SSDA 2023: One Centenary Way, Birmingham

Featuring an expressed steel exoskeleton on all four elevations, Birmingham’s One Centenary Way is a standout commercial development in more ways than one. Below ground level, the steelwork is equally impressive. Just over 60% of the total footprint sits on top of a series of storey-high trusses that span the A38 dual-carriageway tunnel.

“One Centenary Way is an important building for Birmingham, not least for its green credentials, but it’s also the first commercial exoskeleton building in the region,” says Dav Bansal, partner at Glenn Howells Architects. 

Approximately 1,950 tonnes of the 7,450 tonnes of structural steelwork was used to fabricate the 12 trusses, which are up to 34.5m long and weigh up 130 tonnes.

Fabricated at BHC’s Lanarkshire facility, the trusses were transported to site as complete sections, up to 6.15m wide. On site, a 1,200-tonne capacity mobile crane – one of the largest in the UK – erected the trusses.

The trusses form part of the basement level and their top chords help create a platform to support the majority of the building’s structural frame. One of the two basement levels is accommodated within the trusses’ depth. This upper basement floor houses a well-equipped and accessible cycle hub for the estate.

Due to the tight site constraints, a typical load-bearing core with columns going into the ground to hold the building up and give it stability was not an option. The project’s design team’s solution was to use the building’s facade to provide the stability in the form of a Vierendeel exoskeleton. 

As well as the stability provided by the exoskeleton, a centrally positioned steel braced core provides rigidity. “The exoskeleton on its own doesn’t provide enough stiffness for the overall structure, so the two stability systems work in tandem,” explains Ramboll principal engineer Daniel Yoxall.

The project used a steel core, instead of a concrete one, as a lighter solution. This was important, as the core had to be positioned on top of the trusses, so it could sit in a central position within the building to satisfy the internal office layout.

The Vierendeel exoskeleton is formed with a series of vertical and horizontal steel sections forming 12m-wide rectangular boxes. The rectangles incorporate 3m-wide horizontal windows, encased within an exposed structural steel facade.

The interior of the building offers large office floorplates, as well as retail space at ground floor level. The column grid is based around a 12m × 9m spacing, as this layout requires minimal internal columns, to provide an open-plan office layout.

The ground floor also has a triple-height reception area with a floor-to-ceiling height exceeding 9.5m. To accommodate this impressive reception, the first floor does not cover the entire building footprint. The upper floors have a standard 3.8m floor-to-ceiling height.

Summing up, the judges say this elegant, exposed steel structure springs off a system of trusses spanning a busy road tunnel. Despite depths of over 6m and the biggest weighing 130 tonnes, the trusses were transported to site and installed fully assembled.

The result is a high-quality office building with excellent sustainability credentials, which has helped transform this area into a pedestrian-friendly campus.

Produced by BCSA and Steel for Life in association with Construction Management