Civil Engineering March 2021 | Vol 29 No 2

42 March 2021 Civil Engineering • Earth embankments • Bridge abutments • Cut slopes • Steep channels • River banks • Culvert inlets/outlets APPLICATION: UNIQUE PRODUCTS: • Florawall (earth terrace retaining support) • Earthform (natural support for terraces) • Enviro-Wall & RocEnviro-Wall (retaining wall system) Find our branches at www.technicrete.co.za p a v i n g | m i n i n g | m a s o n r y | k e r b s | e r o s i o n p r o t e c t i o n | r e t a i n i n g w a l l s | d r a i n a g e Technicrete is a subsidiary of ISG, a leading supplier of innovative infrastructure products to the construction and mining markets in Southern Africa. The steel deck comprises cantilevering cross beams that are fabricated I-sections; a longitudinal edge beam that is a triangular closed section; and bracing members that are standard angle and T-sections. The end beam houses the bridge wheel assembly and is a box section to resist the loads at the deck tip. The pylon is a fabricated box that has been sculpted to provide strength and stiffness where required. The stay cable anchorages are discretely housed within the top of the pylon with an access panel at the back to allow for stressing and inspection. Challenges and innovations The large size and heavy weight of the bridge created a big challenge in terms of moving and rotating for welding and fabrication. To limit disruption to the V&A, the bridge was assembled on a nearby jetty and then carefully craned onto a barge and towed to its final position. The bridge was then lifted and mounted onto the slewing bearing in an amazing process that took two days and careful co-ordination. A moving bridge project is unique in itself, and for the design team the greatest technical achievement was the combination and integration of mechanical, structural, marine, geotechnical, construction and architectural expertise to create a simple but beautiful structure that moves. The use of a slew bearing was a technical innovation not seen before in Africa and the design team had to undertake detailed research and modelling to vali- date it could be used for a bridge of this type. The creation of this relatively lightweight and slender structure would not have been possible without steelwork, which enabled the integration of architecture and structure to create a bridge that can be recognised as a landmark.