Two edge beams from a 32 year old segmental post-tensioned concrete bridge were load tested to failure. The failure mode of the two beams differed considerably. The first beam tested failed at a maximum moment of 2730 kNm at a deflection of 105 mm. The maximum moment applied to the second beam was 2090 kNm and this caused a deflection of 54 mm. As the deflection was increased further the applied moment reduced but the beam did not fail until it reached a deflection of 260 mm. Several methods were used to measure the prestressing force in the tendons. The mid-span losses for the two beams were of the order of 10 per cent to 15 per cent, although losses were higher at some of the joints in the second beam tested. This was attributed to corrosion of the tendons at the joints which was more severe than in the first beam. Optical fibre and crack propagation gauges were used to detect the opening of the joints between the segments to determine whether they would be suitable for on-site monitoring. Neither type of gauge gave a reliable indication of joint opening. (A)
Abstract