Award winning
Sentech

Sentech

Guyed masts are one of the most complex non-linear structures that one can encounter as a structural engineer.  Due to the nature of the non-linearity of the cable elements, the solving of the cable forces is a highly iterative procedure.  Appurtenances attached to the mast are generally modelled as applied dead and wind loads in the model, whilst thick feeder cabling can also effect the mast solidity ratio and add significant wind and dead load.

In 2012, the telecoms giant Sentech SOC, embarked on a countrywide network expansion project which included the upgrading of some 180 sites from the existing Analogue transmission to Digital Terrestrial Television (DTT). 

The DTT works package are broken down into two main components:

  1. The design and construction of the core infrastructure for seven new guyed mast greenfield sites, including the construction of the associated new access roads, transmitter buildings, sub surface copper earth mat systems, and satellite dish antenna foundations for 4.5m/2.4m diameter satellite dishes. These seven sites are situated at Burgersfort, Harrismith, Holy Cross, Lady Frere, Cofimvaba, Ngqeleni and Qokama.
  2. The installation and addition of an extra guyed level and Kathrein UHF Antennae (approx. 10m high, 2 000kg in mass) above the existing FM Antennae cantilever section of the mast for some 19 existing mast sites. This work typically included modifications to the existing RC anchor blocks to accept the additional guy ropes as well as the fabrication and installation of a new platform and mast adaptor section.  This component of the DTT work proved to be particularly challenging as new structures had to match the existing with a high degree of precision.

The broadcaster transmitter stations are more often than not located on remote mountain tops or high ridges, in unmanned areas and are only visited on a scheduled maintenance or call-out basis.  Some of the 4-leg “Liebherr” type masts that were considered for this project are in excess of 280m in height. 

The addition of the new transmitter sites will ensure maximum digital terrestrial coverage in the far lying areas of South Africa.

Project Information

Status
Construction Completed
Site Area
2 000 m2
Project Area
2 000 m2
Project Type
Telecommunications
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