Experimental investigations on strengthening of rc beams by external prestressing

Experimental investigations have been carried out on five specimens, out of which three were of single-draped tendon profile and two were of straight tendon profile. Rectangular RC beams of section size 150 mm X 275 mm with 4 m length were used for investigation. Crack was induced in RC beams to a limit in which strain in reinforcing steel was around 85 % of the yield strain by monotonically increased static two-point load at flexural zone. Strengthening by external prestressing was done while the member was subjected to superimposed dead load of a bridge girder, equivalent to 25 % of the calculated ultimate load of the specimen. Strengthened members were tested by monotonically increased two-point load. Role of the reinforcing steel were observed from electrical strain gauges, which were fixed throughout the length of the beams. It was observed that the ultimate load carrying capacity of strengthened members have increased 48 % and 17 % for single-draped tendon profile and straight tendon profile respectively.