Consulting engineering firm Aurecon’s R70-million project involving the construction of a study centre at the University of Pretoria’s Engineering 1 building, which comprises 158 t of structural steel, is scheduled for completion this month.

It was decided in October 2011 to upgrade the university’s existing Engineering 1 building to provide a place for engineering students to work on group projects after hours.

Moreover, owing to the country’s ever-growing demand for engineers in the public and private sectors, the university faces the continual challenge of having to expand its engineering facilities to accommodate increasing student numbers and provide them with the necessary facilities.

“The new study centre, equipped with the latest computer technology, will accommodate students close to the main lecture halls and facilitate learning and group work, especially for students who do not have supportive home environments or housing on campus,” says Aurecon buildings technical director Johann Weinmann.

He adds that the new structure was planned and designed for construction at street level in a previously unexploited space of the existing Engineering 1 building, above the existing basement lecture halls.

By adding an additional 3 000 m² to the existing Engineering 1 building, the study centre consists mainly of an arched roof structure and a mezzanine floor and can accommodate about 800 students.

Weinmann says the study centre is a good example of the ability and versatility of steel to provide durable, aesthetically pleasing structural solutions that improve the use of available space.

Why Use Steel?
Weinmann says three factors – the weight of the new structure, fire protection requirements and aesthetic appeal – were taken into account when the decision to use steel was made.

“A steel structure was the only solution, from a design and practical construction point of view, to best achieve the required design criteria,” he adds.

One of the main reasons for selecting steel as the structural medium was that the additional load that would be added to the existing structure could be reduced, as the new building was located directly above the existing lecture halls in the basement below.

Steel is the most common material used for long-span structures, owing to its high strength-to-weight ratio, ease of fabrication and erection, as well as lower cost.

Moreover, the client made it clear that modifying the existing building foundations below to accommodate the new structure was not an option; therefore, reducing the new structure’s weight was critical to achieve the required design criteria, notes Weinmann.

Meanwhile, owing to a required 60-minute fire rating, lightweight IPE-grade steel sections were treated with intumescent paint and were used instead of timber for the mezzanine floor.

“Steel, as the main design medium, also plays a crucial role in achieving the required aesthetic shape and appeal of the final building. Much of the structural steelwork will be visible to the public after completion of the project, as the aesthetics of steelwork was a significant consideration in determining the design solution,” explains Weinmann.

By exploiting the flexibility of steel, it was possible to roll large steel sections to create the visually appealing dome-type roof and leaving much of the steel members and the connections exposed to complement the dome roof and façade.

“The practical, creative and successful use of steelwork also led to the challenging time and budget constraints being met,” says Weinmann.

One of the benefits of using steel, specifically for this project, is that it is the least intrusive construction method as the steel sections are fabricated off site, thus, reducing the amount of construction activities on site, says Weinmann.

The study centre is built in the middle of the university’s botanical garden, with several endangered plant species growing virtually against the building’s footprint.

Careful design and meticulous planning throughout the construction phase was needed to avoid doing any harm to the surrounding environment, notes Weinmann.

Building Components
Despite the building mainly consisting of structural steel, some concrete elements, such as pile foundations and a100 kl rainwater storage tank, have been included.

The pile foundations and pile caps are designed to resist the horizontal reaction of the arched steel roof, which ensures that the arch beam stays in a compression state to avoid any unnecessary weight on the existing building foundations. The rainwater storage tank, situated beneath the western entrance, is used for rainwater harvesting and reuse in the surrounding botanical garden.

The structural steel used to construct the study centre was supplied by steel producer ArcelorMittal South Africa and JSE-listed steel and vanadium producer Evraz Highveld and includes cost-effective and locally manufactured steel sheets.

The arch-shaped roof structure is clad with locally produced steel roof sheeting as the imported sheeting required for the original two-way curved roof shape was not economically viable.

Other steel components used in the study centre include tubular sections, which are used on both the interior and exterior front of the structure.

Weinmann explains that the study centre’s roof is supported by six internal 356-mm-diameter circular hollow section columns and is braced by 89-mm-diameter aesthetically pleasing circular hollow sections.

The western canopy roof and front is supported by 200 mm x 100 mm rectangular hollow columns, which have a radial flare arrangement.

Further, radial support beams were formed through rolling standard I-beam sections into shape, and are used to support sun control louvres.

Challenge
Weinmann says that fabricating the beams was a significant challenge, as there is only one South African company that has machines capable of rolling such large steel sections and these machines broke down halfway through the rolling process, which stopped work on the project.

The steel-rolling company informed the project team that an estimated delay of 20 working days was anticipated and since the roof closure was the project’s critical path, the delay would affect most of the work on site.

The client subsequently requested that the structural engineers investigate alternative manufacturing options for the steel sections, which involved fabricating radial steel-plate girders from scratch.

Based on time and cost implications, it was decided that the construction programme should absorb the 20-day delay and that the contractor should complete the rolling process as originally planned, notes Katranas, adding that sourcing another cold-rolling company was not viable in the limited South African market.

However, cooperation among members of the entire project team to work around the delays caused by the breakdown of the cold rolling plant contributed to the project’s success, he says.