A fast-track building operation combining prestressed hollow-core concrete panel flooring with a light-weight steel frame structure enabled contractors to erect a three-storey, 90-room barracks building for the Botswana Defence Force in barely 20 weeks. It was the first time in that country that a light steel-framed structure had been built incorporating solid concrete flooring – and the project was completed in record time.
For contractor Zangwana Construction (Botswana), the brief from the Botswana Defence Force was straightforward:
design and build a high quality, compact and cost-effective structure in record time without compromising on safety and quality.
Two separate building systems, both recognized for their fast-track qualities, were mated together to meet the challenge.
Echo Prestress hollow-core flooring slabs, manufactured by Echo’s sister company Fastfloor in Botswana.
Polisteel light-weight steel frame construction, employed by Zangwana under licence from the developers, Kotgove Investments South Africa.
“Normally, a light-weight material is used for floors where light-weight support structures are used. But because of sound-transmission, this formula was obviously not suitable in a communal housing development,” says Echo Prestress’s Mike Hull, engineer on the project. “The problem was simply overcome by using the Echo concrete slabs for the upper flooring levels of the building.”
The 4 000m² barracks building is constructed of load-bearing masonry at ground floor level, with the steel frame clad with light-weight concrete. Before construction got under way, the load-bearing capacity of the steel structure was tested at the University of Pretoria and found to be adequate to support the weight of the hollow-core slabs. Hull says the prestressed floors are 30% lighter than a conventional solid slab.
Pieter Kotze, Kotgove Investments CEO, says the combined Polisteel/prestressed concrete panel formula has a multitude of applications, from low-cost housing to commercial, industrial and institutional buildings.
“Its major benefit is a fast, well-engineered and cost-effective construction system that delivers a high-quality product comparable to any conventional system.”