Close collaboration with Arup and the building’s original drawings helped RKD design the Gravity Bar Extension with minimal intervention
A deftly-engineered extension to Ireland’s first ever mild steel building, the Guinness Storehouse in Dublin, is one of the innovative projects shortlisted for this year’s Structural Awards run by the Institution of Structural Engineers.
The Gravity Bar Extension, designed by RKD Architects with Arup as structural designer, is shortlisted for the Minimal Structural Intervention award, which recognises ingenious designs that resulted in no, or minimal, structural interventions to extend the life of an existing structure.
The challenging project involved both a vertical extension to the 1904-built structure and a horizontal extension to the existing panoramic Gravity Bar on the roof, built in 1999, to triple its footprint. The tourist attraction has over 1.7 million visitors a year and the project had to be delivered while the building remained fully operational.
The original Storehouse served as a fermentation plant for the St. James's Gate Brewery and was designed in the style of the Chicago School of Architecture. The riveted plated structure mimics that of the Eiffel Tower, completed in 1889, but built in mild steel it is much stronger than the latter’s wrought iron, putting it at the forefront of modern construction.
Extensive initial investigation work, including tensile tests and chemical analysis, was required to verify the structure’s physical properties and establish its load bearing capacity.
‘The Guinness Archives had the original 1902 drawings of the foundations on file, so we used those to determine the situation with the foundations,’ said Noel Sheridan, associate at Arup. ‘3D point cloud surveys of the structure allowed us to more accurately determine column sizes and build up.’
Analysis confirmed that the structure did not require any strengthening work and that the existing columns could be retained throughout, apart from on the top floor, where columns intended only to support a lightweight roof had to be replaced.
New columns spring up from the original columns to support the extension, minimising penetrations through in the roof fabric to benefit conservation and keep the facility watertight throughout the works.
‘From an architectural point of view, it was very challenging. The architect had to design the extension on the original column grid to avoid the need for a transfer at roof level, which would have meant removing a large portion of the roof,’ says Sheridan. ‘The drive to minimise structural intervention really did start at scheme design stage, with strong collaboration between Arup and RKD: if we didn't get it right large portions of the structure would have had to be removed.’
Other building projects shortlisted in this award category include the refurbishment and extension of Cambridge House, a 100-year-old building at Birkbeck College, University of London. The refurbishment of the Royal College of Obstetricians and Gynaecologists in Union Street in London unites two existing structures, a Victorian hop warehouse and a 1980s office block, primarily through the addition of a new atrium and staircase.
The Structural Awards 2021 aim to acknowledge the best global engineering projects from the past two years. The winners will be announced at an event in London on 5 November.