DESIGN OF PRE-STRESSED CONCRETE T-BEAM BRIDGES

The concept of pre-stressed concrete appeared in the year 1888. In this present engineering technology, durable and sustainable bridges play an important role for the socio-economic development of the nation. Owners and designers have long recognized the low initial cost, low maintenance needs and long life expectancy of pre-stressed concrete bridges. This is reflected in the increasing market share of pre-stressed concrete, which has grown from zero in 1950 to more than 55 percent today. This growth continues very rapidly, not only for bridges in the short span range, but also for long spans with excessive length which, here therefore, has been nearly the exclusive domain of structural steel. Many bridge designers are surprised to learn that precast, pre-stressed concrete bridges are usually lower in first cost than all other types of bridges coupled with savings in maintenance, precast bridges offer maximum economy. The precast pre-stressed bridge system has offered two principal advantages: it is economical and it provides minimum downtime for construction. Pre-stressing is the application of an initial load on the structure so as to enable the structure to counteract the stresses arising during its service period. In the present project, the behavior of pre-stressed concrete beams, how they will be stressed, the percentage of elongation, and the pressure applied to make beams pre-stressed will be thoroughly examined. This work presents a practical approach on a major bridge having 299 m span, 36 PSC Beams and 8 RCC Beams. The study focuses on PSC Beams, where the beam post-tensioning values, rate of elongation and behavior can be defined after stressing. The main code followed in this course is IS: 1343 - 2012 entitled Code of Practice for Pre-stressed Concrete. It is published by the Bureau of Indian Standards. Some provisions of Code IS: 456 - 2000 entitled Code of Practice for Structural Concrete are also applicable to Pre-stressed Concrete.