The third Nanjing Chianjing Bridge, the Donghai Bridge, the Hangzhou Bridge and the Runyang Bridge, all recently completed, are among more than thirty suspension bridges with spans in excess of 400m (1,310ft). The Sutong Bridge project is acknowledged as being by far the most challenging of its kind yet undertaken.
The Sutong Bridge extends 32.4 kilometres (20.25 miles) across the wide lower reaches of the Yangtze River between the city of Suzhou (Changshu) and the industrial hub of Nantong City in eastern Jiangsu Province. It has six lanes on a 34m (113ft) wide deck. The bridge project comprises three sections – the road connecting with the northern bank, the river crossing section and the section connecting with the southern bank.
Alone, it consumes 140,000 cu m (5m cu ft) of concrete, 250,000t of rolled steel, 3.2m cu m of earth fill, and has a total project cost of RMB 6.45bn ($800m).
Most impressive of all is the length of the bridge’s central span – at 1,088m (3,570ft), it will be one of the largest in the world. Two massive concrete towers will support the suspension cables and the bridge deck.
Construction of this, China’s first metallic cable-stayed bridge, began in 2003 and demanded the development of special lifting, concrete pouring and pile driving machinery. The largest machinery investment was in the acquisition of two specially-designed
MD 3600 Tower Cranes by Potain, one working on each of the two towers.
The MD 3600s are based on the two giant MD 2200s that were sold in 1998 for use on the Three Gorges Hydro Electric project, now nearing completion, as well as MD 1800s and MD 2200s currently building the Longtan Dam in Ganglia Province (see Cranes Today, September 2004). Although designed with a capacity of 160t, on this project the two MD 3600s have been equipped with two winches
of 80t (88 US tons) and 20t (22 US tons) capacity, each rigged to a different hook. For the job, the cranes were equipped
with 50m (164ft) jibs. This yields lifting capacities of 30t at 48m (32.7 US tons at 159ft) radius and 80t at 28m (88 US tons at 91ft) radius. The smaller (and faster) hook is used to raise concrete forms. The heavier hook lifts cable stays and steel boxes. Maximum hook height is 306m (1,005ft).
The cranes were specially modified by Potain to allow them to withstand high wind speeds. Maximum out-of-service wind speeds are
220 kph (137.5 mph).