40207_46 - CONSTRUCTION Ever J. Barber0 46 4 . INTRODUCTION...

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CONSTRUCTION 46 Ever J. Barber0 46.1 INTRODUCTION Composite materials are used by the construc- tion industry to replace or complement conventional materials such as steel and con- crete. The main reasons for the use of composite materials are corrosion resistance, electromagnetic transparency and weight sav- ings. Frequently, structural engineers take advantage of more than one salient feature of composites to formulate a design that is com- petitive with an alternate design based on conventional materials. Corrosion resistance is the most important advantage of composites with respect to steel for construction applications. The selection of a composite material usually begins with the selection of a resin that is capable of resisting the attack of a corrosive substance. The corro- sive agent can be anything from spring water to sulfuric acid. Most composite manufactur- ers provide corrosion resistance guides for their products. For example, a table listing the maximum operating temperature of isoph- thalic polyester and vinylester resins as a function of the chemical type and concentra- tion is given by TUFSPAN Technical Data and Design Guide (1991). Chemical resistance of common resins used in pultrusion to various chemical and concentrations as function of operating temperature is given by Pletcher (1991). Fibergrate (1992) supplies a Chemical Resistance Guide for their molded fiberglass Handbook of Composites. Edited by S.T. Peters. Published in 1998 by Chapman & Hall, London. ISBN 0 412 54020 7 and pultruded products listing concentration, operating temperature, and frequency of exposure for a variety of chemicals. Most fiber reinforcements are usually corrosion resistant. Unlike metals, composites do not produce interference with electromagnetic radiation. The resin system can be selected to obtain very low loss factors, but standard resin systems are adequate for most structural applications. Buildings for electromagnetic interference (EMI) testing must be non-magnetic to avoid attenuation and interference with the phenom- enon that is being measured. All computer equipment, for example, must be tested in an EM1 facility. Imaging equipment such as nuclear magnetic resonance (NMR) in hospi- tals must be mounted in a magnetically free environment. An electromagnetically trans- parent cover for communications equipment allows for the use of less-expensive, non-envi- ronmentally protected electronic hardware and reduced maintenance costs. Antennae structures that do not interfere with the signals being relayed or received by the antennae increase the efficiency of the system. While weight saving is the main driving force behind the application of composites in aerospace, it is not so critical in construction projects. However, reduction of structural weight can be exploited as a secondary advan- tage to help offset the higher cost of composites as compared to conventional materials. Lightweight structures require less foundation and supporting structure. In the case of bridges, a noncorrosive bridge deck
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This note was uploaded on 03/16/2010 for the course MECHANICAL ME765401 taught by Professor Prof.sulis during the Spring '10 term at Institut Teknologi Bandung.

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40207_46 - CONSTRUCTION Ever J. Barber0 46 4 . INTRODUCTION...

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