Sutong
The Sutong Bridge in Nantong has a main span of 1,088m, and crosses the Yangtze River about 100km inland from Shanghai. DLT won the sub-contract to design and supply the deck erection gantries for main contractor 2nd Navigation Engineering Bureau.
The plan is for the steel orthotropic deck for the bridge to be fabricated offsite, and delivered to the bridge site by barge in 84 16m-long segments weighing up to 450t each. The delivery barges will then be moored in the river below the bridge, and the deck segments lifted to final height, and aligned with the previously erected deck segment ready for welding by eight purpose-made deck erection gantries.
The hydraulic and electrical components for the gantries will be manufactured in Europe and shipped to China, where they will be assembled onto fabricated steel frames made in China. Deck segment erection starts in August 2006, and is due to for completion in June 2007.
The gantries will work in pairs to lift and align the deck units. Each gantry has one 290t capacity DL-S290 strand jack to lift the deck unit, and a system of secondary hydraulic rams to adjust its final plan position and slope so that it can be accurately fitted to the previous deck segment – to within a tolerance of just +/- 1mm – for welding.
The hydraulic systems on each pair of gantries are monitored and controlled by a single operator using the DL-P40 computer control system, which has been developed by DLT for the synchronised control of up to 40 strand jacks or climbing jacks from a single computer screen.
David Dyer managing director of DLT, told Cranes Today: “The user interface was designed by our own operators to give a clean and simple output of the important information. For example, all jack loads are shown graphically as percentages of expected loads, so that when all jacks are working to the expected load the operator sees a straight line of load arrows.”
The DL-P40 system uses the CANbus communication protocol between the control computer and the jacks and power packs, each of which has its own CAN node fitted. CANbus was originally developed by Bosch for use in Mercedes cars, but is rapidly becoming the industry standard for the control of hydraulic systems.
DLT previously lowered a 3,050t steel cofferdam on the Sutong bridge project, using 16 DL-S418 strand jacks monitored and controlled by the same DL-P40 computer control system that will be fitted to the deck erection gantries.
The company has also used the DL-P40 system to synchronise the operation of up to 16 strand jacks on loads up to 3,000t, and it is currently being used on the Bishops Bridge replacement project at Paddington station in the UK, where it is synchronising the operation of eight DL-C450 climbing jacks, and four DL-S418 strand jacks used in the complex launching of a new 2,500t composite bridge deck.
ChaoTianMen
The ChaoTianMen Bridge crosses the Yangtze River in the city of Chongqin in South West China. It has a tied arch main span of 552m with continuous side spans of 190m, and has been designed to resemble the Sydney Harbour Bridge (completed by Dorman Long & Co in 1932).
DLT is acting as consultant to main contractor 2nd Navigation engineering Bureau, and is responsible for developing and detailing the construction method to be used.
The ChaoTianMen Bridge is being constructed as cantilevers out from each end, with temporary stay cables to support the cantilevers. Specially designed gantries will be used to ‘walk’ the steel truss cantilevers, and erect the steel members.
At critical stages in the erection process the two cantilevers will be adjusted for line and level using a combination of 16 DL-S418 strand jacks (418t capacity each) at the ends of the back spans and a series of lateral movement jacks at the tow main piers. In order to align the two halves of the bridge to make the connection in the middle of the span we will be hydraulically tilting and steering two steel structures weighing 20,000t each.
Shibanpo
The Shibanpo Bridge also crosses the Yantzee River in Chongqing, and has been designed by TYLin as a multi-span in-situ concrete box girder bridge with a main span of 330m. The central 108m of the main span has been designed as a steel box to save weight.
The 1,325t, 103m long steel box and two 100t 2.5m long steel transition pieces that connect to the concrete deck at either end of the steel section will be fabricated offsite and transported to the site on barges, where they will be lifted and aligned using strand jacks.
DLT has been awarded the sub-contract to design the lifting arrangement, and erect the main span, for main contractor Chongqing Bridge and Engineering Company.
The lifting arrangement re-uses the existing travelling form frames used to cast the concrete deck, and to supply and operate the strand jack systems required.
To carry out the main lift, DLT is using four pairs of DL-S418 strand jacks (a pair of jack in each corner) – eight jacks in all, monitored and controlled by a single operator using the DL-P40 computer control system.
The lift is due to take place in May 2006.
The Shibanpo Bridge is a cast in-situ balanced cantilever bridge, with the exception of the central steel span. The self-launching formwork frames used to construct the concrete deck will all have completed their work by the time of the steel deck lift, so DLT has designed a scheme to use them as the temporary jacking frames to support our DL-S418 strand jacks to avoid having to make new jacking frames.
