Royal Bank of Scotland Headquarters, Gogarburn, The
The Royal Bank of Scotland (RBS) is one of the world’s largest financial organisations. The Bank’s vision for Gogarburn was to construct a headquarters that would provide a world-class working environment and to create a business campus that would help position the bank as the employer of choice in financial services.
CERTIFICATE OF EXCELLENCE
In just three years the vision was complete and the campus was open for business. At the outset. RBS talked of creating all the provisions that could he expected from a small village to allow staff to balance their working day with their personal lives. Gogarhurn is the epitome of a building that combines work-life balance.
At the heart of the campus is a 280m internal street lined with a range of high street shops to which the business houses are connected. The seven business houses are three storeys and are 18m wide. The geometry of the building is a response to the curve of the underlying topography of the site and the necessity to retain the magnificent mature trees by integrating them with the business house courtyards.
The articulation of the plan naturally breaks the street into three distinct sections linked by squares lit by natural daylight which bring the landscape into the street, provide views and give a variety of settings for informal meetings, break-out areas and touchdown spaces. The workspace is arranged in regular, flexible floor plates to provide continuous openplan space with cores located off the street.
The development also includes a Leisure Centre, Nursery, Conference Centre and the refurbished Gogarburn House. In total, the total gross area of all the buildings is 74.484m^sup 2^ on a 40ha campus.
Foundations and basements
The underlying boulder clay provided a competent founding stratum. Extensive cone-penetration test surveys allowed the stratum to be mapped and the optimum level of the basement to be determined. This allowed the footprint of the business houses within the basement area to be founded on pads: they were piled where they extended beyond the basement footprint. A high water-table level and the 1-in-200 floodplain requirement of the Gogar Burn were also taken into account.
On the higher northern side of the basement, a lined contiguous piled wall was bored into a preformed cement/bentonite slurry-filled trench. The slurry trench spanned the piles and provided water and soil retention during the basement construction. The car parking areas were designed fora BS 8102(1) Grade 2 environment with local areas being enhanced to Grade 3.
At concept design stage, an evaluation was made to determine the optimum construction technique for the structural frame of the business houses. The final decision was based primarily on both cost and efficiency but took into account other influencing factors such as sustainability and design adaptability. During the evaluation, 13 superstructure options, three ground-floor options and two substructure options were assessed. These were matched to the mechanical and electrical services options to give an integrated building solution. The 13 options were considered under a number of headings, including:
* floor-to-floor height
* ceiling form/finish quality
* floor-plate flexibility
* frame sustuinubility
* service openings/structural flexibility
* complexity of service integration
* façade integration
A post-tensioned flat slab supported by precast columns on a 9 × 9m grid proved to be the optimum solution, with lateral stability being provided by structural concrete walls, continuous through the height of the building. The solution allowed the use of precast concrete and offsite manufacture us much as possible, reducing on-site waste, dust and labour. Where this was not possible, the project was able to have an on-site concrete manufacturing facility and so minimised production waste and the impact of construction vehicle movements on the local network. Post-tensioning of the Hoor plate increased clear spans over the concrete frame and the thin slabs reduced the overall building height. This offered savings on external cladding materials and there is less volume and embedded energy to the building.
Flat floor soffitts meant that the space within the ceiling void was maximised for distribution of building services and the simplified formwork allowed fast-build construction turnaround, giving programme efficiencies and a reduction in preliminary costs. The columns of the business houses are supported directly off the top of the pad foundations or slab thickenings over single piles. They are exposed within the basement and the business houses.
The basement, ground- and upper-floor plates were all analysed using finite-element techniques. Very early in the two-stage tender process, consultant engineer WSP was able to nominate the reinforcement bar diameters that would be excluded from the project. This assisted the pricing of reinforcement as at that time steel prices were fluctuating considerably. WSP determined a base mat to all traditionally reinforced floor areas. This was typically pitched at 200mm centres. The base mat was then enhanced at 200mm centres using straight loose bars at locations to suit shear and moment influence plots. This enabled detailing to commence early and reduced the amount of reinforcement installation drawing and schedules and greatly eased the fixing on site. Reinforcement fixing peaked at 250 tonnes per week and was sustained over a live-week period.
Each of the business houses is treated as an independent structure when considering stability, which is provided by the in-situ concrete shear walls around stairs and isolated areas in the main cores. The location, number, size and orientation of these in-situ concrete walls have been carefully determined to ensure they are kept to a minimum and are compatible with the post-tensioning. The load-bearing columns are designed as pin ended and do not contribute to the overall stability of the structure.
Opened by HM the Queen in September 2005, the RBS facility is very impressive. Innovative use of post-tensioned floors, with large reusable floor slab table’ forms and precast tensioning frames, provided for early tensioning and, therefore, very rapid construction. The project team claimed ‘excellence’in sustainability for the project with on-site batching of the concrete, using materials quarried locally, thus saving on long-haul routes.
Precast concrete columns were used to accelerate floor construction, producing a very smooth, almost polished finish. Design was complicated by differential ground conditions, which meant foundation types had to change, yet the building appeared seamless. This is an iconic project In which concrete has been used extensively and well. In terms of the modern built environment, concrete played a vital part in allowing RBS to achieve its aspirations.
The Royal Bank of Scotland Headquarters, Gogarburn
Owner: The Royal Bank of Scotland Group
Architect: Michael Laird Archttects/RHWL JV
Consulting engineer: WSP Group
Services engineer: WSP Group
Main contractor: Mace
Glass roof to street consultant: SKM
Concrete package contractor: Laing O’Rourke
Precast concrete and stone supplier: Loveld NV
Piling contractor: Stent
Prestressing subcontractor: Strongforce
1. BRITISH STANDARDS INSTITUTE. BS 8102. Code of practice for protection of structures against water from the ground. 1990.
Copyright The Concrete Society Nov 2006
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