Design Awards: 2003: Commendation

Brighton Dome and Museum, Brighton

Brighton Dome and Museum, Brighton

Architect

The Arts team at RHWL

Structural Engineer

Whitby Bird & Partners

Steelwork Contractor

Bourne Steel Ltd

Main Contractor

Skanska UK Building Ltd

Client

Brighton Dome and Museum Development Co Ltd

The 200-year old Brighton Dome, Corn Exchange and Museum buildings are a combination of a unique historical heritage and styles of world importance. They were in need of renewal to sustain their continuing existence.

The buildings were originally commissioned in 1803 by George, Prince of Wales, later the Prince Regent as riding stables and a riding house. They have undergone many changes since then.

The original Dome, which, at 80ft diameter x 65ft high, was the largest timber-framed structure of its type in the world. The Dome was originally supported on a timber ring beam consisting of three wooden sections that circled the building and supported the main Dome Roof, this beam was in turn supported by a series of cast iron supports.

From 1863 until 1930 the Dome was used as Assembly Rooms. The Corn Exchange together with the Museum and Art Gallery were added in 1873. The Pavilion Theatre, seating over 2,000, was formed in the 1930s with the dome auditorium transformed by the addition of an Art Deco ceiling supported by steel trusses beneath the existing timber-framed Dome.

This then, was the first use of structural steelwork on this project. It was used in 1930 to sustain and modernise the building that had originally been constructed in 1803. Now, over 70 years later, steelwork has again been chosen to further extend the life of the buildings.

Part of the project involved the removal of the two proscenium columns added in the 1930s to replace the previous cast iron supports which were replaced by cantilevered beams inserted into the roof space. This involved steel-framed temporary works to support the existing timber Dome and 1930s trusses, then transferring the loads by jacking onto the new steel frame. All of the temporary steelwork and the new permanent steelwork had to be manhandled into the existing buildings and then erected from inside. It was a very difficult and congested site.

This work was successfully completed whilst maintaining the relative level of the existing domed roof structure. No measurable settlement or uplift occurred. Various areas of the refurbishment site are listed as Grade 1 and 2 status meaning that the works had to be carried out with sensitivity to the condition and nature of the existing structures.

Pre-loading of elements and jacking of existing structures were used to prevent excessive deflections. Substantial alterations, such as forming openings in walls, were dealt with by maintaining existing load paths and by spreading stress concentrations through box frames or spreader beams to ensure that the overall load distribution was not significantly altered.

Parts of the existing steelwork that had been dismantled, together with some of the new temporary support steelwork, were re-fabricated and incorporated into the new permanent works. In effect, the steelwork was re-used or re-cycled.

Approximately 500 tonnes of temporary and permanent structural steelwork was installed over a 22 month period between April 2000 and February 2002.

Judges’ Comment

25 Gresham Street, London

25 Gresham Street, London

Architect

Nicholas Grimshaw & Partners

Structural Engineer

Whitby Bird & Partners

Structural Contractor

Rowen Structures Ltd

Main Contractor

Exterior International plc

Client

Asticus (UK) Ltd

25 Gresham Street is a 120,000 sq ft headquarters building providing 10 floors of column free office space. Developed by IVG Asticus Real Estate Ltd and now occupied by Lloyds TSB, it is situated on an island site in the City of London.

The site straddles the remains of a Roman fort and, in locations where foundation piles would otherwise have coincided with an archaeological deposit, the load paths were transferred using steel A-frames within the basement level.

The structure is designed as a braced frame with simply supported floor beams spanning between columns. Fabricated steel sections with an integrated service zone achieved 12m clear spans from the building perimeter to the core. The central braced core provides lateral stability for transverse wind loads and the suspended south elevation. Vertical braced bays in the east and west stair cores provide additional resistance to torsion and out of balance loading on the hangers. Diaphragm action of the floor plates transmits lateral wind load from the perimeter cladding to the core.

The key architectural concept focuses on the relationship with the adjacent garden, originally the St John Zachary Churchyard. Accommodation is organised around an open sided south facing atrium overlooking the garden. The atrium contains the principal vertical circulation, four glass lifts reached from a series of glass floored bridge decks and the scheme extends the garden with terraced planting beds climbing up the external face of the atrium. The imaginative use of structural steel enables the southern edge of the floors to be hung, thus avoiding any ground floor columns along the garden boundary. Steel vertical braced bays around the central service core resist the overturning moments induced by the inclined hangers. Plan bracing transfers the resultant push/pull horizontal forces at first and ninth floors from the hanger node points to the central core.

The diagonal tensile rod ties that provide support for the principal structure were assessed in a detailed fire-engineering analysis to ascertain what effect an internal fire would have on the stability of the structure. The initial assessment was based on the ratio of energy input from the fire to the mass of the hanger available to absorb the energy. To determine the performance of the hanger more accurately, assessors calculated the temperature of the environment to which a tension rod was likely to be exposed in a fire. Taking account of the thermal properties of the steel, the temperature of the fire and the duration of exposure, it was possible to calculate the peak temperature achieved by the hanger.

Temporary props supporting the first floor enabled the simultaneous construction of the suspended south bays with the main frame up to the hanger connection nodes at the ninth floor. Hydraulic jacks lifting the hangers transferred the load from the temporary props to the inclined hangers. Tension to the hangers was applied progressively, in pairs to control distortion sway on the structure. The measured movements were continually checked against the predicted theoretical values, determined from the detailed analysis of the frame and the tolerance allowances of the cladding assembly.

Judges’ Comment

s:

This imaginative multi-storey steel framework has admirably accommodated the architecture, sunken garden and Roman archaeology in this City of London site. The attention that has been given to the relationship of this building with its external environment is clear to see, and very well done.

Hampden Gurney School, London

Hampden Gurney School, London

Architects

Building Design Partnership

Structural Engineer

Building Design Partnership

Structural Contractor

Premier Structures Ltd

Main Contractor

Jarvis Construction Ltd

Client

Hampden Gurney School

BDP has broken the mould of inner city education buildings with Hampden Gurney School. In contrast to the single-storey schools often found in the densest parts of our cities, BDP has designed a multi-level primary school that creates the corner piece of a Marylebone city block in London.

The project includes two new six-storey apartment blocks on each side, the profits from which funded the redevelopment of the school.

Classrooms are set on three levels above ground floor and there is a technology teaching room on the roof. Children “move up” the school from nursery level at the ground floor. Play decks, located at each level of teaching, are separated from the classrooms by bridges across the central atrium. The decks provide safe, weatherproof play for different age groups adjacent to their classrooms as well as the prospect of open-air classrooms on warm days. The hall, chapel and music and drama room are set at the lower ground level.

The structural concept responds to two key aspects of the Client’s brief – the need for a flexible space for sports, dining and worship at lower ground level and strict programme constraints linked to term times and phased transfer.

The steel framed structure has an innovative roof truss that suspends the centre of the building to create the 16m clear span at lower ground level – the truss picks up the loads by means of Macalloy steel hangers connected to each floor at mid-span. Only when one enters the basement does the structural concept become apparent. The column free area creates a flexible space at lower ground level offering a host of possibilities for play, worship and performance. The steel bow arch is visible on the roof – a lightweight tensile PTFE canopy springs from the truss, protecting the atrium below and creating a sheltered and inspirational space for environmental learning and experimentation.

BDP designed the structure for simple and fast construction – the entire steel frame was erected on temporary columns. Macalloy hangers were then installed and tensioned, transferring load from the temporary columns into the roof truss. The structure was simply lifted off the temporary compression columns when the load transfer was complete, allowing easy removal of the temporary columns.

Sustainability was considered throughout the design process. BDP ‘designed in’ demountablilty of the structure – steel columns could be inserted in the hanger positions and, after load take up, the building could be demounted in a traditional way. Also, the play areas are open to the fresh air and the long side of each is curved to the south to enjoy all day sun. The central atrium provides cross ventilation to the naturally ventilated classrooms.

The construction budget for the school was £6m. The structural frame comprised 200 tonnes of steelwork and the average cost of the primary frame was £1,000 per tonne and of the arch £2,000 per tonne.

Judges’ Comment

s:

This novel structure pioneers the way to optimise the use of land set aside for educational purposes in inner city conurbations by adopting the concept of the vertical primary school. Steel and composite construction are used efficiently and effectively to provide a large column-free space at ground level for sport, assembly and other collective activities, whilst the upper floors, suspended from the bow arch and at roof level, accommodate teaching facilities for each of the class groups as they progress upwards to the completion of their primary education.

Kinnaird House, 1-2 Pall Mall East, London

Kinnaird House, 1-2 Pall Mall East, London

Architect

Trehearne Architects

Structural Engineer

WSP Cantor Seinuk

Structural Contractor

Bourne Steel Ltd

Main Contractor

Kier Build Ltd

Client

Haslemere Estates Management Ltd and Schildvink bv

Kinnaird House was constructed in the early 1920s on an island site. It was built using Portland stone held in place by an integral steel frame.

Steel and stone were tied together with mortar, brick and concrete with rubble fill in places. The original floors were constructed using riveted steel plated beams with concrete and hollow clay pots and a floating timber floor.

The client’s main criterion for the redevelopment was that the existing character of the building should be maintained while maximising the net lettable floor area. This was achieved by retaining all four facades and reconstructing the internal floors. Careful investigation proved that the existing perimeter stanchions and foundations could remain unaltered. Re-using the majority of the original foundations also produced a design that did not affect the Bakerloo Line running tunnels that cross directly below one corner of the building.

Several studies were undertaken in the initial stages of the project to determine the position of the core and the number of columns within the building. With careful planning and optimising of the beam spans and services locations it proved possible to reduce the total number of internal columns to just four, giving the client excellent floor space. The adoption of a slimflor beam system and lightweight concrete metal deck floor slabs and the consequent reduction in load carried by the foundations enabled an additional floor to be inserted into the old banking hall area and an extra floor to be added for plant at roof level.

New angle brackets were welded to the existing stanchions during the demolition phase to assist in the erection of the steelwork frame. This simple procedure greatly assisted the following main-frame erection process and contributed to safe and efficient work on site.

Where appropriate, re-cycled materials were specified. In effect, the original embedded steelwork was re-cycled by its re-use in the new load-carrying frame. Trehearne Architects’ proposal was based on a design that would provide an environmentally friendly building with maximum net lettable area and fully integrated mechanical and electrical services. By carefully selecting the level of the first floor steelwork it was possible to use the existing full height ground floor windows to naturally light ground and first floor without affecting the external facade.

The newly refurbished building achieved an ‘excellent’ rating under the Building Research Establishment Environmental Assessment Method (BREEAM). This is uncommon for a refurbished air-conditioned building in central London.

The key features of the building are the use of simple slimflor beam construction and lightweight concrete on metal decking floor slabs and the connection of the new internal steelwork frame to the original embedded steelwork stanchions. The use of the slimflor construction solution also allowed an unhindered services zone across each floor plate. Steelwork framing for the turrets, chimneys and vehicle entrance also shows that steelwork is a versatile material that can be used to deal with complicated geometry.

Judges’ Comment

s:

Kinnaird House represents a fine solution to the problems of inner city reconstructions, occupying a prominent site near London’s Trafalgar Square. The challenge of inserting new floors, with one additional storey, within the retained facades is a familiar one. The success in coping with the logistical problems of sequencing deliveries, new framing and reconstruction could only be achieved by the skilful use of steelwork.