BG&E’s innovative design modifications to the existing Hay Street Bridge provided additional clearance to reduce the likelihood of collision. Upon completion of this multi-million-dollar project, the bridge now meets the current clearance standards of the transport authority and improves safety for road-users.

BG&E was engaged by Main Roads Western Australia to undertake optioneering work and concept designs that led to detailed design and documentation for the modifications to Bridge No. 0923 on Hay Street over the north and southbound carriageways of the Mitchell Freeway and the southbound entry ramp onto the Freeway.

The superstructure of Bridge No. 0923 consists of 11-cell reinforced concrete box girders. The bridge is nominally 58 metres long with three continuous spans. The superstructure is supported on four reinforced concrete pier columns and walled abutments.

Our highly experienced team designed an out- of-the box solution to raise the height of the bridge by removing three-cells of a 21 metre middle span of the continuous bridge and adding a bridge protection beam.

BG&E designed the removal of the section of the middle span of the continuous bridge to work with the grade of the Freeway below and achieve an increased vertical clearance with minimal impact to the Freeway below and road above.

The removal of the three northern cells from Span Two of the existing bridge resulted in compatibility effects within the other spans from changing a continuous bridge to simply supported for this section of the superstructure. These issues were addressed with detailed design of post-tensioned strengthening inside the cells.

The detailed design of a bridge protection beam at the northern edge of Span Two made use of the existing pier columns and pier diaphragms, with reuse of the stone feature edge parapet also incorporated.