The 15500m² building is the latest addition to the mixed use precinct of Menlyn Maine. Its primary purpose is for offices, with a small retail space at ground floor level. It is envisioned that the retail space be operated as a restaurant / deli for the office users as well as providing another alternative to the Menlyn Maine Central Square retail development.



The buildings within Menlyn Maine are built onto the boundary line, thereby responding directly to the urban streetscape as well as defining it.  Associated retail space with external spill out balconies activates the streetscape and provide an additional layer of security by means of ‘eyes-on-the-street’.

The Architectural Brief

The brief was to design a unifying element which ties all of the levels together seamlessly, whilst complementing the volume and geometry of the atrium which hosts it. The client wanted the stair to not seem alien in the space, but rather to blend seamlessly with the surrounds. It was envisioned that the staircase would form a talking point to onlookers, and a unifying interior feature to all floors.

At the heart of the building, the multiple-volume atrium functions as a gathering space in the semi-public ground floor. Flanking the northern side of the atrium, the design of the atrium stair is based on the notion of a stair as a social interaction space – an area where people have a chance meeting or interact socially. The stair becomes the platform of showcasing and animating vertical movement in the atrium space, thereby optimistically engendering the use of the stair in lieu of the lifts. The seamless wrapping of the atrium-passage balustrade with the atrium staircase, visually connects the various levels and aids in contextualising human-scale and experience.

Why Steel was used

In conception stage, the materiality came secondary to the design. The staircase was designed to be intricate and organic, with the curves and proportions carefully manipulated to suit the space and adjacent features. Once the team were happy with the design, it became very clear that the only way in which the staircase would be structurally and visually achievable would be if it was constructed from steel. Due to the spans, WSP had recommended that the staircase be built from steel to reduce the self-weight of the structure.  It was integral to the design that the staircase cantilevers from a slab edge with no intermediate supports.  Initially the architect proposed this staircase to be constructed out of concrete however inevitably steel was the only material which made this possible.

Structural Framing

A combination of straight and curved I beam stringers were used on either side of the stair, with large base plates on either end welded to cast-in supports on the slab edges. All slab edges had to be significantly strengthened to host the stringers. Angle irons were welded to the stringers at very specific intervals to host a Vastrap plate, which in turn hosted a solid timber tread. The careful coordination, sizing and positioning of the steel elements ensured that the finishes junction perfectly with one another.

The most impressive technical aspect of this staircase is that the staircase could be 100% manufactured off site, and installed as a retro-fit item. The precision of the staircase, and the complexity of the installation makes this quite an accomplishment.  This is not a traditional half pace stair since one side of the risers are angled away. This created an eccentric support. Additionally the deflection of the structure had to be limited as glass balustrades were to be used. Individual cast in frames had to be placed and cast with great accuracy to ensure accurate post fitment of the face plates onto the protruding bars. The site welding quality and monitoring was of great importance since these large staircases are supported at the stinger ends, welded to the face plates and horizontal anchor plates with 10mm prepared welds. With 21 meters of vertical up, 8 meters of overhead and 10 meters of down hand welds, daily tracking, inspecting and doing non-destructive weld testing was done to ensure each staircase meets with the design requirement before lifting the next staircase into position. With the cast in frame in place and additional re-bar at these positions to strengthen the slab edge, fitting the 120 number of M24 RE 500 chemical anchors into position was always going to be difficult. The rebar and cast in frame positions were scanned and marked out on the slab surface in order to drill and fit these anchors into position.  Once the anchor positions were determined and drilled, the anchor plates were match drilled to suit each anchor position.

Challenges

The biggest challenge was the enormous weight of the staircase in terms of dead and imposed live loads, along with the millimetre precision which was required to make all interfaces perfect. With each stair weighing close to 4 tonnes in steel alone, a maximum of 2 stairs could be placed on the ground floor slab before the slab would collapse. Each staircase had to be split into two pieces at landing level in order to be able to transport the pieces to site and lift them over the building, into the atrium in order to fit the pieces into place with the tower crane. In order to achieve the level of accuracy, each staircase built complete in a jig during fabrication. Welding distortion was of great concern and had to be closely monitored in the workshop to ensure the large pieces remained within tolerance. Once on-site, each piece was lowered into place, supported on scaffolding props, bolted at landing level and welded to the vertical faceplates at the slab edges whilst suspended. Because each staircase had to be constructed in two pieces and welded to faceplates, considerable site welding had to be done.

How this project demonstrates the benefit of steel as a material

This staircase would not have been possible should any other material be used. The cantilever from a concrete slab edge, along with the weight which the stair is able to support (an African elephant on the landing) could not be done with anything other than steel. WSP was able to reduce the self-weight of the structure and adapt the curves required by the architect.

The precision is by far the most special part of this project. Steel sections are notorious for having quite large tolerances in sizes. In this application, there was simply no room for tolerance or errors. Between the Architects’ detailing, the engineer’s sizing, and the supplier’s detail drawings and manufacturing, each element married perfectly.

How the project team worked together

More meetings were had about this staircase than any other element in the building. It was important that each party involved was 100% up to speed with what was required, and how we planned on achieving it. Given the complexity of the curves, fixings and junctions, it was sometimes impossible to communicate on drawings or over emails. For this reason, Boogertman and Partners made use of 3D printing technology, 3D visualizing technology and very strong software to communicate the intent to all consultants. Once on-site, the main contractor made use of all of these tools to clarify the intricacies with all installers involved.  WSP was in constant communication with the site team, especially with respect to the level of accuracy required to ensure that the connection points lined out. 

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 
197 Amarand Ave 
Menlyn Maine 
Pretoria   
Google Maps link  https://www.google.co.za/maps/dir//-25.7862173,28.2821603/@-25.7865583,28.2822444,18z   

STRUCTURAL STEELWORK 
Completion date of steelwork  04 February 2020 
Completion date of full project  Approx. 20 March’20  
Tonnage and steel profiles used  29ton UB457*191*67 – VT4.5 landings & treads  

Project Team Role

Company

Nominator

Tass Engineering

Client/ Developer

Barrow Properties (Pty) Ltd

 

Menlyn Maine Investment Holdings (Pty) Ltd

Architect

Boogertman Partners

Structural Engineer

WSP, Structures, Africa

Quantity Surveyor

RLB Pentad Quantity Surveyors

Main Contractor

Barrow Construction (PTY) Ltd

Steelwork Contractor

Tass Engineering

Steel Erector

Tass Engineering

Photographer, Photo competition

Tass Engineering

Photographer, Other submitted images

Tass Engineering

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.