CRC building in Rivonia a monument to engineering innovation

Site Progress


26-07-2019
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Concrete Trends
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The new Christian Revival Church (CRC) on the corner of Witkoppen and Riverbend Roads in Fourways is an architectural and structural-engineering feat that showcases excellence in the design and application of steel and concrete technologies.

It also bears testament to the skills and capabilities of DBM Architects and Fortem Consulting Engineers, as well as the principal contractor, Mike Buyskes Construction, which executed the technically complex design with meticulous precision.

Among the many stand-out features of the building is the spiral ramp in the entrance hall. Starting at the lower parking basement, it provides the about 6 000 congregants with safe and convenient access to all four levels of the building.

It is suspended from the roof via a circular reinforced concrete beam-and-slab system that is supported by a central reinforced concrete column.

The slab-and-beam system is braced by perimeter columns and beams which also support the building’s glass façade. Suspended from the slab-and-beam system, slender steel hangers with adjustable couplers support the inner steel stringer channels. The latter are connected to the outer steel stringer channels, braced at various points to the columns surrounding the ramp, with I-beams. A reinforced concrete slab that forms the floor of the ramp is supported between the two stringers and intermediate I-beams for the length of the spiral ramp.

Another engineering highlight is the steel ring that supports the concrete staircase leading from the one side of the triple-volume entrance atrium. It fulfils a critical aesthetic function by eliminating the need for reinforced concrete columns extending from the first to the second landing.

The base of the structure is supported on either side by a reinforced concrete column located beneath the landing of the first flight. It circumvents the first flight’s staircase landing and connects with the base of the second staircase at the apex of the circle. The structure is fixed to the base of the second flight staircase landing and at either side of the landing of the first flight to provide stability.

Another highlight of the church is the auditorium’s 14 m cantilevered balcony. An in-situ-cast raking beam, which was pre-cambered to minimise long-term deflection, supports precast-concrete seating slabs. This upper gallery seating area has no columns below that would obscure views of the stage.

Both the entire lower and upper auditorium area for the 4 500 congregants is enclosed by a curved structural steel roof that is supported by seven 1,9m-deep and 2,4m-wide triangular-shaped roof trusses.

These “Toblerone” trusses were fabricated from a variety of circular hollow sections with two top chords and one bottom chord connected with diagonal members along the span.

The top chords are braced together with horizontal circular members, while intermediate support is provided by a curved ring beam located at different points along the length of the trusses and which form the rear perimeter of the auditorium.

In order to reduce load on the 8000m2 elevated parking structure to provide cost savings in the foundations and columns, Fortem Consulting Engineers’ Director, Hans Koorn, recommended the use of SCP 327 as a waterproofing agent.

This is opposed to the traditional approach of waterproofing parking decks by first applying a thin impermeable membrane and then constructing a sacrificial asphalt overlay or paving blocks that increase the overall weight of the slab.

SCP 327 is known for its ability to enhance and improve concrete performance throughout its service life.

The product penetrates into the capillaries and pores of reinforced concrete structures to protect the embedded reinforcing steel. Once it has reacted with the free alkali, it forms a Calcium Silicate Hydrate gel within the concrete capillary and pore structure to reduce water migration to levels acceptable for most adhesives, coatings and coverings.

International tests have shown that concrete treated with SCP 327 is able to withstand 100m of head pressure, while the full range of Spray-Lock Concrete Protection products continue to undergo extensive testing worldwide, including in South Africa by the University of Cape Town’s Department of Civil Engineering.

Notably, Spray-Lock Concrete Protection products are also known for increasing concrete durability to provide longer lasting and less maintenance-intensive concrete structures.

Koorn and his team were first introduced to SCP 327 by Leonard Scott-Turner, Managing Director of Concrete Junction, and Carl White, Managing Director of Creative Engineering.

Creative Engineering is the South African agent for the full range of Spray-Lock Concrete Protection products and Concrete Junction, the approved applicator.

“The product has been used on many large international projects, including bridges, ports and wastewater treatment plants considering its ability to also improve the compressive and flexural strength, as well as the density of the concrete. These were also other notable advantages of SCP 327, although the quality of the concrete on this project already was of an exceptionally high standard before being treated with SCP327,” Koorn says.

Importantly, SCP 327 also acts as a curing compound for new concrete and, therefore, eliminates the need for water curing/ponding. Due to design strengths being reached earlier, formwork stripping times can be reduced. This was a major additional benefit for Mike Buyskes Construction, which was working to extremely tight deadlines.

Concrete Junction applied the treatment within two to three hours after the concrete had been power floated, with a litre of SCP 327 covering a surface area of about five square metres. The treatment proved to be successful in drastically reducing shrinkage, in addition to acting as a curing compound and moisture barrier.

As advised by Concrete Junction and the Creative Engineering, critical areas, such as construction and expansion joints, were treated separately. Hydrophilic water stops were placed at the construction joints and Polyurea then applied over both the construction and expansion joints.

As a leader in the field of waterproofing, expansion-joint sealing, as well as concrete repairs and rehabilitation, Concrete Junction assisted Fortem Consulting Engineers with the design of the treatment of these critical areas.

Both White and Scott-Tuner conclude by noting that they are proud to be associated with a prestigious project that has already received so much acclaim for innovation by the South African built-environment profession, and look forward to continuing their long working relationship with Fortem Consulting Engineers.

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