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INDEPENDENT ANALYSIS OF THE STERKSPRUIT VIADUCT BRIDGES ON THE N3

CLIENT: BVi CONSULTING ENGINEERS (PTY) LTD CONSULTING ENGINEER: MOWANA ENGINEERS (PTY) LTD

BVi Consulting Engineers (Pty) Ltd was appointed by the South African National Roads Agency SOC Limited (SANRAL) to provide consulting engineering services for the detailed design and construction monitoring of the realignment of National Route 3, Section 2 from Key Ridge (km 2.8) to Hammarsdale (km 8.1) in KwaZulu Natal. This included two new Viaducts, each with separate southbound and northbound carriageways. Mowana Engineers were approached by BVi to perform an independent analysis of the two viaducts, together with other specialised structural engineering services, as part of their internal design review process. 

The two bridges of Viaduct 1 each consist of 9 spans with a total length of 364m.   The 23.2m wide continuous post-tensioned concrete box decks will receive diagonal structural steel props at 2.8m intervals to support the long deck cantilevers.    The construction methodology for Viaduct 1 will utilise the Incremental Launching Method (ILM). Click here to view a video illustration of the ILM.

The two Viaduct 2 bridges will each consist of 5 spans with a total length of 178m.   The 23.2m wide decks will consist of 4 continuous post-tensioned concrete spines each.   These bridges will be constructed in-situ, starting with the central span.

Mowana Engineers, who are proficient in RM Bridge, conducted independent analyses of the viaducts to confirm the structural behaviour and results observed from the SOFiSTiK models, prepared by the BVi team.  In addition to the analyses, the Mowana team provided expert input on several complex fields in bridge engineering. This included the design and construction of incrementally launched bridges, the seismic analysis of structures, post-tensioning systems, shear-lag and transverse membrane behaviour of wide bridge decks and structural steel and connection design.

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