Bridges

The pot bearings on ten dual track heavy haul rail bridges over waterways in the Pilbara region of Western Australia were showing premature degradation and required replacement. BG&E Pty Limited was engaged to calculate the abutment and pier bearing design loads to comply with the additional loading required under the AS 5100:2017 Bridge design code.

The main changes resulted from the enhanced requirements for heavy haul rail braking and traction, water flow probabilistic factors in the flood and debris loading, and more explicit fatigue and cycle loading than the previously assumed Miner’s Rule.

The principal objective of this project was to upgrade the bearings to ensure prolonged life of the bridges and continued heavy haul rail operations for its intended design service life of 50 years. A secondary objective was to provide abutment and pier permanent access to assist with bearing replacement operations as well as provide access for future inspections and maintenance.

BG&E also undertook a structural integrity assessment of the ten bridges to assess the impact of the bearing change and addition of platforms on the integrity of existing bridge components, as well as quantify the increased loads from code changes since the bridges were designed.

BG&E also liaised with the bearing manufacturer and contractor to ensure that the bearings could be efficiently replaced within the short shutdown periods. The replacement bearings were of spherical type. A Senior BG&E Bridge Engineer was present on site during the bearing replacement works to expedite the resolution of any unforeseen issues. All bridge bearing replacements to date have been completed before the shutdown ended and without incident.