REHABILITATION OF R.C. BRIDGE GIRDER

Abstract

The reputation of concrete as a maintenance free and durable material has been seemingly tarnished during last two decades due to rapid rise in deterioration of concrete structures worldwide. Nonetheless, the global trend of deterioration of concrete structure is being manifested in India too and same is likely to get further aggravated in the near future. Take for example, there is unabated increase in number of deteriorating railway and road bridges In the country. Unfornately many of these distressed bridges are only just few years old. The bridges may need rehabilitation due to the distresses arising out of many reason such as improper design, faulty construction, overloading, environmental causes etc. In this dissertation work, two situations requiring strengthening have been envisaged, first of strengthening for original weak concrete beam and second of strengthening for overloading. Also, two different techniqes of rehabilitation i.e. epoxy bonded steel plates and external prestressing have been used. In first technique, the attempt was made to study the behaviour of beams rehabilitated with steel plates of smaller length. And it was found that ultimate strength of bridge girder can be significantly increased by epoxy bonding of steel plates. But if plates of smaller lengths are to be glued then steel plates on the sides are must to prevent premature failure of the girder. The increase in ultimate load was, 2% for pretested beams rehabilitated with plates on the bottom only and 21% for pretested beams rehabilitated with plates on bottom as well as on the sides and 26.5% for untested beams strengthened with plates on the bottom as well as on the sides. Beams rehabilitated with external prestressing showed an improvement of 48% in ultimate load. In all the rehabilitated beams, the deflection's and crackwidth reduced marginaly and were found much below than the permissible range (except for beams rehabilitated with s