Construction of PCT Girder Bridge Using an Overhead Movable Scaffolding System (MSS)

Norwegian specialist, NRS AS, had been appointed by the contractor of Busan City, SK Construction Co. Ltd. and Kumho Industrial Co. Ltd., to undertake the design and supply of an Overhead Movable Scaffolding System (MSS) for the construction of the Busan-Yongdo bridge in Korea. The construction began at Pier P4 and end just beginning of the Main bridge at Pier YP1, total of 31 spans. The roadway bridge is a single viaduct, Pre-stressed Composite Truss (PCT) girder bridge. The PCT girder is composed of a PC slab lower deck, a RC slab upper deck and steel diagonals. For the light self-weight and relatively strong bending rigidity, the span length varies from 49.232–80.000 m with the average span weight of 17.0 t/m. There are eleven types of different pier head. The 2232 m long bridge is cast in the MSS. The 175 m MSS is mounted on the piers on each ends, cast the superstructure and moved toward the middle. The scope of the NRS AS work includes the design, steel fabrication, and supply of ancillary equipment for the MSS. This paper presents several design challenges due to site constraints and the bridge structures itself. These challenges include high impact loads on the MSS due to adverse wind load anticipated while working nearby the harbor and heavily traffics in the Busan City with limited clearance, special considerations to ensure efficient installation, bridge concreting and launching of the MSS in the sharp curve.