The Leonardo, cousin to the Legacy Group’s Michelangelo and Da Vinci buildings, will ultimately be the tallest building in Sandton, having been boosted from an original 47 to 55 storeys due to demand, with an anticipated final height in excess of 223m upon its completion in 2019. It is fitting that PERI, the world’s largest manufacturer of formwork and scaffolding, has been involved with this iconic project since 2015.
“The challenges have been many and varied – and we have enjoyed rising to every one of them. When the Legacy Group awarded our long-time client Aveng Grinaker-LTA the contract to build The Leonardo, we were awarded the basement levels initially, with the top structure to follow,” PERI Lead Engineer: Key and Strategic Projects Sebastian Burwitz explains.
While PERI South Africa has collaborated with Aveng Grinaker-LTA on a number of flagship projects, including the recently-completed Sasol headquarters, The Leonardo is the largest project to date for both companies.
The basement development alone included pouring and placing a total of 17 500 m³ of reinforced concrete, 1 380 tonnes of reinforcing steel, 40 000 m² of formwork, and the laying of 350 000 stock bricks, together with 8 000 m² of plaster, and 2 000 m² of screed.
In planning the basement slabs, PERI incorporated and supplemented Aveng Grinaker-LTA’s own stock of SKYDECK, its panelised slab formwork system, into the formwork layouts. Together with PERI’s MULTIFLEX, used in adjacent slab areas, the required slab loadings could be carried in the most efficient manner.
For the standard gang-formed vertical applications, PERI’s TRIO wall formwork system was used by Aveng Grinaker-LTA, with supplementary stock supplied by PERI to site. PERI’s manhandled DOMINO system was used to eliminate dependency on crane time for the internal walls and beam sides.
“PERI was able to use its innovative DUO system with polymer technology, also characterised by its low weight and extremely simple handling,” Burwitz adds, noting that the feedback to date has been very positive. “Aveng Grinaker-LTA has subsequently deployed DUO project-wide for ancillary works such as some water tanks and smaller retaining walls, where the system has really come into its own.”
The main focus for PERI was the gigantic core. Consisting of over 1 000 m2 of core walls, this is the centrepiece of Sandton’s tallest building. The core and slabwork have been staggered on purpose to allow for efficient access to shafts from slab level, and to maximise cranage advantage.
As a mixed-use development, The Leonardo will offer luxury residential apartments and penthouse suites, together with more than 15 000 m² of premium office space. It includes a business and conference centre, a gym and spa, restaurants, and recreational and lifestyle zones.
“We have been on-site since Q4 2015, commencing with the supplementary supply of PERI-owned materials that our client had in its yard.” Burwitz highlights that the main engineering goal was to complete the core design within budget and time constraints, as per the programme specified by the client. “Getting our heads around the sheer size and scope of the project was an important initial mental step,” he notes.
The 11-m-high key feature walls posed a particular challenge in that the patterns specified had to meet strict quality and design criteria. It was decided to cast these walls on-site as single elements, with close collaboration with suppliers in terms of the concrete mix required, the use of external vibrators to settle the concrete inside the form, and then the unusual feat of pumping concrete from the bottom-up firstly, and later from the top down. Here the correct sequencing was vital.
Extra attention had to be paid to health and safety in terms of the extreme height of the building, especially in terms of wind speed and pressure analysis for working at such heights. Here PERI provided dedicated training on its Rail Climbing System – Carriage (RCS-C) heavy-duty system. This training extended to toolbox talks with all foremen to ensure that they not only understood how the system worked, but how best to use it to speed up construction and ensure maximum quality.
PERI’s ongoing involvement with the development of the ‘New Sandton’ has seen the formwork and scaffolding solutions provider involved with 60% to 70% of all the major buildings in the premier business precinct since 2015, from full supply to specialised items.
“The combination of our products, customer relationships, and engineering expertise and solutions, as well as our important international engineering back-up when required, makes PERI a ‘go-to’ supplier,” Burwitz concludes.
PERI project team
Project technical support: William Ndou
Formwork concept and design: Chris Heesen, Sebastian Burwitz, and Stephen Sprong
Commercial: Billy van Straaten