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Monorail Bridges, The
Thesen Island, Knysna, Western Cape

Michael P (Mike) LOUW: Design Architect
Michael P (Mike) LOUW: Project Architect



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34°02'55.60" S 23°02'57.92" E Alt: 5m

The Monorail bridge is situated on Thesen Islands in Knysna. This is on the site of the former Thesen Sawmill, which has been developed into a large residential estate with a smaller commercial core. The original island was divided into nineteen smaller islands, which necessitated the construction of various bridges.

A number of the old industrial structures have been retained for adaptive re-use and the Monorail is one of these. The structure was used as a gantry to transport timber to and from the kilns and is approximately 25 years old.

Most of the existing structural framework (which consists mainly of large I section portal frames) was kept in place and has been restored. The Monorail was subsequently bisected by two of the new canals that separate the commercial core from the residential areas, which is part of the reason why it was retained - when the urban planning was being done, the pedestrian routes were planned to coincide with the Monorail's location with the idea of integrating the structure with a bridge.

Three of the existing portals were moved to the western side of the canals and two bridges were designed to be suspended from the structure. The position of the canals necessitated two separate bridges with spans of 46 metres each. The brief was to keep the structure of the bridges at thin as possible while allowing enough clearance underneath to allow small boats through.

Each bridge consists of two steel channels with angle ironed horizontal cross bracing in between and the handrail, which is a hollow tubular section, also serves as a structural element. The bridge is supported on a concrete base at each end and the span is suspended from the existing Monorail by steel rods. A timber deck was inserted between the steel channels and all the electrical conduits are hidden within this structure.

(Mike Louw - April 2013)