Design of Pylon Cofferdams for Navigational Channel Bridges of Pingtan Straits Rail-cum-Road Bridge

The Pingtan Straits Rail-cum-Road Bridge consists of three cable-stayed bridges crossing navigation channels. The six pylon piers of the three bridges are mounted on dumbbell-shaped pile caps supported by pile foundations. The pile cape of pier N04 of Yuanhong Navigational Channel Bridge measures 81.0 m by 33.0 m, 9.9 m in depth, consuming 18 104 m3 of concrete. To cut down costs, the anti-collision enclosures were employed as the walls of the cofferdam during the construction of the pile caps. Based on which, base plates, tie trusses, partitions and inner bracings were added to form double-wall steel box cofferdams. An individual cofferdam measures 96.8 m (total length, including anti-collision beams) by 37.32 m (width) and 16.6 m in height, which has a draft of 12.88 m and wave resistance of 20 000 kN. The tie truss region of the dumbbell-shaped cofferdam did not require base sealing. The cofferdam was divided into zones to facilitate water pumping, and the pile cap was constructed zone by zone. The construction from hoisting and launching of cofferdam and water pumping to the completion of pile cap fell into 8 control stages. The loading conditions of the cofferdams, base sealing concreting and the pile cap concreting were simulated and analyzed by MIDAS Civil and MIDAS FEA. The results of computation indicated that the stresses in different components of the cofferdams and completed pile caps could meet the code requirements, and the design scheme was feasible. © 2021, Journal Press, China Railway Bridge Science Research Institute, Ltd. All right reserved.