With its 1,100m central span, the 3,100m Russky Island Bridge crosses the Eastern Bosphorus to link the far east port of Vladivostok with Russky Island. Russian contractor SK MOST is aiming for a record-breaking construction period of just 43 months so that the bridge’s four-lane road is open in time for the Asia-Pacific Economic Cooperation summit at the end of 2012. Project cost is €360m.
For the construction of the 320m-high pylon, the contractor is using self-climbing formwork (SCF) supplied by Harsco Infrastructure. The formwork provides a fully enclosed temporary working environment that protects against extreme weather conditions during construction of the pylon and its 70m tall approach piers, which together form part of the record-breaking Russky Island Bridge at Vladivostok in Russia.
To protect men and materials from the severe climate, the SCF is fully enclosed, with a modular, movable roof. The enclosure ensures risk-free operations, even at extreme heights where wind forces can be exceptional. It also allows the work chamber to be heated so that the concrete can set or be patched, even with external temperatures of minus 35OC.
Harsco designed two climbing units for the tapering and inclined geometry of the pylon to speed up construction and eliminate the need for conversion work.
The base has a ground plan of 7.8m x 13m with a 2m wall thickness, tapering to 7.1m x 7m with a 0.7m wall thickness at the top. Only a single work platform has to be removed from the SCF assembly, which is being done during a pre-scheduled break in construction work. All other adjustments and climbing can be carried out without holding up the site work unnecessarily
The SCF unit provides seven work levels with a total height of 19 m, with the top two used for upstream steelfixing. As both the external and internal working platforms are all full-scale, steelfixing can proceed immediately after concrete pouring, saving time and improving safety. On the next two levels, work is carried out on the formwork, and the concrete surface can be heated from here if necessary.
The three trailing platforms round off the rigid, steel-frame climbing pier production unit. These platforms allow the concrete to be protected from the weather for two complete cycles after pouring, and again, heated if necessary. The result is that the concrete can be protected from the weather for almost three whole weeks after pouring, with any patching work carried out in a heated environment.
To accommodate the tight construction schedule, Harsco designed the system to allow adjustments to the self-climbing formwork, and the 72 climbing cycles of 4.5m to be performed quickly. Rigid separation between the steelfixing levels and the shuttering and climbing operations means that once the steelfixing is completed, the formwork can be retracted and cleaned before the climbing shoes are fitted and the climbing rails raised and tied for the next pouring cycle. This allows the SCF platforms to be raised immediately after completion of the steelfixing and the formwork to be moved into its new position ready for the next pour. Once pouring is complete, the steelfixing for the next cycle can begin.
The high load-bearing capacity of the SCF brackets (150 kN vertically and 100 kN horizontally) is crucial to this project, Harsco said. The pylon’s special geometry and continuous tapering mean that only six of the 22 brackets employed actually climb vertically, with the others climbing at transverse and often changing angles of up to 5% from the vertical. Despite its high load-bearing capacity, each SCF bracket requires just a single tie, with installation of the tie cones being a simple task. The cones only need to be positioned at the correct horizontal intervals, and unlike pairs of cones, they do not need to be set at a precisely measured angle. There is therefore no need for elaborate realignment of the bracket to accommodate changes of angle or inaccuracies when setting-up the formwork.
Harsco is providing a formwork foreman and a number of technicians to support the project and ensure that the planned work processes are followed on site.