The Nanjing Yangtze River Bridge, the first China-designed bridge to span the country's longest river, is undergoing its fifth overhaul in four years.

The overhaul aims to mend expansion joints, which are cracking, on the southern section of the bridge, which is nearly 40 years old.

Despite yet another repair programme, the bridge will need further work done to it in the coming years.

This current project will focus on the bridge's girders.

"After many years' work, the girders have been ruined and the joints between the girders have seen subsidence and cracks, which is certainly a danger," said Luo Tao, leader of the city's No 9 transportation administration bureau.

The expansion joints on the northern part of the bridge were repaired last year.

According to Luo, the work will be carried out each day between 10 pm and 6 am over a period of 20 days.

Traffic control will be in force, as only half of the bridge's six lanes will be in use during the overhaul, which began on Wednesday.

Last year there were two thorough repair programmes on the bridge to improve the road surface, lights, sculptures and railings.

"All these overhauls, including the present one, are just minor projects that will only affect traffic temporarily," Cui Peide, head of the Nanjing Yangtze River Bridge administration was quoted as saying by local newspaper Modern Express.

According to Cui, cracks in the expansion joints and an uneven road surface would appear again as the main girders have degraded with decades of use.

A survey conducted by the local transport bureau this March found that more than 60,000 vehicles used the bridge every day, a figure that is four times its previously estimated capacity.

While the city boasts three bridges, this crossing, previously a major link between North and South China, was turned into an inner-city transport route last December with a ban on vehicles from outside Nanjing.

But no apparent drop in vehicle numbers has been recorded, according to Luo.

"Too many vehicles using the bridge has distorted its steel and concrete structure and the asphalted road surface has also aged. The whole bridge should have a fundamental overhaul," said Cui.

Built in 1968, the Nanjing Yangtze River Bridge is a double layer structure, with its upper 4,589-metre-long route reserved for highway traffic and its lower 6,772-metre-long span used for trains.

Source: China Daily