Design Awards: 2016: Commendation

6 Bevis Marks Roof Garden, London

Bevis Marks Roof Garden

Architect
Fletcher Priest Architects

Structural Engineer
David Dexter Associates

Steelwork Contractor
Tubecon

Main Contractor
Skanska Construction UK Ltd

Client
Bevis Marks Developments Ltd

The striking roof canopy provides all- weather protection for the 204m2 sky court. The tubular steel and fritted ETFE canopy frames views out in two directions over central London, wraps up and over the garden and extends four storeys down the face of the southwest façade in a diagrid to assist solar shading.

The structure consists of a continuous CHS diagrid frame that is supported on eight tree columns which cantilever up from the main building’s 16th floor steelwork. Additional struts extend from the ends of the cantilevered main building steelwork that act to restrain the clad sidewalls. Further supports are provided off the façade for the open mesh apron. The geometry of the structure is complex – the asymmetry of the support positions, that are set out based on the main building grid below, results in eight different tree columns and the roof diagrid is subtly pitched in four directions to generate falls.

Due to the number of site and structural constraints, the only feasible option was to fabricate and deliver the structure in individual pieces to be assembled and bolted together on site. However, in order to give a seamless appearance to the structure, it was vital that none of the bolted splice connections were visible.

The roof grid joints are fully welded connections formed with the help of CNC ‘cods-mouth’ type complex laser cuts to the ends of each CHS branch stub member. Joints in the steel diagrid were achieved using hidden ‘hand-cup’ type splices where bolted connections are formed within the tubes themselves.

The column branching nodes were formed from a series of fin plates welded around a central stub which, in turn, were slotted into CHS elements that form the branches. The final nodes were then clad in multi-curved nylon shrouds produced using 3D printing.

Trial erection offsite allowed the complex erection methodology to be verified and refined.

The canopy was fixed to the façade of the primary structure using architectural stainless steel pin connections and brackets.

The structure was initially painted offsite with a final decorative site applied coat required to achieve the perfect finish. This was quite a challenge at the top of a 16-storey building and required the use of specialist MEWPs and rope access technicians. The final finish was a faultless light metallic sheen to complement the simple elegant nature of the structure.

Judges’ Comment

The diagonal-framed steelwork and ETFE canopy is a most effective feature distinguishing this office building in a densely packed city. Challenging technical constraints were effectively resolved to provide a most desirable and popular roof garden.

Additionally, this provides an often- ignored fifth elevation of the building, as seen from the surrounding townscape heights.

Lagan Weir Pedestrian and Cycle Bridge, Belfast

Lagan Weir Pedestrian and Cycle Bridge

Architect
AECOM

Structural Engineer
AECOM

Steelwork Contractor
M Hasson & Sons Ltd

Main Contractor
Graham Construction

Client
Belfast City Council

Recognising the increasing number of users of the existing bridge connecting Donegall Quay with Queens Quay, Belfast City Council decided it was time for something wider with more capacity. After investigations on the existing ‘Pier Houses’, the decision was made that a primarily steel-framed footbridge would be most suitable for this scheme.

The overall length of the footbridge is 120m and it is curved both on plan and in elevation. The width also varies along the length up to 8m at the widest point. The total tonnage of structural steel for this project was c 270 tonnes.

One of the main challenges on this project was the need for a crane suitable to lift 25 tonne sections of the bridge deck at a reach of 70m, which resulted in a 1,000 tonne crane being used for the main bridge deck lifts.

The existing four ‘Pier Houses’ contain the controls for the daily operation of the lock gates which control the flow of the water in and out of the river Lagan. These ‘Pier Houses’ were to become the main support points for the new footbridge. The bridge is connected to them via four steel truss-type frames or ‘trees’ made from CHS sections, each of which was unique as a result of the bridge being curved in two directions.

There are nine unique deck sections, the largest being 17m long. The main framing of the deck sections were made from a combination of 610 x 229 x 101 UBs for the internal beams and 500 x 300 x 16 RHSs for the perimeter beams.

Individual bespoke 10mm thick large fin plates were welded to the RHS perimeter member to form the curved profile on plan. The deck plates are all 15mm thick and fully welded to the framing beams and act as part of the main structure.

Due to the size of the large crane it was necessary to erect all of the bridge sections as far as the halfway point from the first side before moving to the other side and repeating the process.

The completion of this bridge owes a great deal to the quality, versatility and efficiency of structural steel used with care and ingenuity. It is estimated that 16,000 people now cross this footbridge each week.

Judges’ Comment

Challenging survey, design and co-ordination were required in order for the bridge to be supported from the existing ‘Pier Houses’ that were part of Lagan Weir. The complex fabrication and erection of the support ‘trees’ and bridge deck were superbly executed by the steelwork contractor.

This beautifully finished and important bridge links the city centre and the Arena/Titanic area on the other side of the Lagan.

The Diamond Engineering Building, The University of Sheffield

The Diamond Engineering Building

Architect
Twelve Architects

Structural Engineer
Arup

Steelwork Contractor
Billington Structures Ltd

Main Contractor
Balfour Beatty

Client
The University of Sheffield

‘The Diamond’ is a new Undergraduate Engineering Facility for The University of Sheffield providing specialist engineering laboratories, lecture theatres, flexible seminar rooms, open-plan learning and social spaces, a library and café.

The building’s design is both conceptual and practical, as well as being sympathetic to the existing architecture of the area. Its name derives from its unique exterior façade of interconnected diamonds in anodised aluminium that are fitted to the exterior glass cladding.

With a BREEAM ‘Excellent’ rating the structure is environmentally efficient. The positioning of windows maximises the inflow of natural light into the laboratories, and aids ventilation without the sole reliance on air conditioning. The windows are designed to control solar gain within the building, with larger openings to the north façade and smaller panels on the south side, as well as the inclusion of well-positioned opaque panels.

The ground floor has three access points to the central atrium with full-height glazing on the north and south edges giving internal views into the specialist engineering laboratories. The glazed apertures between the higher levels allow both the roof lights and daylight to flood into the open-plan study spaces below, whilst also creating acoustic separation.

A large proportion of the structure below roof level was neither on grid nor orthogonal in set-out, but the adaptable and slender nature of steel construction lent itself to the unusual design.

The connections to the façade panels were formed using offsite shop-welded propriety studs which reduced costs significantly and saved weeks of additional construction time.

The city centre site produced several challenges and restricted access so timings for deliveries were paramount. The steel was lotted in approximately 5-10 tonne lots to arrive and be erected in numbered sequence for safety, practicality due to limited on-site storage and stability during construction. The programme also had to consider minimising the disruption to the students.

The façades had to be accessed partly from the ground and partly from the structure which resulted in numerous challenges. As such, specific MEWPs had to be selected which had a big reach but were sufficiently lightweight so as not to cause load capacity issues on certain platforms.

Numerous protection systems were specified to cater for the multitude of environmental and aesthetic requirements. Finishes provided included galvanized, zinc phosphate and multi-coloured systems to achieve those requirements whilst minimising future maintenance.

Construction work began in July 2013 and the building was successfully completed in time for the beginning of the 2015 autumn semester.

Judges’ Comment

A testament to the success of this imaginatively designed university building is how well it is used by the students. Exposed steelwork elements, including an immaculate spiral staircase, contribute to the architectural language of the interior.

This well-crafted building with its excellent internal environment is bound to inspire all who use it.

Land Rover BAR America’s Cup HQ Building, Portsmouth

Land Rover BAR Americas Cup HQ Building

Architect
HGP Architects Ltd

Structural Engineer
Reuby & Stagg Ltd

Steelwork Contractor
T A Colbourne Ltd

Main Contractor
Allied Developments Ltd

Client
Land Rover BAR

The new Headquarters Building provides the manufacturing facility for the highly sophisticated racing boats, as well as the ancillary facilities necessary to support the bid to host the America’s Cup Challenge in 2021. It was also a requirement to provide a visitor centre for the involvement of the local community.

The ground floor footprint and storey height is dictated by the requirements of the manufacturing process. The architect has avoided producing a slab sided box by adopting a plan shape with the north and south elevations tapering to the curved eastern elevation, whilst the western end provides the access to the three manufacturing bays. In order to reduce the mass of the building each of the upper floorplates at first, second and third levels is of a different size and shape to the one below, providing large external terraces at each level.

A fabric façade resembling sails wraps around part of the elevations which, as well as providing architectural interest, serves the practical purpose of providing solar shading and a wind barrier, enabling natural ventilation even on days with high wind speeds.

The programme to deliver the building was extremely short with a lead-in time of only around 3.5 months from architects’ pre-planning concept stage to commencing construction. Hence it was essential that as much of the building structure as possible should be manufactured offsite and delivered on an ‘as required’ basis.

The large clear span floor areas, some of which act as transfer structures, and the requirement to provide up to four overhead electric cranes within the ground floor area meant that the most economical solution would be a structural steel superstructure. This choice of frame material also had the advantage of minimising foundation loads as, due to below ground obstructions, pile diameters and locations were restricted.

At an early stage it was agreed to use composite cellular beams for the floor construction to accommodate services and allow flexibility in their distribution. During the design phase an area of mezzanine was added which, due to the span and limited headroom, could not be supported by a floor beam. A Vierendeel truss was introduced at high level on the line of a glazed screen and the mezzanine hung from the truss. The use of 3D modelling enabled all the various changes to be incorporated and allowed the fabrication and erection to proceed within the agreed time frame.

Despite the extremely tight programme involved the project was successfully handed over to the client on time.

Judges’ Comment

The world of ocean racing is extremely highly pressurised, hence this critical building project faced very tight timetabling and last-minute client requirements. Encompassing industrial, commercial and public spaces has required varied forms of steelwork, from long-span lattice girders to well-detailed exposed structure in open areas.

The team worked closely and effectively to produce a striking building and satisfy the client and public.