Capitec Project Ikhaya is a modern, open office building intended to provide a free-flowing collaborative work environment. The structure is predominantly concrete framed, but structural steel and composite steel and concrete construction was used in a complimentary way.

The bridge links and the floor over the main entrance require light, long-span structures with limited headroom implications. The parking structure required the use of a solution that would be removable in the long term to allow conversion of the building for a different use.

A brief description of the structural framing

HQ Walkway Bridges
Macsteel / Westok Cellular Beams with Bond-Dek composite flooring

HQ Main Entrance Floors
Macsteel / Westok Cellular Beams with Bond-Dek composite flooring
– Macsteel / Westok Ultra-Shallow Floor Beams with Voidcon permanent formwork floors spanning between floor beams

HQ Roof
– I-Section portal frames with transfer systems supporting rectangular hollow section roof light pods

HQ Entrance Canopy
– I-Section roof framing; supported on slanted circular hollow section columns

Parking Structure Infill Floors
– H-Section columns supporting I-Section composite floor beams with Bond-Dek composite flooring

Were there any challenges in the fabrication of the project from the engineer’s design ?

From a fabrication and erection point of view the most critical parts were related to the composite floors and walkways.

  • Cellular and USFB members are manufactured in Gauteng, resulting in lead times to be factored in carefully on an accelerated construction program.
  • The manufacturing process of the USFB required delicate craftsmanship from the coded welders, as the different web thicknesses required sufficient weld prep to ensure perfect assembling and efficient weld penetration, in order to pass NDT testing.
  • Cast-in items providing supports required careful planning and coordination due to the faster than originally planned concrete frame construction. In some instances, it was necessary to resort to infill casts and coming back later to install cast-in components.
  • Level and setting out control were tight and required careful coordination
  • Temporary supports for the long-span multi-level systems were intricate and obstructive to other construction activities
  • Due to the use of hangers to support the composite floors in the entrance area and the requirement for propped construction; construction of the composite infill had to be from the top down

What is most impressive about this project from a technical perspective?

Geometrically the building is quite complex due to the curve-linear shape of the superstructure. The shape combined with the height restrictions on the site and the mismatch between the column grid in the lower parking levels resulted in a complicated structural frame.

Furthermore, there was a requirement to have long-span pedestrian bridges crossing the central building atrium and the need for a very open reception area. Combining this with a shallow ceiling system and exposed concrete soffits forming a specific design language throughout the building posed challenges.

The pedestrian bridges crossing the atrium had more ceiling space available and also served as links for services crossings. The use of composite cellular beams provided a cost-effective long span system that could cater to the dynamic performance requirements and allow services to cross without paying the penalty in terms of weight.

The ceiling configurations above the main entrance resulted in a very shallow available floor depth and a long span. The total span in this area between columns is 18m. Bridging this span was done by using a thickened reinforced concrete floor cantilevering over the support columns, supporting a simply supported Ultra-Shallow Floor Beam (USFB) system spanning almost 13m. The USFB system comprises of asymmetric steel sections with circular voids in the webs. The top flanges are narrower to allow permanent formwork to be dropped in, to span from beam to beam, resting on the bottom flanges. Composite action is achieved by using conventional reinforcing bars placed in the web openings (bars perpendicular to the beam span; plug composite action) Due to the long spans a propped construction methodology was adopted to limit the final deflection.

To complicate matters further, the tips of the concrete edges supporting the USFB floor system on the building edge, had to be column-free at ground level to create a weather canopy. This was accommodated by suspending the perimeter of the 1st and 2nd floors using high capacity rods from a cantilever transfer beam at roof level

How does this project demonstrate the benefits of steel as a material?

Steel can be used successfully in combination with more conventional concrete construction in a complimentary way. Some structural systems and configurations necessitate the use of steel with its long-span and overall weight reduction capabilities.

What is special/ unusual/ innovative/ aesthetic about the steelwork in this project?

This is not really applicable, since the structural framing is largely concealed by cladding and ceiling systems.

How did the project team work together?

The use of Building Information Models (BIM), representative of the actual construction, assisted greatly in ensuring that all parties involved clearly understood the configuration of the planned structure and how the various components interacted.

In addition to this, an open mind from the Contractor’s team to implement something out of the ordinary assisted in getting the job done.

Project motivation editorials are provided by the project nominator. If any technical details, company names or product names are incorrect, please notify the SAISC so that the error can be corrected.

PROJECT OVERVIEW
Physical address of the project
Street Address
Town
Province
Neutron Road Techno Park
Stellenbosch
Western Cape
GPS Co-ordinates Latitude: 33°57’54.82″S Longitude: 18°49’51.49″E
Google Maps link Closest location on Google Maps http://tiny.cc/u3d0jz
STRUCTURAL STEELWORK
Completion date of steelwork HQ Building – August 2019 Parkade Building – March 2020
Completion date of full project HQ Building – February 2020 Parkade Building – June 2020
Tonnage and steel profiles used 475t
Project Team Role Company
Nominator Macsteel Trading
Client/ Developer Capitec Properties (Pty) Ltd
Architect DHK
Structural Engineer AECOM
Engineer AECOM
Quantity Surveyor De Leeuw Stellenbosch
Project Manager SIP PM
Main Contractor WBHO
Steelwork Contractor LJ le Roux Industries (PTY) LTD
Steel Erector LJ le Roux Industries (PTY) LTD
Photographer, Photo competition Terry February Photography

If you were a part of this project, and your company details are incorrect or missing – please notify the SAISC so that the error can be corrected.