ABSTRACT
The beams were supported on cast-insitu crossheads and precast, prestressed piles. A nominal 35mm asphalt seal was placed over the beams. The posttensioning process is shown in Figure 2.
In 1976, the state road authority was informed that calcium chloride had been used as an additive to the concrete during construction to aid early setting of the concrete. This was common practice for the day but has since been banned (Cook 1976). A detailed inspection of the bridge in 1978 revealed corrosion-related defects on the piles and crossheads but no significant defects were identified on the beams (Hurd 1979). In 1993, an underbridge inspection revealed a crack had instigated along the web of beam #12 within the seventeenth span from the western abutment (Giana 1993; van Grieken 1994). Consequently, the frequency of underbridge inspections were increased and by 2000, some 51 beams showed similar cracking. In some instances the cracks were in excess of 20mm width and some prestressing strands were directly exposed to the elements. Figure 3 shows one of the worst cases of longitudinal web cracking.
