Construction of the Oxford Parks development, in Rosebank, has progressed, with the first building, built by Concor Buildings to serve as the new head office of oil company BP South Africa, completed.
The 4-star green rated building is part of Phase 1 of the Oxford Parks vision, which will include three more office blocks and a hotel in due course.
Work on this first building, for Concor’s client Intaprop, started in August 2017 and had a tight construction schedule of around 16 months, with between 300 and 350 employees and contractors on site at the project’s peak.
The main structure of the building required 17 000 m3 of concrete, coupled with 2 100 t of reinforcing. By the end of May last year, around 780 000 bricks had been laid for the building.
Martitz says the wedge-shape design of the building is notable for its stunning glass façades, which were created using 4 500 m2 of glazing, allowing ample fresh air, natural daylight and vast views looking east over Johannesburg.
However, to deal with the sun’s heat through the glazing – without overloading the air conditioning system – Concor included a double-ventilation façade on the front of the building, involving two layers of glazing that are 40 cm apart. The outside layer is open at the bottom and at the top, allowing air to rise and exit this vertical channel as it heats, sucking in cooler air at the bottom and keeping the building cool.
Additionally, Concor installed an automated horizontal blinds system that is linked to a weather station. Guided by the season and time of day, the angle of the blinds controls the entry of direct light into the building, which further promotes energy efficiency.
With the building located directly above and near the Gautrain tunnel, it posed particular challenges for the design of foundations for the building’s basement.
“Foundations were not conventional piling and pile caps but were raft foundations due to the restriction zones of working above the Gautrain tunnel,” notes Maritz.
Adding to this complication were the highly collapsible soils which, in the case of rain, could have fallen into the foundation trenches. Given the large amount of steel reinforcing required in the raft foundations, the recovery of collapsed trenches could have become costly and time-consuming.
“Excavations started in August 2017, but we mitigated the rainfall risk by fast-tracking this phase and we were able to complete the foundations almost a month ahead of schedule, before any heavy rains arrived,” he says.
Being a residential area, there was also a restriction on working hours due to noise, meaning that work had to stop every day by 18:00 and by 14:00 on Saturdays. No work was permitted on Sundays.
“This made it necessary, for instance, to conduct our large concrete pours promptly in the morning, so that there was time to complete the slab before the end of the working day and limit the noise to floating activities,” Maritz points out.
He emphasises that good planning, time sensitivity and efficiency were all the order of the day in keeping the project’s timeline on track. This included installing the glass façades in good time as several tasks, like finishing trades, could only be finalised when the building was fully enclosed.
Source : http://www.engineeringnews.co.za/article/first-oxford-parks-building-completed-2019-01-17