Fast-track building combining prestressed hollow-core concrete panel flooring with a lightweight steel frame structure enabled contractors to erect a three-storey, 90-room barracks building for the Botswana Defence Force in barely 20 weeks. This project marked a first for the use of these twin technologies in Botswana – and it was completed in record time.
For contractor Zangwana Construction (Botswana), the brief from the Botswana Defence Force was to design and build a high quality, compact and cost-effective structure fast, without compromising on safety or quality.
Two separate building systems, both recognised for their fast-track attributes, were used together to meet the challenge: Echo Prestress hollow-core flooring slabs, manufactured by Echo’s sister company Fastfloor in Botswana; and Polisteel lightweight steel frame construction, which was used by Zangwana under licence from the developers, Kotgove Investments South Africa.
Mike Hull, Echo Prestress’s engineer on the project, says, “Normally, where lightweight support structures are used, a lightweight material is used for the floors. But because of sound transmission, this formula was not suitable in a communal housing development like the barracks. The problem was simply overcome by using the Echo concrete slabs for the upper flooring levels of the building.”
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. According to Hull, the prestressed floors are 30% lighter than a conventional solid slab. The 4 000m² barracks building is constructed of load-bearing masonry at ground floor level, with the steel frame clad with lightweight concrete and the prestressed floors used for the upper levels.
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.
“The major benefit is that it is a fast, well engineered and cost-effective construction system that delivers a high quality product comparable to any conventional system.”