SRG Global was commissioned to erect a mobile stage hanger scaffold for the purposes of coating refurbishment on the Waikato Span River Bridge in Taupo, New Zealand.
The scaffold was an engineered design mobile stage hanger, with overall dimensions of 21 metres x 6.5 metres, weighing 13 Tonne and with a live load of 600 kg’s. To execute the work the stage was required to travel to one end of the 120 metre long bridge and back and was constructed initially on a decked scaffold at the northern abutment before being moved over water.
The stage scaffold system components were mixed; using RMD slim solders and push pull props for the mobile set up and droppers, connecting to a total of 42 Layher 7 metre Trusses. All of the transoms, putlogs, plan and dogleg bracing was a mixture of conventional tube and clip and Layher system.
As a requirement for resource consent and protecting the waterway below, the deck was also lined with a textile filter cloth and plywood with 20 mm drilled holes every 200 mm to enable cleaning water to run through onto the filter cloth while, containing abrasive material within the scaffold. The stage was then completely shrink-wrapped to prevent dust and paint contaminating the local environment.
I beams were temporarily engineered, positioned and continually leapfrogged on the Eastern side of the bridge to enable the stage hanger to track safely during movement. Movement consisted of a team of five (in radio contact) progressively lever hoisting hangers in controlled 6.5 metre staged moves across the bridge. Once in position hangers were chocked and lever hoist secured while painting refurbishment took place. On-going daily inspection was completed throughout the project to ensure vibration from traffic did not affect the integrity of the scaffold stage.
The bridge waterway is also home to the Huka Jetboat, which regularly performing high speed 360 degree turns directly underneath the bridge, so height clearances were also continually monitored.