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Incremental launch solution demonstrates excellence and innovation

A photo of the Dr Chota Motala interchange

The Dr Chota Motala interchange in Pietermaritzburg, South Africa

30 October 2013 - The upgrade of the Dr Chota Motala interchange in Pietermaritzburg has won the Structural Engineering division award at the 2013 South African Institution of Civil Engineering (SAICE) awards. The awards honour excellence and innovation in the engineering sector and are indicative of top achieving engineering design.

Aurecon, in joint venture with Iliso, fulfilled the role of design engineer on the award-winning R441-million project, which has been widely praised, having already won the 2013 CESA Aon Engineering Excellence award for ‘Best project with a value of over R250-million’; while the Chota Motala Incremental Launch Bridge received a highly-coveted ‘Commendation’ in the ‘Civil Engineering Projects’ category at the 2013 Fulton Awards.

About the Chota Motala Incremental Launch Bridge
The Chota Motala interchange, of which this bridge forms an integral part, straddles the N3 freeway as a major access route to the Pietermaritzburg CBD.

It had been operating at above capacity for quite some time, evidenced by long delays in traffic on the Chota Motala Road (R33). Of even more concern was the dangerous situation created by the backing up of traffic on the off-ramps from the freeway, resulting in through traffic on the N3 suddenly being confronted by stationary traffic in the slow lane. 

After evaluating several interchange upgrade options, authorities settled on a concrete bridge over the N3 which would create a much-needed third layer of traffic at this busy interchange. In addition, the upgrade also included the reconstruction of the existing Dr Chota Motala road bridge as well as the Dorpspruit river bridge; the construction of a new bridge over Du Toit Viljoen road; the widening of the Willowton rail underpass; and the raising of the Retief street rail bridge.

The South African National Road Agency Limited (SANRAL) and the Mzunduzi Municipality appointed Aurecon, in joint venture with Iliso, for the detailed design of the upgraded interchange, with Aurecon responsible for all bridge work.

The main determining factor in the conceptual design for the incremental launch bridge was the client’s requirement that any new bridge over the N3 had to be constructed without disrupting or endangering the heavy traffic on the N3 freeway. It was for this reason that Aurecon proposed the construction of an incrementally launched bridge.

The incrementally launched construction method involves construction of the bridge superstructure section by section on one side of an obstacle and then launching them sequentially into their final position. “The incremental launch technique was considered ideal for this situation,” comments Aurecon bridge engineer, Pierre Van Der Spuy. “With very little risk of disrupting traffic at any stage during construction, it met the client’s requirements in every respect.”

Hennie Niehaus, Aurecon Project Manager, congratulated the project team on this outstanding achievement: “Both the bridge and broader project team are to be commended on their dedication and a job well done. What’s more, this achievement is confirmation of Aurecon’s in-depth experience of designing fit-for-purpose bridge-related structures.”

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