West Gate Bridge – Pier 10, 11 & 12

Westgate Bridge: Innovative Scaffolding at Westgate Bridge Pier 10

The Westgate Bridge has a long history with building commencing in 1968. Two years into construction of the bridge, at 11.50 am on 15 October 1970, the 112m (367.5 ft) span between piers 10 and 11 collapsed and fell 50m (164 ft) to the ground and water below. Thirty-five construction workers were killed. A monument has been erected at the base of Pier 10 to the fallen workers. This created a unique environment for the team to work in as they were building around this monument – even with the much advance knowledge, vision and engineering the team now has and the capabilities of the team – they are still aware of the danger and the history of that bridge and ensured at all time safety was of extreme importance to everyone.

The requirements at Piers 10, 11, and 12 were complex and challenging. Pier 10 could not be built in-situ, and the design needed to address these restrictions. The Stilcon Scaffolding team created cutting-edge designs that suited the client’s specific needs. It was designed as a cantilevered spanning scaffold extending from the grillage around Pier 10 and hanging from the protective barriers on the side of the bridge.

To assist with efficiencies on the project, SIS supplied its own cranes and booms, enabling the team to be more self-sufficient during the build. They worked with plant and equipment at high levels such as working out of booms that reach up to 60 or 70 metres high and working closely with 90 tonne cranes to deliver scaffolding and equipment.

Pier 10 had four areas each with different design and work requirements.

Due to the high-risk elements involved working at these heights, SIStook it upon themselves to offer several VOC trainings, also ensuring rescue training was completed by all scaffolders/riggers working on this project.

Pier 10 had four distinct areas, each with a different design and work requirements. Area One involved a 21-metre span off the grillage that covered the spine of the Westgate Bridge using a new Layher system called flex beams. Area Two was a waterfall effect coming from the side of the barriers on the east and west side of the bridge and cascading down towards Area One. Area Three came off the structural stairs and spanned out five metres with a cantilever of eight metre ladder beam. Area Four had to be completed with flex beam drilled into top of Pier 10 and then cantilever out towards the west.

The piers were 42m, 44m and 46m respectively, and each was subjected to high wind forces. As the scaffold was encapsulated, careful measures were implemented to counteract potential buckling of the standards. Ties were installed at each level to reduce the effective standard length for buckling checks.

The use of conventional socket base ties would have impeded the remediation process, therefore an alternative tying solution was adopted. A single self-tapping screw anchor with a threaded bar, tube over and locking nut was utilised. This approach maximised the work area, allowing the client to prepare the wall without any patching required.

Pier 11 required the scaffold to be erected over an existing bomb shelter, which resulted in the inner standards not being grounded. To overcome this issue the scaffold was suspended from the walls at a low level, using in-house developed shear plates. Due to the estuary’s water reaching high up the bank, structural steel was installed at the base, spanning from a large pad foundation to wall plates. All steel detailing was carried out in-house.

For environmental compliance, non-toxic chemical water blast methods were employed to effectively strip the piers’ coatings back to the bare substrate. A comprehensive wastewater management system was implemented by encapsulating the scaffold and creating a bunding around the base to effectively collect and manage wastewater. This water was continuously managed using water pumps that directed it into two 10,000-liter water tanks, emptied 2-3 times a day by a waste collection company.

The team prides itself on the complexity of all these elements and its ability to find solutions, which benefits its clients on each project.