Stainless Steel Awards 2008

Winner Projects Category

Rebcon Engineering
Project : Cladding of Timeball Tower

This year’s winner of the Stainless Steel Award for best project goes to Rebcon for its awe-inspiring Timeball Tower. The purpose of constructing the Timeball Tower had both a historical and architectural impact on the new Durban Point Development Project. From a historical perspective, in the early 1900s Durban Port had a Timeball Tower that played an important role in advising ships entering port what the time was. The design team on this project wanted to incorporate this historical importance into the structure.

From an architectural perspective the structure symbolises the origin of the public focal point of the Point Waterfront Development, namely the information kiosk, amphitheatre and ablution block. It also provides a link between the various icons within the development. The architectural design was undertaken by Rodney Choromanski of CNN Architects and the structural design was undertaken by Leezane Greyling of Arup Consulting Engineers & Linda Ness of Linda Ness Associates.

The architect’s concept was modelled using wire as a sculpting medium, and the challenge to recreate this filigree effect could only be realised with the use of structural steel. The final constructed product is a visual scaled model of the architects’ original wire frame model.

The structural design offered challenges due to the slenderness of the structure. Analysis of effects of wind loading was undertaken by Arup (UK), and strakes were introduced to accommodate the effects of wind loading
to the upper sections of the structure. The lower section of the structure comprises a compression framework fabricated ex grade 350WA central core tube with grade 350WA fabricated plate compression rings and grade 350WA rectangular hollow section diagonal bracing, all post tensioned by use of 36 diameter grade 316 stainless steel Macalloy tendons, post tensioned by means of hydraulic jacking prior to erection. The top section of the structure comprises of a continuous fabricated tapering box section ex grade 350WA plate. Weld procedures, monitoring, inspections and testing were undertaken by Innovative Inspection Services. All carbon steel was coated with a Denso coating designed for the aggressive environment in Durban.

Application of this coating was undertaken by Pipe Coatings. The holding bolts are ex 36 diameter grade 316 stainless steel, all connection bolts are ex either grade 316 stainless steel or grade 8.8 hot dipped galvanised.

The cladding to the lower and upper portions of the structure is ex grade 316 stainless steel plate perforated to suit the architect’s requirements. The Timeball operation mechanism is manufactured on a pulley drive system driven by a servo motor that is linked to a computer at the base that operates the sequenced movement of the ball. The ball was manufactured ex GRP and painted with a chromed finish.

The “copper bangles” were manufactured ex GRP by AGS Glassfibre. The design of the electrical & lighting to the structure was undertaken by Imvuselelo Consulting and all electrical supply and LED lighting requirements was supplied and installed by Cato Ridge Electrical.

The contract period was originally set for six months, commencement being July 2006 and completion December 2006, however, due to delays in shipping the Macalloy tendons from the UK the project completion date was delayed to April 2007. The project was finished within the client’s budget allocation.