Strengthening of Mithi River Bridge Under N1 Taxiway at Mumbai International AirportDr. Gopal L. Rai, CEO and Managing Director, R&M International Group, Mumbai.
IntroductionStrengthening of RCC structural elements is a common task for maintenance nowadays. For the purpose of strengthening, several materials and methods are available such as sprayed concrete, ferro-cement, steel plate and Fibre Reinforced Polymer (FRP). Sprayed concrete is the oldest materials amongst the group and is the most common method of repairing and strengthening of reinforced concrete structures. Among all of the strengthening materials, steel plate and FRP laminate are the most common and effective materials due to their several advantages.
FRP for civil engineering structures are being increasingly studied in recent years. These materials are being used in the aerospace, automotive and shipbuilding industries for almost two decades. In general, FRP offer excellent resistance to corrosion, good fatigue resistance (with the possible exception of some glass-based FRP), low density, high stiffness and strength, and a very low coefficient of thermal expansion in the fibre orientation. FRP materials as having superior mechanical and physical properties than steel, particularly with respect to tensile and fatigue strength. The FRP is usually considered only for special applications, such as in non-magnetic structures, or for use in aggressive corrosive environments. However, the usage of FRP can be more economical than using steel plates. This is because the material costs in a rehabilitation project rarely exceed 20% of the total cost of the repair. Several FRP systems are now commercially available for the external strengthening of concrete structures. The fibre materials commonly used in these systems include glass, aramid, and carbon.