The Help Street bridge had to span 33 metres on post tensioned girders and be designed to support (4) four fully loaded trains parked atop, the height of the bridge was fixed and the height of the underside of the bridge was limited by head height constraints.
The bridge had to be constructed in two halves within the limited once a year five day ‘Christmas’ rail shutdown period, and be ready to operate on sixth day to accept the live operation of trains.
Following extensive analysis to find a solution a design and construct method was achieved incorporating both longitudinal and lateral stressing to laminate the beams together meeting tight construction timeframes and negating the requirement for a central supporting pier and allowed the construction of the six road lanes and footpaths to be constructed underneath.
Works were completed successfully within the tight time frames permitted by the five day ‘Christmas’ rail shut-down.