This 410 m-long railway overhead was damaged by a failure of the underlying soft clays, causing large lateral movements of some support piers. Klohn Crippen Berger was first engaged to perform a structural and geotechnical assessment and submit a repair strategy report. The report included rehabilitation measures to restore the damaged structure to its undamaged condition and listed emergency repair actions that would temporarily strengthen the structure. The temporary repairs included longitudinal restrainers to connect spans at expansion joints and temporary steel support towers and foundations. The steel support towers were constructed from portable Acrow bridge components owned by the Ministry.
Subsequently, conceptual and detailed designs for permanent repairs, along with construction cost estimates, were developed for the damaged portions of the overhead. New steel piles were installed to replace the damaged concrete piles. New pile caps were constructed to support the damaged substructure and transfer loads into the new piles. The existing concrete pier columns and cap beams were strengthened using fibrewrap reinforcing. Structural steel collars were installed at the top of the columns to reinforce the column/cap beam joints. Damaged sidewalk panels and pedestrian railings were also replaced.
- Structural assessment
- Geotechnical investigation and assessment
- Temporary and permanent foundation strengthening design