Construction World June 2022

CIVIL ENGINEERING

PRECAST WIND-LOAD COLUMNS BUTRESS LARGE WAREHOUSE

Massive precast concrete wind-load columns in addition to smaller precast columns and precast tilt-up panels have been used to reinforce a warehouse being built on an industrial estate situated in Pomona, Gauteng. Text by David Beer on behalf of the Concrete Manufacturers Association.

The southern elevation and the five wind-load columns.

B oth the columns and the panels were cast on site by precast concrete specialist, Superstruct. Developed by JT Ross, the structure was designed by architects, Empowered Spaces. Sutherland Engineers handled the structural and civil design engineering and Bantry Construction was the main contractor. Construction of what is one of the largest warehouses in the country started in August 2021 and the first of this three phase project was completed in the first half of 2022. According to Donnie Smith Sutherland project structural engineer, the warehouse was constructed to a tight building

program which would not have been achievable without the extensive use of precast concrete elements. Mobile cranes with loading capacities between 90 and 250 tonnes were used to lift the columns and panels off the casting beds into their final positions. To cater for the wind loading on the two gable ends, a comparative cost analysis showed that it was far more economical to resolve these large forces using large precast concrete cantilever columns rather than any other construction method. Initially, five of these columns were placed along the southern gable end and spaced at around 40m apart. Internal tenant requirements, to some extent, played a role in choosing the spacing of these columns. A further five wind load columns will be installed at the northern gable end during the final construction phase. The wind load columns are some of SA’s highest precast concrete columns on an industrial building to date. They were all 600 mm wide and their depths vary between 1,4 and 1,7 m. Their heights range from 20,7 m to 24,8 m and the columns weigh between 30 – 48 tonnes. The foundations are equally formidable. Smaller intermediate precast columns, between 10 and 13 m high, were also incorporated into the gable ends and were extended to roof height using structural steel sections. Eighty precast columns on relatively large concrete foundations were used on the eve elevations. These columns measured 800 x 500 mm x 8 m high and were extended to 20 m using structural steel. The extension heights were again chosen to achieve an economical balance between practical considerations, material costs and plant hire costs. Similarly, 10 m precast columns were used inside the building and

The wind-load columns’ starter bars were meshed with the column-base rebar.

24 CONSTRUCTION WORLD JUNE 2022