Thursday, 13 March 2014

Aluminium tops new Durban tower

Local aluminium manufacturer Alpull has been awarded the contract to manufacture the cowl for the new
Millennium Tower in Durban. The cowl stands on top of a 35 m high concrete structure that houses the port
control. It will be mounted on top of a steel carousel that allows it to rotate in tune with the changing wind
direction, while a central spire will indicate the height of the tide.
The cowl will be manufactured using the high-strength-to-weight ratio Amplibeam structural wall manufactured
using the firm's Ampliform process at its factory in Maritzburg. The Ampliform process involves the slotting and
stretching of an aluminium extrusion to create an expanded aluminium product. The beams make efficient use
of the attributes of aluminium by ensuring that the volume or mass of the metal is placed where it can do the
most work.
The cowl tower is 35 m high, with a base diameter of 14 m, and is fashioned from a truncated cone. Vertical
columns are manufactured using the structural wall type ALB 475, the largest and strongest of the Amplibeam
family. This type is a relative newcomer to the range of structural members and its introduction has opened
many doors for the Ampliform design team. The purlin rings will be manufactured using the structural wall types
ALB 365 and ALB 200, depending on the loading requirements. In total, 12 t of aluminium will be used. When
compared to steel, in volume, the amount of steel would be in the region of 36 t, thus making a notable
difference when designing foundations.
Colourful bands of sheet metal and extrusions will be skirted around the outside of the structure to add
character, and the lower portion will be covered in a mesh skin for aesthetic effect. Amplimesh type 102
manufactured by the firm using the same slot-and-stretch method will be used for this purpose, while strobe
lights will be fitted to enhance night-time viewing.
The wind vane, which points out the direction of the wind, will be a welded aluminium fabrication and standard
aluminium section will be used for this feature.
The Bluff area of Durban is considered to be the most corrosive area in South Africa, hence aluminium is the
most suitable metal. Mill- finished aluminium will be used in the construction with some brackets and all the bolts
being manufactured from 316 stainless steel. The oxidation characteristics of aluminium will ensure the structure
has a long and maintenance-free lifespan. The structural design was carried out by Vawda Thornton Consulting
Engineers, of Durban, and the erection will be carried out by Protekon Construction.
The 75 m Millennium Tower will be erected above Durban's Bluff at the cost of some R7-million.3/13/2014 Engineering News - Aluminium tops newDurban tower

Durban has a signal station on the Bluff, which is used to display visual signals to inform ships whether they may
enter or leave port.
This structure, which was built in 1955, is a simple cylindrical tower, but nevertheless has a significant presence
on the Bluff skyline.
At present, the port control function is carried out from the Durmarine building on the T-jetty in the middle of the
However, the acquisition of a sophisticated radar-based vessel-tracking system demanded more space than
was available in the port control facility. The former Portnet decided to incorporate the old signal station and port
control in a new larger structure on the Bluff, at the location of the old signal station.
Apart from fulfilling a functional role, the tower will become the weather centre for the city of Durban, displaying
wind direction and tide.