As part of their continuous maintenance plan, Dampier Salt Ltd planned to replace the existing wet salt dump bridge main steel deck at the Port Hedland site as it was failing due to fatigue loads. The design of the replacement bridge deck for the wet salt dump bridge required fitting into the main existing structure. The sub-structure was still in adequate condition with only the bolted splice connections of the main beams requiring replacement as they were failing due to fatigue loads.
We completed the structural design and documentation for fabrication of bridge deck replacement and main beams welded connections, as well as fatigue assessment of the main deck welded structure, preliminary lift study of main welded frames and on site consultancy during construction and installation.
We faced issues of short timeframe for installation, requiring minimisation of site work, non-flexible geometric constraints, a fatigue governed design and limited crane access.
We managed to overcome this by having off site prefabrication to reduce amount of site welding, purpose fabricated welded beams and a detailed 3D structural FEA under moving loads.
The real key was the value engineering of having the presence of McDowall Affleck’s design engineer on site during the critical stages of installation. Also, the design of the main deck in two large welded frames, fabricated in developing markets and the design of adjustable interfaces to minimise installation risks.