Instant bridges in Hammarsdale

MODERN engineering has made it possible for a bridge to be erected across both carriageways over a busy highway in four days.

Recently, traffic on the N3 from Durban to Pietermaritzburg was diverted for two consecutive weekends to make it possible for a new bridge to be erected at Hammarsdale.

The development of the Keystone Park Light Industrial, Warehousing and Logistics Precinct at Hammarsdale has increased the volume of traffic, especially heavy vehicles, using the intersection of the N3 and MR 385.

The South African National Roads Agency SOC Ltd (Sanral) decided that the interchange must be upgraded from a simple diamond interchange, to a new semi-parclo (partial clover leaf) free-flow interchange to prevent a back-up of trucks onto the busy N3.

Ian Jackson, resident engineer at Hatch consulting engineers, said in order to minimise delays, precast beams were used.

The beams were cast in a specialised casting yard approximately five kilometres away from the construction site and were transported from the casting yard to site with special low-bed vehicles.

As each beam weights 37 tons, a large substantial crane was used to lift and place each beam in position.

It took two days to position 23 beams per deck. Owing to the positioning of the crane to lift the beams and the potential danger to traffic, each carriageway was closed during the lifting and placing operation. — Supplied.