity of CR specimen of approximately 30% due to the presence of FRP composites.3.3. Analysis of the strain resultsTo evaluate change of strain in steel rebars due to FRP reinforcement, a parameter was defined, namely "average strain reduction". It is defined aswhere P is the average of maximum section strains of the two none composites-reinforced (non-CR) specimens and R is the maximum section strain of composites-reinforced (CR) specimen at the same load level. Table 5 and Table 6 summarise the typical comparison of maximum/minimum strains between non-CR and CR specimens and average strain reduction in various cross sections at same load level (see also Fig. 11). If one takes the mean of the average strain reductions for all beam-sections, it yields strain reduction factor of 51%. In same way, the mean of the average strain reductions for all column-sections is 55%. The average strain reduction can be used as an indication of external FPR reinforcement efficiency.Table 5. Comparison of the maximum strains in the rebars for beam sections (unit: )Table 6. Comparison of the maximum strains in the rebars for column sections (unit:)Fig. 11. Comparison of strains of CR and non-CR specimens in steel rebars at a given section.3.4. Discussions on applied composites architectureResults from both service load level tests and ultimate load test of the concrete frames show that the proposed composites architecture successfully enhanced the original structure in terms of stiffness and load carrying capacity. It is interesting to note that although the elastic modulus of FRP composites is only approximately half of that of concrete, the increase in stiffness and load carrying capacity of a reinforced concrete was significant. Despite of absence of special surface treatment of concrete before the application of FRP composite reinforcement, the bonding between the concrete and composites did not fail. This may be owing to the lower elastic modules of hybrid composites. There is an indication that low modulus FRP may provide better reinforcement/retrofitting for concrete structures because of low tensile strength in concrete. In the lay-up design, the gradual change of thickness is essential. It will reduce possible stress concentration in the FRP composites which could cause delamination or cracking. However, it is important to point out that because only a limited number of specimens were studied, some of these conclusions may be biased. It is suggested to conduct more tests to confirm these results.4. ConclusionsAs results of this study, the following conclusions can be drawn:1. Tests on prototype size reinforced concrete frame specimens, designed to represent the column–beam connections in plane frame, have been successfully conducted. Test results were validated through equilibrium checks.2. Designed hybrid composites consisting of roving cloth, carbon cloth, and chapped strand mat and glass fibre tape demonstrated effectiveness in reinforcing concrete structures. The results from the tests show significant increases in stiffness and load carrying capacity due to reinforcement provided by hybrid FRP composites. The resultsalso show that optimisation is important in reinforcing concrete structures to achieve good results with low cost.3. The results of static tests also suggest that hybrid carbon/E-glass fibre composites with low elastic modulus may contribute to good bonding and non-delamination. However, this needs to be confirmed by more tests.4. It is also suggested that further investigation be carried out including reinforcing damaged concrete frame specimens, cyclic loading and using different composites architectures.Appendix AAssuming that at a given cross section of beam/column strain distribution is linear, for the given section, strain can then be expressed in form of(x ,y )=ax +by +c ,(A .1) where a , b , c are constants.Consider a two explanatory variables regression modelYi =0+1x i 1+2x i 2+e i , (A.2)where x i 1 represents the i th observation on explanatory variable X 1 and x i 2 denotes the i th observation on second explanatory variable X 2.One can obtain a best fit strain plane from measured strain in a given section.Under linear strain distribution assumption, a closed form solutionfor force and moment at the cross section using strain data can be obtained by double integration. In compression zone for the concrete (refer to Fig. 12), one obtains:(A.3)where E is the modulus of the elasticity of concrete; a , b and c are constants in Eq.(A.1); F I is the resultant force in the compression zone.(A.4)where M I is the moment at the compression zone.Fig. 12. Schematic drawing of a typical cross sectionof concrete frames. For steel rebars and composites (if applied):(A.5)where F I S and F I C are forces in steel rebars and composite, respectively. In tension zone, only steel rebars and composite count, formulae are similar to Eq. (A.5).具有混合纤维增强塑料片的混凝土梁–柱联接部位的加固摘要本篇文章描述了对加固后标准尺寸混凝土结构试件进行试验的结果，该试件代表平面框架结构中的梁–柱联接部位。