The use of Fibre Reinforced Polymer (FRP) sheets to strengthen the steel structures has become an attractive option which may ensure confident retrofitting of existing steel structures. Conventional strengthening techniques for huge steel structures consist of welding additional elements like steel plates or channels to existing structure. In such techniques, the dead load of that enlarged section becomes larger which may result in its ineffectiveness and the added steel plates are also susceptible to corrosion. On the contrary, use of FRPs in strengthening steel structure becomes advantageous due to high strength-to-weight ratio, ease of their drilling and anchoring to existing steel structure and high resistance against corrosion and chemical attacks. In recent years, use of Glass, Aramid and Carbon fibre sheets has become more popular for retrofitting works of R.C.C structures. Therefore it has become a topic of interest for many researchers to examine the effect of FRP sheets in the field of steel retrofitting works.
In this paper an attempt has been made to study flexural behaviour of steel I-beam using basalt fibre sheets and carbon fibre sheets. The results obtained from experimental work have indicated improvement in flexural strength of FRP bonded beams. The comparative results of flexural strength of I-beams bonded with Basalt fibre sheets and carbon fibre sheets are discussed here. Also, the paper includes the finite element modelling of control beam (beam without bonding any FRP material) and FRP sheet bonded beam from ANSYS v.13 software.
IntroductionFRP sheets are formed by embedding continuous fibres in a polymeric resin matrix which binds the fibres together. Common fibres used in FRP sheet include carbon, glass, aramid fibres, while common resins are epoxy, polyester, and vinyl ester resins. The most widely used FRP composites are glass fiber-reinforced polymer (GFRP) composites and carbon fiber-reinforced polymer (CFRP) composites. While use of aramid fiber reinforced polymer (AFRP) composites and basalt fiber-reinforced polymer (BFRP) composites is found to be rarely done.
Conventional strengthening techniques for huge steel structures rely on enlarging the original steel section by welding additional elements such as steel plates or channels. The dead load of the enlarged section becomes larger which may result in a reduction in its effectiveness and the added steel plates become susceptible to corrosion in case strengthened beams are placed in corrosive environment. Also these techniques require heavy lifting equipment during the erection process. Due to these reasons considerable amount of research has been directed to the use of FRP materials for strengthening and retrofitting of steel structures. The main reason of favouring the FRP materials over their conventional counterparts is due to the cost savings resulting from decreasing the project duration, reducing the labour costs, minimizing the equipment demand and avoiding the long durations of traffic diverts in some cases such as steel bridges.
In the past two decades, Fiber Reinforced Polymer (FRP) sheets had been extensively used to rehabilitate concrete structures. This has allowed increase in the strength and ductility of these structures while benefiting the advantages such as high strength-to-weight ratio, ease of their drilling and anchoring to an existing steel structure, high resistance against corrosion and chemical attacks. Another significant advantage of FRP, which applies only to FRP laminates formed via the wet lay-up process, is the ability of such FRP laminates to follow curved and irregular surfaces of a structure which is difficult to be achieved using steel plates. The combination of adhesive bonding with shape flexibility makes bonded wet lay-up FRP laminates an attractive strengthening method in a number of applications. Needless to say, steel plates can also be adhesively bonded but bonding is less attractive for steel plates due to their heavy weight and inflexibility in shape. These uses of FRP sheets to upgrade the resistance of steel structures have recently been studied. The importance to rehabilitate ageing and deteriorated existing steel structures has motivated researchers to develop simple and efficient rehabilitation techniques.
Taking into account the various benefits of using FRPs in strengthening process of structures, it has become essential to study the flexural behaviour of structural members, especially of steel structures, by making use of FRPs. In the present paper, study of flexural behaviour of a rolled steel I-beam has been made by bonding basalt fibre and carbon fibre sheets on tension and compression flanges under four point bending test. The results indicate that the flexural strength of the steel beam increases after bonding with fiber sheets. Also the paper includes finite element modelling of control beam and beam bonded with FRPs in ANSYS (v.13.0) software.
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