The Use of Fibre Reinforced Polymers in Strengthening Beams in the UK - Essay Example

?    The use of fibre reinforced polymers (FRP) in strengthening beams in the U.K       Discussion and Conclusion The research on FRP technology has revealed that FRP technology is very significant in construction and repair works in the UK and other parts of the world that have adopted the technology. FRP composites are advantageous over other types of materials in a number of ways including: High specific Strength and Stiffness The literature review has reviewed that FRP materials provide significant enhancement in terms of strength-to-weight and stiffness-to-weigh ratios. The material composites reinforced with carbon fibers have a higher tensile strength when compared to other materials. CFRP materials are thus very effective in areas exhibiting strong tensile forces. Although the tensile strength of steel is higher than that of FRP materials, steel is much stiffer and inappropriate to use in areas requiring some mobility. CFRP materials are less fragile and are able to absorb more shear forces compared to steel plates (Feih and Mouritz, 2012). These characteristics enable the designers to create products that are lesser in weight and in thickness. Corrosion resistance FRP materials have high abilities to resist corrosion compared to other materials including steel. This makes them appropriate to use in situations where corrosion is a concern for instance in the construction of bridges. Using FRP composites in outdoor applications thus guarantees long life and lesser expenses concerning maintenance. Enhanced Fatigue Life FRP materials are resistant to fatigue and thus enable engineers to design flexible structures. The ability to absorb stress allows structures to have long life. This makes the FRP materials appropriate to apply in construction of bridges decks and the strengthening of bridges. Ease of transportation and installation FRP materials are easier to transport to installation points comparing the length construction and installation durations. The FRP materials are light in weight and flexible thus enabling engineers to design the products in different places from their installation points. The designers can also customize the components according to the desired forms courtesy of their lightweight and flexibility (Feih and Mouritz, 2012). Tailored characteristics FRP materials are flexible to use and customize according to the required design. Materials such as steel and concrete offer extra strength and stiffness that intrinsically compel the application of isotopic structural designs. In addition, the extra axial stiffness normally results to distress to attraction of forces in instances of seismic attacks. The FRP materials have an enhanced efficiency and viability even in seismic prone areas (Feih and Mouritz, 2012). Sustainability The application of glass-fiber FRP materials is characterized as sustainable and environment-friendly. In terms of energy consumption, the quantity of energy required to produce steel or aluminum is far much greater than that required for the production of FRP composites. Electromagnetic conduction FRP composites are non-conductors of electricity and can thus be applied in constructions around regions prone to electric shock including bridges in factories and along railway transactions. Disadvantages of FRP composites Although FRP composites have numerous advantages that make them ideal to use for construction work, they still have some setbacks, which make their application an issue. One of the disadvantages is that FRP composites are expensive compared to conventional materials such as girder. They are expensive in the short-term though if well maintained the long-term costs are negligible. FRP materials are guaranteed to long life. Although their application is easier and quicker, their lifespan can be short-lived when subjected to unfavorable environmental conditions (Feih and Mouritz, 2012). Applications of FRP The literature review has revealed various areas of application of the FRP technology. Some of the areas are validated by the case studies mentioned in the paper. Some of the areas of FRP application include: Repair and Retrofitting of existing bridges Externally bonded FRP composites are used in strengthening and retrofitting of bridges in the UK and other parts of the world. FRP applied for strengthening and retrofitting is customized into FRP strips or sheet based on the nature of application. Externally bonded FRP materials have been applied for enhancing both flexural and shear ability of concrete constituents such as girders, beams and slabs. Some of the methods of such applications of external FRP enhancement include adhesive bonding, hand lay-up and resin infusion (Harichandran and Baiyasi, 2000). They can also be applied in seismic retrofitting of enhanced concrete bridges in the structure of wrapped column. An example of this application is the Acton Bridge. The retrofitting technique used in construction of this bridge was aimed at enhancing the cyclical loading abilities of the loading beam to overcome fatigue. The CFRP material used in the strengthening of the bridge had a high tensile strength to accommodate the stress associated with associated load (Harichandran and Baiyasi, 2000). Reinforcement of concrete Another application of FRP is in the strengthening of steel reinforcement in concrete structures to safeguard it from extreme weather conditions that catalyze carbonation of concrete and the development of hydrated ferrous oxide of steel. An example of this application is the reinforcement of the Heritage building. Designers studied the building, investigated the environmental factors acting on the building, and decided to use FRP technology to reinforce the original steel enhanced concrete beams. The contract to strengthen and repair the building was conducted by M/S Taylor Woodrow of London UK (Harichandran and Baiyasi, 2000) Hybrid bridge structures This type of application involves the integration of traditional elements such as girders with the modern FRP composites. The main idea behind the use of this technique is to solve the economic challenge created by the use of FRP technology alone. All-Composite Bridge structures This method involves the use of FRP composites alone in the construction of bridges. The first bridge constructed using this technology was the Miyun Bridge in China built in 1982. In the UK, the Aberfeldy Foot Bridge spanning more than 60 meters confirms the success of this technology. The bridge links the Aberfeldy golf course over the River Tay with five holes being on one side and the other four being on the other side. The Aberfeldy Foot bridge (Picture Courtesy: Skinner J.M., University of Bath The significance of the use of FRP in bridges in the UK The FRP technology has been very effective in the construction and strengthening of bridges in the UK. Some of the advantages of FRP composites over other materials in this construction work are that the FRP material is highly economical and appropriate for upgrading and enhancing existing structures including bridges. The use of FRP material is easier and cheaper to deploy and besides it lessens disturbance and installation periods. The application of FRP technology is significant as evidence by its use in several successful projects. Some of the projects that the technology has been a success include: Acton Railway Bridge This is one of the underground bridges constructed in the UK more than 50 years ago. The bridges have undergone corrosion, which has destroyed the main support beams. The bridge is very significant because it links South and North Acton. The Acton Bridge was strengthened via the FRP technology (Han and Chung, 2011). Photograph of the Acton Station (from local sources) Existing repair work to TFL bridges TFL bridges have always been repaired and records maintained to ensure that they are in good condition. The City of London and Transport of London keep a watchful eye on all bridges in the UK to ensure that they are properly maintained and function. The London Permit scheme assists the TFL in ensuring that bridges are functional and in good condition. In particular, the scheme focuses on individual security and safety and thus ensures that bridges are maintained to avert any tragedy. The scheme also encourages the application of innovative ideas in repair and maintenance of bridges to enhance safety (Han and Chung, 2011). Alternatives to FRP FRP technology is difficult to replace or substitute because FRP composites have unique characteristics that make their applications suitable for the modern design and engineering works. One material that serves as an appropriate substitute of FRP is the Versitex. Versitex Versitex is a new replacement of the common fiberglass-reinforced polyester (FRP) and is manufactured by the U.S. Liner Co. The material is mainly designed to suit the construction of truck bodies and trailers. It is also deployed in construction of refrigerated wall panels, scuff liners and dry freight structures. Versitex is superior to FRP in that it offers a double absorbance protection to that available with the FRP and is lighter and cheaper to use. U.S. Liner Co. manufactures the product in a wide range of assortment to suit the diverse applications with the main variations being the width, height and thickness of the material (Han and Chung, 2011). Versitex has found viable applications in rail, recreational automobile, ships and military equipment manufacturing. The firm manufactures the material from non-woven continuous glass fibers that are embedded with polypropylene and coated to produce a slim, sturdy, and bi-directional constitution. The glass-reinforced thermoplastic characteristics of Versitex material offers worthwhile energy absorption, lessens cracks and punctures in application (Han and Chung, 2011). Advantages of Versitex over FRP Versitex is lighter, cheaper and easier in application compared to FRP Versitex provides higher shock absorbance compared to FRP Has a higher tensile strength of 33.5 KSI, tensile modulus of 1.5 MSI and favorable thermal contraction figures. Versitex is easier to apply and repair and is heat-formable and recyclable. The material contracts and expands almost like aluminum and thus very easy to use Versitex can be molded into complicated forms and/or welded while maintaining its strength The FRP use and technology compared to its use in other developed countries in the world FRP technology application is not restricted to the UK. It has spread to other developed and developing countries particularly in the civil engineering. The ease of application and durability is the reason behind its wide application. The material is also cheaper, stronger than conventional steel, and thus suitable for repair and retrofitting of bridges and other structures. In Europe, it is anticipated to strengthen the spoilt bridges by approximately 5 percent and assist the content to save more than 50 billion every year in repair work. FRP is also deployed in strengthening and retrofitting purposes to enhance both flexural and shear strength of concrete products such as beams and slabs (Harichandran and Baiyasi, 2000). Examples of developed countries that have embraced the FRP technology include America, Canada and Germany. Developing nations such as China and India have also implemented the technology in various applications. The American Concrete Institute (ACI) has deployed the Design and construction of FRP enhanced structures while the Canadian Highway Bridge Design Code (2001) offers clarifications and information concerning FRP materials thus justifying their application in the countries. Reasons for FRP applications Other than lightweight, ease of application and other common characteristics of FRP, it has found application in other countries due to the following reasons: FRP provides suitable adhesive bonding for quality application, control and compatibility of incoming component. FRP provides appropriate ambient characteristics in the hand lay-up method compared to other materials. In resin infusion, FRP also offers significant ambient for curing effect in the applications. Case studies in developed nations FRP Bridge Deck A perfect example of the application of FRP technology is the FRP bridge deck in the U.S. The building was constructed at Lernay Center of Composites Technology and installed at University of Missouri Campus. The bridge passed all the tests including strength, deflection, durability and viability tests. The tests were conducted according to the AASHTO specifications (Han and Chung, 2011). Boston Pedestrian Bridge Boston Botanical Center Project was another successful project of the application of FRP. The main objective of the project was to rejuvenate the region above Central Artery Tunnel, which was not usable due to turnpike (Han and Chung, 2011). China and India Engineers in China and India have also embraced the FRP technology to solve structural challenges in an effective and viable manner. In these countries, the application of FRP technology is restricted to repairing and strengthening of structures (Han and Chung, 2011). NSM (Near Surface Mounting) NSM technology is one form of CFRP application that has been effective for the past 40 years. The technology is very effective in the strengthening of concrete structures including beams. In this method, steel reinforcements are inserted into spaces in concrete frames that have been used in the construction of structures. This method is advantageous compared to steel strengthening because the material used is resistant to corrosion, is light and easier to use compared to use of steel. Another benefit of this technique is that CFRP laminates can be customized to fit the application in various cases. In addition, based on the type of the laminate air voids available, the laminates can be excluded in the deployment (Han and Chung, 2011). Some of the strengthening methods associated with NSM technology include external bonding and near surface bonding. An additional advantage of using the NSM technique in strengthening of beams is that the lowered weight of the fiber makes it flexible to move without necessarily lifting the structure. This makes the application of this technology easier and cheaper. The method is disadvantageous in construction and strengthening works because the CFRP enhanced beams are not as resistant to fire as the steel beams. The beams also require protection because they have high impact sensitivity. An example of NSM application is the construction of the Bristol city car park. The designers employed the NSM technology to strength the Car park at Trent chard Street (Han and Chung, 2011). The technology was not new at that time because it had already been approved in US and Italy. Determinants of FRP application The application of FRP technology is dependent on factors such as climate, aesthetic, maintenance, and cost and time. The benefits and constraints of a particular FRP application technique also determine their application (Teng et al., 2002). All these factors affect the application of FRP materials because these materials are intended to increase the efficiency as well as enhance the viability of construction and repair procedure. When using the FRP materials both the short term and the long-term costs are considered. The costs are evaluated in terms of the costs of the material and the expenses during the application. Although the FRP materials are expensive compared to some traditional materials such as concrete, the installation process and the durability of these materials makes their long-term costs cheaper. The FRP materials are easier to erect and transport and will thus be cheaper to use in the long-term. The climate affects the application of these materials in that there are some places especially the seismic prone areas where certain methods of application of FRP composites would be preferred to others. Retrofitting would be appropriate in such places (Teng et al., 2002). Since the FRP composites can be customized to the required form, aesthetic consideration is of importance. The type of the FRP form used for the strengthening of bridges will be different from that required in the construction of houses. In conclusion, some of the major factors that determine FRP application include the magnitude of the desired strength and the cost; if the project is small and needs special materials, it may be not be cost effective and therefore not viable (Feih and Mouritz, 2012). The environmental condition is also vital. The situation of the environment will determine what to be used. For instance, the use of adhesives is not recommended in conditions of high temperatures. On the other hand, the use of external steel methods may not be suitable in corrosive environments. Conclusion This discussion has outlined the various applications of FRP composites in construction works I both UK and the rest of the world. The applications of FRP composites are always similar in the countries where the technology has been adopted because the advantages and benefits of FRP composites remain the same. Some of the major advantages that make FRP a suitable reinforcement material in major construction works include flexibility, lightweight and ability to be molded into various shapes. FRP is such a unique material such that it is almost impossible to substitute. The only viable substitute for the FRP composite is the Versitex material. The application of FRP material ranges from the construction and reinforcement of bridges and construction of new structures (Han and Chung, 2011). The ability to resist corrosion and the fact that FRP composites do not conduct electricity makes the material very suitable to use in outdoor works. Although FRP has very many advantages and benefits compared to other materials, it has a few drawbacks that make it applications a challenge to designers and engineers. One of the disadvantages is that the material is relatively expensive compared to conservative materials such as girder (Han and Chung, 2011). The durability of the material is not also guaranteed especially in extreme weather conditions. The application of the FRP composites thus requires the consideration of costs, benefits, climate and time. Overall the FRP materials have more benefits than benefits compared to the few drawbacks. Bibliography Feih, S. and Mouritz, A. P. 2012, tensile properties of carbon fibers and carbon fibre-polymer composites in fire, Composites: Part a 43, 765-772, (2012). Han, S. and Chung, D.D. 2011, increasing the through-thickness thermal conductivity of carbon fiber polymer-matrix composite by curing pressure increase and filler incorporation, Composites Science and Technology 71, 1944-1952 Harichandran and Baiyasi, 2000. Repair of Corrosion- Damaged columns using FRP wraps. Michigan.East lansing Jerome DM & Ross CA. 1997. Simulation of the dynamic response of concrete beams externally reinforced withcarbon-fiber reinforced plastic. Comput struct 64(5/6): 1129-53. Teng JG, Chen JF, Smith ST, Lam L. 2002. FRP strengthened RC structures. Chichester: John Wiley and Sons. Read More