Trengthening And Rehabilitation Of Civil Infra Tructureu Ing Fibre Reinforced Polymer Pdf
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Reviewed: October 24th Published: January 23rd
- Fiber Reinforced Composites – Advanced Materials for the Renewal of Civil Infrastructure
- Rehabilitation of Concrete Structures with Fiber-Reinforced Polymer
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Reviewed: October 24th Published: January 23rd Fibre-reinforced polymer FRP , also Fibre-reinforced plastic , is a composite material made of a polymer matrix reinforced with fibres.
The fibres are usually glass, carbon, or aramid, although other fibres such as paper or wood or asbestos have been sometimes used. The polymer is usually an epoxy, vinylester or polyester thermosetting plastic, and phenol formaldehyde resins are still in use. FRPs are commonly used in the aerospace, automotive, marine, and construction industries. Composite materials are engineered or naturally occurring materials made from two or more constituent materials with significantly different physical or chemical properties which remain separate and distinct within the finished structure.
Most composites have strong, stiff fibres in a matrix which is weaker and less stiff. The objective is usually to make a component which is strong and stiff, often with a low density. Commercial material commonly has glass or carbon fibres in matrices based on thermosetting polymers, such as epoxy or polyester resins. Sometimes, thermoplastic polymers may be preferred, since they are moldable after initial production. There are further classes of composite in which the matrix is a metal or a ceramic.
For the most part, these are still in a developmental stage, with problems of high manufacturing costs yet to be overcome [ 1 ]. Furthermore, in these composites the reasons for adding the fibres or, in some cases, particles are often rather complex; for example, improvements may be sought in creep, wear, fracture toughness, thermal stability, etc [ 2 ]. Fibre reinforced polymer FRP are composites used in almost every type of advanced engineering structure, with their usage ranging from aircraft, helicopters and spacecraft through to boats, ships and offshore platforms and to automobiles, sports goods, chemical processing equipment and civil infrastructure such as bridges and buildings.
The usage of FRP composites continues to grow at an impressive rate as these materials are used more in their existing markets and become established in relatively new markets such as biomedical devices and civil structures.
A key factor driving the increased applications of composites over the recent years is the development of new advanced forms of FRP materials. This includes developments in high performance resin systems and new styles of reinforcement, such as carbon nanotubes and nanoparticles. This book provides an up-to-date account of the fabrication, mechanical properties, delamination resistance, impact tolerance and applications of 3D FRP composites [ 3 ].
FRP composites are lightweight, no-corrosive, exhibit high specific strength and specific stiffness, are easily constructed, and can be tailored to satisfy performance requirements. Due to these advantageous characteristics, FRP composites have been included in new construction and rehabilitation of structures through its use as reinforcement in concrete, bridge decks, modular structures, formwork, and external reinforcement for strengthening and seismic upgrade [ 4 ].
The applicability of Fiber Reinforced Polymer FRP reinforcements to concrete structures as a substitute for steel bars or prestressing tendons has been actively studied in numerous research laboratories and professional organizations around the world. FRP reinforcements offer a number of advantages such as corrosion resistance, non-magnetic properties, high tensile strength, lightweight and ease of handling.
However, they generally have a linear elastic response in tension up to failure described as a brittle failure and a relatively poor transverse or shear resistance. They also have poor resistance to fire and when exposed to high temperatures. They loose significant strength upon bending, and they are sensitive to stress-rupture effects.
Moreover, their cost, whether considered per unit weight or on the basis of force carrying capacity, is high in comparison to conventional steel reinforcing bars or prestressing tendons. From a structural engineering viewpoint, the most serious problems with FRP reinforcements are the lack of plastic behavior and the very low shear strength in the transverse direction. Such characteristics may lead to premature tendon rupture, particularly when combined effects are present, such as at shear-cracking planes in reinforced concrete beams where dowel action exists.
The dowel action reduces residual tensile and shear resistance in the tendon. Solutions and limitations of use have been offered and continuous improvements are expected in the future. The unit cost of FRP reinforcements is expected to decrease significantly with increased market share and demand. However, even today, there are applications where FRP reinforcements are cost effective and justifiable. Such cases include the use of bonded FRP sheets or plates in repair and strengthening of concrete structures, and the use of FRP meshes or textiles or fabrics in thin cement products.
The cost of repair and rehabilitation of a structure is always, in relative terms, substantially higher than the cost of the initial structure. Repair generally requires a relatively small volume of repair materials but a relatively high commitment in labor. Moreover the cost of labor in developed countries is so high that the cost of material becomes secondary. Thus the highest the performance and durability of the repair material is, the more cost-effective is the repair. This implies that material cost is not really an issue in repair and that the fact that FRP repair materials are costly is not a constraining drawback [ 5 ].
When considering only energy and material resources it appears, on the surface, the argument for FRP composites in a sustainable built environment is questionable.
However, such a conclusion needs to be evaluated in terms of potential advantages present in use of FRP composites related to considerations such as:. In the case of FRP composites, environmental concerns appear to be a barrier to its feasibility as a sustainable material especially when considering fossil fuel depletion, air pollution, smog, and acidification associated with its production.
In addition, the ability to recycle FRP composites is limited and, unlike steel and timber, structural components cannot be reused to perform a similar function in another structure. However, evaluating the environmental impact of FRP composites in infrastructure applications, specifically through life cycle analysis, may reveal direct and indirect benefits that are more competitive than conventional materials.
Composite materials have developed greatly since they were first introduced. However, before composite materials can be used as an alternative to conventional materials as part of a sustainable environment a number of needs remain. Availability of standardized durability characterization data for FRP composite materials. Integration of durability data and methods for service life prediction of structural members utilizing FRP composites.
Development of methods and techniques for materials selection based on life cycle assessments of structural components and systems. Ultimately, in order for composites to truly be considered a viable alternative, they must be structurally and economically feasible.
Numerous studies regarding the structural feasibility of composite materials are widely available in literature [ 6 ]. However, limited studies are available on the economic and environmental feasibility of these materials from the perspective of a life cycle approach, since short term data is available or only economic costs are considered in the comparison. Additionally, the long term affects of using composite materials needs to be determined.
The byproducts of the production, the sustainability of the constituent materials, and the potential to recycle composite materials needs to be assessed in order to determine of composite materials can be part of a sustainable environment. Therefore in this chapter describe the physicochemical properties of polymers and composites more used in Civil Engineering. The theme will be addressed in a simple and basic for better understanding.
The synthetic polymers are generally manufactured by polycondensation, polymerization or polyaddition. The polymers combined with various agents to enhance or in any way alter the material properties of polymers the result is referred to as a plastic.
The Composite plastics can be of homogeneous or heterogeneous mix. Composite plastics refer to those types of plastics that result from bonding two or more homogeneous materials with different material properties to derive a final product with certain desired material and mechanical properties. The Fibre reinforced plastics or fiber reinforced polymers are a category of composite plastics that specifically use fibre materials not mix with polymer to mechanically enhance the strength and elasticity of plastics.
The original plastic material without fibre reinforcement is known as the matrix. The matrix is a tough but relatively weak plastic that is reinforced by stronger stiffer reinforcing filaments or fibres. The extent that strength and elasticity are enhanced in a fibre reinforced plastic depends on the mechanical properties of the fibre and matrix, their volume relative to one another, and the fibre length and orientation within the matrix.
Reinforcement of the matrix occurs by definition when the FRP material exhibits increased strength or elasticity relative to the strength and elasticity of the matrix alone. Polymers are different from other construction materials like ceramics and metals, because of their macromolecular nature. The covalently bonded, long chain structure makes them macromolecules and determines, via the weight averaged molecular weight, Mw, their processability, like spin-, blow-, deep draw-, generally melt-formability.
The number averaged molecular weight, Mn, determines the mechanical strength, and high molecular weights are beneficial for properties like strain-to-break, impact resistance, wear, etc.
Thus, natural limits are met, since too high molecular weights yield too high shear and elongational viscosities that make polymers inprocessable. The resulting mechanical properties of these high performance fibers, with moduli of GPa and strengths of up to 4 GPa, represent the optimal use of what the potential of the molecular structure of polymers yields, combined with their low density.
Thinking about polymers, it becomes clear why living nature used the polymeric concept to build its structures, and not only in high strength applications like wood, silk or spider-webs [ 7 ].
The linking of small molecules monomers to make larger molecules is a polymer. Polymerization requires that each small molecule have at least two reaction points or functional groups. There are two distinct major types of polymerization processes, condensation polymerization, in which the chain growth is accompanied by elimination of small molecules such as H 2 O or CH 3 OH, and addition polymerization, in which the polymer is formed without the loss of other materials.
There are many variants and subclasses of polymerization reactions. The polymer chains can be classified in linear polymer chain, branched polymer chain, and cross-linked polymer chain. If n is a small number, 2—10, the products are dimers, trimers, tetramers, or oligomers, and the materials are usually gases, liquids, oils, or brittle solids.
In most solid polymers, n has values ranging from a few score to several hundred thousand, and the corresponding molecular weights range from a few thousand to several million. The end groups of this example of addition polymers are shown to be fragments of the initiator. If only one monomer is polymerized, the product is called a homopolymer.
The polymerization of a mixture of two monomers of suitable reactivity leads to the formation of a copolymer, a polymer in which the two types of mer units have entered the chain in a more or less random fashion. If chains of one homopolymer are chemically joined to chains of another, the product is called a block or graft copolymer. Isotactic and syndiotactic stereoregular polymers are formed in the presence of complex catalysts, or by changing polymerization conditions, for example, by lowering the temperature.
The groups attached to the chain in a stereoregular polymer are in a spatially ordered arrangement. The regular structures of the isotactic and syndiotactic forms make them often capable of crystallization. The crystalline melting points of isotactic polymers are often substantially higher than the softening points of the atactic product.
The spatially oriented polymers can be classified in atactic random; dlldl or lddld, and so on , syndiotactic alternating; dldl, and so on , and isotactic right- or left-handed; dddd, or llll, and so on. For illustration, the heavily marked bonds are assumed to project up from the paper, and the dotted bonds down. Thus in a fully syndiotactic polymer, asymmetric carbons alternate in their left- or right-handedness alternating d, l configurations , while in an isotactic polymer, successive carbons have the same steric configuration d or l.
Among the several kinds of polymerization catalysis, free-radical initiation has been most thoroughly studied and is most widely employed.
Atactic polymers are readily formed by free-radical polymerization, at moderate temperatures, of vinyl and diene monomers and some of their derivatives. Some polymerizations can be initiated by materials, often called ionic catalysts, which contain highly polar reactive sites or complexes. The term heterogeneous catalyst is often applicable to these materials because many of the catalyst systems are insoluble in monomers and other solvents.
These polymerizations are usually carried out in solution from which the polymer can be obtained by evaporation of the solvent or by precipitation on the addition of a nonsolvent. A distinguishing feature of complex catalysts is the ability of some representatives of each type to initiate stereoregular polymerization at ordinary temperatures or to cause the formation of polymers which can be crystallized [ 1 , 6 ]. Polymerization, emulsion polymerization any process in which relatively small molecules, called monomers, combine chemically to produce a very large chainlike or network molecule, called a polymer.
The monomer molecules may be all alike, or they may represent two, three, or more different compounds. Usually at least monomer molecules must be combined to make a product that has certain unique physical properties-such as elasticity, high tensile strength, or the ability to form fibres-that differentiate polymers from substances composed of smaller and simpler molecules; often, many thousands of monomer units are incorporated in a single molecule of a polymer.
The formation of stable covalent chemical bonds between the monomers sets polymerization apart from other processes, such as crystallization, in which large numbers of molecules aggregate under the influence of weak intermolecular forces. Two classes of polymerization usually are distinguished.
Fiber Reinforced Composites – Advanced Materials for the Renewal of Civil Infrastructure
Fiber reinforced polymer matrix composite materials hitherto used predominantly in aerospace and marine applications are increasingly being considered for use in the renewal of civil infrastructure ranging from the seismic retrofit of bridge columns and the strengthening of parking garage floor slabs to their use in replacement bridge decks and in new bridge structures. Their corrosion resistance, potentially high overall durability, light weight, tailorability and high specific performance attributes enable their use in areas in which the use of conventional materials might be constrained due to durability, weight or lack of design flexibility. This paper provides an overview of the use of composites in the renewal of civil structures with particular emphasis on bridges and pipelines. Examples of large scale testing for the validation of structural effectiveness are given and future design and research advances are presented. This is a preview of subscription content, access via your institution. Rent this article via DeepDyve.
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Rehabilitation of Concrete Structures with Fiber-Reinforced Polymer
The research of new and better performing materials in such fields is somewhat limited by practical and economical constrains and, as a matter of fact, is confined to an academic argument. Their success is due to a variety of different properties, such as high specific strength and specific stiffness, high durability against corrosion, lower weight, ease of installation, and reduced manufacture time. All these latter properties make FRP preferred to traditional construction materials, such as steel and concrete. Nevertheless, there are several aspects of this relatively new technology that still need further research and development, particularly concerning their durability.
The repair of deteriorated, damaged and substandard civil infrastructures has become one of the most important issues for the civil engineer worldwide. This important book discusses the use of externally-bonded fibre-reinforced polymer FRP composites to strengthen, rehabilitate and retrofit civil engineering structures, covering such aspects as material behaviour, structural design and quality assurance. The first three chapters of the book review structurally-deficient civil engineering infrastructure, including concrete, metallic, masonry and timber structures.
This paper aims to analyze the performance of reinforced concrete RC beams strengthened in shear with carbon fiber-reinforced polymer CFRP sheets subjected to four-point bending. ANSYS software is used to build six models. A comparative study between the nonlinear finite element and analytical models, including the ACI The comparative study of the nonlinear finite element results with analytical models shows that the difference between the predicted load capacity ranges from 4.
The s saw the start of rapid economic growth, industrialisation and urbanisation in Korea, resulting in massive construction efforts of both buildings and civil infrastructure projects. These structures are now close to 40 years old and much of the reinforced concrete RC used is their construction is obsolete. They thus now require significant structural reinforcement and rehabilitation to extend their service life in order to save natural resources and minimise negative environmental impacts.