Storage area for raw materials for all production lines at the smelting plant, originally for limestone and coke for making carbide. This is where raw materials were stored and selected, and where the cableway endpoint was located. It is a striking building and a remarkable engineering feat.
10 000- 18 000 tonnes of limestone were stored here before they were transported to the kilns on rubber conveyor belts.
Shell roof storage building. Photo: Harald Hognerud Kraftmuseet
The shell roof is an open, elongated construction in reinforced concrete with a roof supported by pillars. Underneath the concrete floor there are underground passages, and below the roof there are conveyor belts, a footbridge and a cableway line with turning point for the cradle cars. The whole construction, including the structures on the short walls with conveyors, is in reinforced concrete left in view.
The cradle cars travelled along the cableway from the import harbour, through a building on the short wall of the shell roof, to the end of the shell roof where they turned around a wheel and changed direction. Along the way coke was dropped in the northern part of the storage area, and limestone in the southern one. The crushing station and the station for reloading the limestone are located on the southern end of the long roof, while the cableway terminal is found on the northern end.
Cradle cars arriving the shell roof storage. Photo: Kraftmuseet archives
The shell roof construction is a Norwegian invention, developed by engineer Olav Olsen in the years after World War II. At a time when building materials were scarce, this type of construction was advantageous because a large span may rest on very few support points. The roof is only 8 cm thick, reinforced with transversal ribs and beams in reinforced concrete which connect the load-bearing pillars placed at the edges of the barrel roof. There is a large open area below the roof. All functions required for storing and handling the materials are placed along the sides or suspended from the roof, so that the space below the shell roof remains unobstructed.
There is a concrete wall at the southern end of the storage area, with reinforcement placed both lengthwise and crosswise. The main purpose of this wall was not to bear the roof, but to support heaps of limestone.