Caption: Some of the southern elevation columns with hollow-core slabs in the foreground prior to installation.
Written by David Beer on behalf of the Concrete Manufacturers Association
This is Part 1 of a two-part series.
Reserve-5, an attractive 5 500m² distribution warehouse in Brackenfell, Cape Town, has been built with several precast concrete elements supplied by Concrete Manufacturers Association member, Cape Concrete Works. Completed in December 2023, Reserve-5’s precast components comprise columns, hollow-core slabs for walls and flooring, and precast stairs.
This is no ordinary distribution centre. Visually striking and pleasing to the eye, precast concrete has been skilfully deployed as an aesthetic as well as a structural component by architects BLOCK ■PLAN. What’s more, of the 45 precast columns supplied by Cape Concrete, only two were placed inside the building for roof support.
“We were able to create a sense of rhythm across all elevations,” said Gordon Hubbard, managing director of BLOCK ■PLAN. “We did this by placing the main body of the columns outside rather than on the inner side of the walling. This structural rhythm was further enhanced by capping off the walls with eight-metre L-beams. The 300mm upstand width of the beams mirrors the width of the columns and this gives the walls a very uniform concrete coping on all elevations. Moreover, the beams create a horizontal framework which forms a pleasing contrast to the vertical column work.”
The wall columns were cast with vertical slots from top-to-bottom to accommodate the wall slabs and by positioning the body of the columns outside rather than inside the walls, more internal space was generated. Additional space was achieved by restricting the number of internal columns to two.
Cape Concrete installed all the precast concrete elements and Ekcon (Pty) Ltd Consulting Engineers handled the structural engineering.
Construction began with the installation of the columns. Spaced at eight metre intervals across all four elevations, the columns created a framework for the installation of the wall slabs and the roof assembly. Using the Peikko Bolting System, galvanised steel shoes were cast into the bottom of the columns and matching steel bolts were attached to the column footings. The bolts were spliced with the footing reinforcing, a process which required great precision, and to this end, Cape Concrete provided the contractors with templates to ensure that the footing bolts were placed accurately.
Cape Concrete also cast two lifting pins into each column which were neatly grouted once the columns had been installed. The pins enabled a mobile crane to lift the columns off the truck beds and lower them into position over the footing bolts. Once column alignment had been adjusted with spacers, steel nuts were attached to the bolts to lock the columns permanently into position.
Before the hollow-core walling panels were inserted between the columns, a central heavy-duty roofing girder was assembled on the building’s east-west axis. The girder was supported by the two internal columns and two wall columns. Thereafter lighter steel sections were bolted onto the girder and some of the walling columns. Cape Concrete cast steel brackets into these columns to facilitate the attachment of the steel roof sections to them.
The warehouse has a floor-to-roof height of 11m and all the perimeter columns are 11m high. The two internal columns consist of 8.3m concrete columns mounted with 2.7m steel sections. PVC 200mm rain-water downpipes were cast into the two internal columns. This is because the roof falls towards the mid-point and all rain-water drains into the downpipes and then into drainage pipes embedded in the flooring.
Once all the wall panels were in place, Cape Concrete installed the L-beams which were attached at either end with Y16 dowel bars.
Continued in Part 2…
