Design Awards

Coal Drops Yard, London

© Hufton + Crow

Architect
Heatherwick Studio

Structural Engineer
Arup

Steelwork Contractor
Severfield

Main Contractor
BAM Construction

Client
King’s Cross Central Limited Partnership

The King’s Cross development is a visionary urban regeneration masterplan in the heart of London. Coal Drops Yard was to form a focal point within this development, a vibrant retail destination that boasted public squares, bars, restaurants, and cafés.

The development is centred around the East and West Coal Drops. These long brick buildings were originally built in the 1850s and used to distribute coal around London, which had arrived from the north of England by train. The buildings were separated by a cobbled yard space, each building consisting of a 13m-wide, 3-floored, masonry structure with repeating cross-walls at 6m. This footprint did not lend itself to the large retail units desired of the scheme. Furthermore, the East Coal Drop was protected as a Grade II listed building, the buildings had suffered fire damage, and had evidentially been left for many years, so it was clear that significant intervention was required.

These constraints led the team to reach a design solution whereby the two buildings became linked at roof level by creating a new floor that ‘floated’ over the central yard space below.

While English Heritage and Camden Council gave their permission to link the roofs via a bridge-like structure, they requested to connect the roof in a way which maintained the idea that the East and West Coal Drops were two separate entities.

This request led to the ground-breaking architectural design of the ‘kissing point’ in which the inner roofs of the East and West Coal Drops stretched toward one another and delicately touched high above the central yard. The merging of the roofs was such that visually they appeared to connect at an indefinitely small point while the floor below hung from a roof that was seemingly devoid of any significant structure.

The structural solution to the kissing point concept presented several challenges. The roof support solution had to allow the complex roof geometry to be formed whilst being supported on buildings set 33m apart. The weight of the new roof and the floating floor below had to be carried without exposing the existing heritage structure to any additional loading or deflection. The magnitude of movements experienced by the delicate architectural façade, which spanned 7m vertically between the new floor and roof, had to be limited.

As this required both high stiffness and strength in combination with limited space for new structural elements, clearly steel was the only structural material that could deliver a cost-efficient solution.

The steel structure consists of three ‘bows’ (or tied arches) that rest upon one other. The central bow spans the shortest distance between buildings and hides a steel V-shaped member within the small cladding envelope that is available at the kissing point. Hidden below the floating floor a tie carries a 20MN tension to resolve this bow. The ribbon-shaped roofs are formed by the 2nd and 3rd bows. These consist of a ribbon shaped truss complete with three chords and bracing and are supported at the northern and southern end of the Coal Drop buildings and centrally on the first bow. Their horizontal forces are resolved with a tie hidden at floor level on the inner edge of each building.

The suspended floor is hung from the leading edge of the ribbon trusses, with a series of steel hangers that connect to composite beams of the new floor. The ties and floor diaphragm resolve horizontal forces allowing new steel columns and foundations within the existing building footprint to support the vertical load of the new structure.

The roof steelwork was fabricated to a pre-set geometry to compensate for the predicted deformations under dead loads. The aim was to ensure that the new suspended floor would settle to a flat and level position at the point of completion. This required points of the roof steelwork to be fabricated up to 90mm away from their final positions.

The majority of roof steelwork was broken into large fabricated sections which were transported to site then sub-assembled before being lifted into position. The process allowed for minimum site assembly, temporary works, and working at height activities.

The roof was erected on temporary trestles with a de-propping facility incorporated at each temporary support location, which allowed the roof to be erected and bolted together in its pre-set condition, and once it was acting as a single unit, to be depropped in a controlled manner.

The project contained considerable risk given the complexity of the site and the circumstances arising from the heritage structures. However, Coal Drops Yard is not only a success story of architecture and engineering. Forming a key locale within the King’s Cross redevelopment this project has significantly contributed to the revitalisation of this once abandoned and derelict corner of London. This legacy will surely form a catalyst for change in the surrounding areas.

Judges’ comment

The kissing roof that links the two original Coal Drop buildings led to a solution of three steel bowstring frames all working together, shaped to reflect the ribbon roof. New exposed steel at deck level is extremely well integrated and carefully detailed to be in keeping with the original structure, strengthening and extending it to suit its new purpose.

Jaguar Land Rover Engine Manufacturing Centre

© Simon Kennedy

Architect
Arup

Structural Engineer
Arup

Steelwork Contractor
Severfield

Main Contractor
Interserve Construction Ltd

Client
Jaguar Land Rover

The BREEAM ‘Excellent’ Engine Manufacturing Centre comprises 165,000m2 of production space, offices, social support spaces and a community educational centre, and is an exemplar of modern sustainable manufacturing.

Innovation, collaboration and the well-being of people at the facility have shaped the success of the building. A simple layout was derived from optimum operational adjacencies and designed for flexibility, providing both an efficient process flow for manufacturing and giving staff easy access to support facilities. Naturally-lit machine and assembly halls are flanked by supporting office and ancillary buildings. This approach optimised production performance and blurred the boundaries between production and offices through visual transparency, clear movement and social spaces, helping to break down the barriers of communication between staff.

A powerful architectural impression was achieved through the simple, repeating and discretely expressed façade modules, generated by the north lights. The skylights provide generously day-lit spaces throughout the complex, and continuous strips of glass along the ground floor allow the buildings to float, further humanising the scale of the spaces while providing views out to the landscaped surroundings.

With a firm date for starting production, programme was critical. The first phase of this world-class facility was handed over just 24 months after the design team’s appointment. Subsequent phases followed in continuous sequence from 2013 to 2016.

Phase One was one of the first structures in the UK to be designed to the Eurocodes. Arup developed spreadsheets to automate member utilisation checks direct from analysis output, enabling all members to be rapidly optimised. Despite the intensive servicing loads on the roof, this reduced the roof tonnage to only 28kg/m2, which is impressively light for 30m spans.

All the structures comprise braced steel frames, with grids set by the bay sizes of the production areas below. Concept studies explored grid size with the client and compared portal action, but the braced frames were considered the cheapest solution.

The north lights are formed using the primary 30m span trusses to minimise intrusion of the structure into the production spaces and thereby minimise building height. The Machine Hall uses a grid of 30m by 15m, matching the rhythm of the north lights. Assembly Halls have a grid of 30m by 30m, at twice the rhythm of the north lights, so primary support trusses are provided below the north lights on each 30m grid to support the intermediate primary trusses. Secondary trusses are provided at 7.5m centres. These grids provide for future reconfiguring of the assembly lines.

Columns were designed assuming some rotational fixity to minimise second-order effects. This was derived from a study of potential settlement of the pads and considering the need for them to stand without temporary works during erection.

Wind behaviour on saw-tooth roofs is directional relative to the saw-tooth, but large-scale roofs behave differently to small- scale roofs. So, comparing the peak wind effects from the roof geometry with peak wind directions for the site, sheltering benefits and size factors, the uplift loads were reduced by up to 70% for most of the roof.

Mezzanine floors provide support accommodation and plant spaces, using reinforced concrete slabs constructed on profiled metal decking, providing robust fire separation for plant spaces.

Primary services within the spaces distribute at roof level supported from the roof structure. This minimised the need for trenches and steps in the ground slabs, maximising future production flexibility. The roof had to be designed accordingly for intensive servicing and high point loads.

The support and spine buildings are typically two storeys high with accommodation below and plant at first floor level to feed directly into the adjacent halls. The office building uses precast hollowcore slabs to provide an exposed thermal inertia of the soffits to assist with the natural ventilation strategy.

Jaguar Land Rover’s commitment to sustainable, low carbon, manufacturing was supported by Arup’s ability to provide integrated and innovative low-energy design solutions, resulting in one of the largest buildings to achieve BREEAM ‘Excellent’.

Sustainable measures include the UK’s largest PV installation, zero operational waste, extensive grey water recycling, day- lit spaces, naturally-ventilated offices and a pioneering ‘solar cladding’ façade system.

The north lights’ vents open to expel hot air in summer reducing extract energy. Responsive dimming controls for the lighting system help to capitalise on the generous daylighting in the space to save further energy.

The project was a trailblazer for applying level 2 BIM. The one-model approach was extended to embrace Jaguar Land Rover’s own manufacturing designers, who integrated Arup’s BIM model with their Process and Equipment 3D model to create a model of the entire facility, enabling unprecedented levels of coordination to be achieved. The model was also populated with specification and data tagging to enable adoption into Jaguar Land Rover’s facilities management system.

The structural model was produced directly from the analysis model, exported to Tekla, saving the steelwork contractor weeks of modelling.

Judges’ Comment

Drawing on traditional industrial forms, the team has updated these principles to deliver a stunning workplace to train and attract the best talent in the industry. The lightness of the framing, extensive roof-lights and perimeter windows deliver high levels of natural light. The steel is efficiently designed for current operations and adaptation for changes in engine design and technology.

LSQ London

Architect
make

Structural Engineer
Waterman Structures

Steelwork Contractor
Bourne Steel Ltd

Main Contractor
Multiplex Construction Europe Ltd

Client
Linseed Assets Ltd

LSQ London is a Grade II listed building refurbishment, which required over 2,000 tonnes of structural steel and metal decking to be installed within what is thought to be Europe’s largest retained façade. Situated in London’s busiest tourist area, this project required meticulous planning and organisation to ensure the most efficient use of time and craneage without bringing the surrounding streets to a standstill.

The completed building was erected to the required tolerance of 15mm over the full height, making this project challenging for the engineering and delivery teams, but was completed on time, to budget and to the client’s satisfaction.

The existing building envelope is partially retained with new upper storeys of commercial floor space being provided. The design delivers two basements, two floors of retail space and seven floors of high quality office space with a new entrance on Whitcomb Street. Upper floors are enclosed by a new curved mansard roof. On the lower floors, new retail space has created active frontages at street level with new, clearly defined entrances.

The contemporary roof design is supported by a structural steel-framed central core and new perimeter stanchions, with complete column-free office space and spans of up to 12m providing very efficient floor space to appropriate market standards.

A new two-storey basement was created by the installation of a secant piled wall inside the retained façade profile. Shallow floor construction was used for the B1 and ground floor slabs to maximise headroom in below ground spaces, whilst minimising excavation depths.

The project was designed using Revit 3D modelling techniques to capture the integration and interfaces of both architecture and building services. This assisted the design and construction activities, but also provides full integrated models for future use.

The design of the building naturally leant itself to using steel for the primary structural elements. The design of the new steel structure introduced a new central core, and enabled clear, open-plan floorplates improving the office spaces within the building. One of the key aspects of the façade retention scheme was the alignment of new floors with existing window openings. This was assisted by integrating the suspended services within the structural downstand beam zone, such that the depth of floor zone against the façade was minimised. The use of a steel frame offered the flexibility needed to suit the various interfaces that occur with the existing façade.

The steel-framed façade dates from the 1920s and 1930s, however some areas were added during the 1960s. The steel columns are all encased in Portland stone and consequently in good condition. However, steelwork originating from various decades required extensive laboratory tests to determine its make-up and suitability prior to making the welded connections for 250 new façade retention brackets. This demonstrates the adaptability of steel-framed structures both old and new.

The new fifth floor is clad with Portland stone to integrate with the retained façade below. This floor level’s steelwork is topped with a ring beam that goes around the entire perimeter of the building.

The ring beam is formed from jumbo box sections measuring 650mm × 450mm with a 25mm thickness. The sections were brought to site in 3.5m long sections each weighing three tonnes. The box section ring beam performs two functions, one is to support the columns for the feature roof as these are not aligned with the main columns for the rest of the building, and the second function is for the stone cladding panels for the sixth floor as they are hung from the beam.

The steel feature roof slopes outwards from the two centrally positioned cores and is formed with a cranked steel frame, which in turn supports a lightweight aluminium frame and glazing. This new and elegant curved mansard roof encloses the building and offers a modern interpretation of the traditional mansard style where arch geometry sits atop a classical base. This respectful, contemporary addition to the building composition reduces the existing top-heavy visual mass of the building and, with the curved design, also seeks to ensure the building blends in seamlessly with the surrounding iconic buildings of Leicester Square.

Judges’ Comment

The use of structural steel for the new internal structure, including cores, enabled new clear-span floorplates to be achieved, whilst respecting the existing listed façade. It minimised disruption during construction in London’s busiest tourist area.

With its graceful three-storey ‘top-knot’, the building has a new lease of life as a striking yet respectful landmark in the West End.

This project showcases the role steelwork can play in the extension and re-purposing of historic buildings.

Thames Tower Redevelopment, Reading

Thames Tower Redevelopment

Architect
dn-a

Structural Engineer
Peter Brett Associates LLP

Steelwork Contractor
Shipley Structures Ltd

Main Contractor
Bowmer and Kirkland Ltd

Client
Landid Property Holdings Ltd

Located in the heart of Reading town centre, the existing Thames Tower concrete office block has been given a new lease of life with an enlarged footprint at each floor level in conjunction with a five-storey steel- framed extension above level 11.

The original scheme concept was to demolish the existing concrete-framed structure and replace it with a new 25- storey high tower, which would have necessitated the requirement for new supporting/up-rated concrete foundations.

However, through an innovative design proposal, the core of the existing structure was maintained and developed using a series of strengthening works throughout the height of the concrete frame, along with the provision of four additional steel- framed office floors to increase the nett usable internal areas. This also provided huge ‘value-engineering’ savings to the scheme as the basic core of the structure was maintained and no amendments or enhancements of the existing concrete foundations were necessary.

The refurbishment works included stripping the building back to its structural frame and the removal of the existing concrete cladding panels to all elevations, which were then replaced with a new terracotta tiling system to complement the local town centre surroundings.

In order to accommodate the increased dead and imposed loads from the new five-storey extension between levels 11 to 16, it was necessary to strengthen the columns and floors of the existing concrete-framed structure. This was achieved by the following:

  1. The supply and installation of 15mm thick stiffening plates to the full width of the concrete columns between levels 6 and 11. The columns were initially ultrasonically scanned to avoid clashes with the steel reinforcing bars. Following the bespoke fabrication of each of the 282no individual stiffening plates, these were fixed to the columns by means of 14no resin anchor bolts and subsequently bonded to the concrete face across the full plate area using a special ‘fast-curing’ resin.
  2. These were further complemented by fabricated ‘cruciform’ stiffening brackets at the column heads, in order to adequately disperse the upper load transfer.

An intermediate mezzanine steel-decked floor was also supplied and incorporated at level 01, using cellular beams to provide a lightweight steel solution with maximum integrated space for M&E equipment.

The above strengthening works, along with further stiffening plates and brackets at level 11, also facilitated the use of a roof- mounted tower crane for the installation of the new upper five-storey extension. The tower crane was installed approximately halfway through the steel site programme. Initially all of the internal steel members for the strengthening works had to be hoisted through the existing internal lift cores and ‘hand-balled’ into position.

The structure’s original design had the perimeter columns protruding beyond the main floor areas, along with splayed 45 degree corners throughout its full height.

As part of the building refurbishment, and to maximise the internal floor areas, the new design introduced a series of additional perimeter support beams which were connected to the external edge of the existing concrete columns. Metal decking and associated concrete floor infills then created an increase to the building footprint up to the exterior face of the perimeter columns.

The four corners of the building were also altered to create a now perfectly square structure, which has further increased each of the tower’s existing commercial floorplates. This was achieved by installing a new steel column to each of the building’s corners with secondary infill framing. These triangular corner infills were then subsequently metal-decked and concreted throughout the full height of the building. This has increased the tower’s floor space from 13,600m2 to approximately 17,000m2 of offices and 740m2 of restaurant/café space.

The new upper steelwork extension is connected to the existing concrete columns at the newly created level 11 and corner infill sections. Predominantly based around a 6.3m x 5.8m internal grid to match the existing columns below, each floor is formed with a series of cellular beams that accommodate services and support a metal deck flooring system.

The use of composite cellular beams has kept the steel weight to an absolute minimum, thus limiting the additional dead load on the existing structure below, and ultimately allowing M&E services to be distributed within the structural depth of the new steel members at all levels.

Due to limited storage space on site, vehicular restrictions on member lengths and the need to minimise the weight of mechanical plant on the roof structures, it was necessary to construct the upper extension on a floor-by-floor basis.

This was sequentially constructed by means of the primary steel frame, followed by the metal deck flooring and associated concrete topping at each level. Following the adequate curing of the concrete deck at each level, the next level was subsequently constructed, up to level 15.

The steelwork for the new floors up to level 16 was completed in December 2015.

Judges’ Comment

This is a thorough and rigorous project which has been carried out with ingenuity and skill. With both painstaking analysis and inventive thought, a substantial but unloved city-centre concrete building has been enlarged upwards and horizontally by the creative use of steelwork.

The project was technically and logistically challenging, but teamwork and a committed client have achieved a solution which is exemplary in its calm elegance.

First World War Galleries, Imperial War Museum, London

Imperial War Museum 1

Architect
Foster + Partners

Structural Engineer
BuroHappold Engineering

Steelwork Contractor
Bourne Steel Ltd

Main Contractor
Lend Lease

Client
The Trustees of the Imperial War Museum

The Imperial War Museum (IWM) was founded in 1917 and moved to the site in Lambeth on 7 July 1936. Since then it has been refurbished on numerous occasions over its history.

On 19 July 2014 – to mark the start of the Centenary of the First World War – a transformed IWM London re-opened with groundbreaking new First World War Galleries and a dramatic new atrium displaying iconic large objects and terraces featuring key stories from the museum collections.

Refurbishment of this heritage building uses structural steelwork once again to reinvigorate this British national museum. IWM London’s atrium houses rockets, planes, tanks and other military hardware as a reminder of the weapons of war developed to protect the nation in times of conflict.

The refurbishment project required the cutting-out and removal of existing concrete floors and steelwork to create an extended atrium space for the large hanging exhibits. The removal of all materials and the introduction of new materials inside the enclosed atrium area was through the constraints of the existing entrance and access ways, and often material was manhandled when mechanical means was not possible. The access way into the main atrium was complicated by having a 90 degree turn from the access way between the existing concrete columns and the atrium space. This limited the new steelwork to a maximum length of approximately 8m. Trusses, stair frames, link bridges and long columns all had to be spliced to get them in the building, which also meant substantial temporary support frames were needed to erect the individual pieces.

To add to the challenges, the project commenced before the museum underwent a temporary closure period to allow for the most invasive works to be completed.

Therefore, removal of the existing hanging exhibits from the barrel vault roof and the survey of the existing structure had to be carried out simultaneously as night-time working.

Twenty tapered Vierendeel columns connect back to the existing steel frame, holding up a high level flying steel exhibition gallery including trusses and floor beams, above which sits the magnificent retained barrel vault steel roof structure. These new intricate column structures now support the fair-faced precast concrete cladding, as well as the hung exhibits, to complete a crisp structural elevation to the atrium space. Floating steel staircase structures, infill floor structures to match and extend the existing floors, a corridor structure in the existing loading bay and two new lift structures with a triangular truss link bridge to the high level flying gallery complete this 370t of new structural steelwork on the five storey internal structure, all of which had to match the existing floor levels.

The majority of the steelwork was finished with intumescent paint, with areas that are visible in the final condition being matched to the finish of the existing steelwork. The feature stair structure up to the link bridge was finished with a hot zinc spray sealed with a renaissance wax to the underside of the trusses and treads. The top of the treads were covered with a precast concrete nosing sat on the steel plates and the side trusses were finished with thin steel sheet wrapped tightly around the supporting steel members.

On the high level flying steel ‘Roof Terrace’, there were 12 specialist lifting lugs welded to the underside of the trusses and beams to support the aircraft hung from the flying gallery.

The erection of the high level flying steel required a load transfer operation to remove the existing columns supporting the barrel vault glazed end gable which was to be supported by the high level flying steel truss. The barrel vault glazing remained in place throughout the construction, so there could be no movement of the existing structure during the load transfer.

Due to the tight confines of the atrium area, the steel construction process had to be coordinated with numerous other trades to enable the final structure to come together.

HRH the Duke of Cambridge and the Prime Minister, David Cameron MP, officially opened the IWM London’s new First World War Galleries following the refurbishment in July 2014.

Judges’ Comment

A dramatic new atrium has been built within the transformed museum. Angular and robust structures frame new galleries and support war machines in a cathedral-like space. Steel construction uniquely allowed constraints of access and time to be well-answered. The visitor route is now clear and exciting.

A strong sign of success is that visitor numbers have doubled in the year.

Tombola HQ, Sunderland

Architect
Ryder Architecture

Structural Engineer
s h e d

Main Contractor
Brims Construction Ltd

Client
Tombola

Online gaming giant Tombola’s new headquarters building is an important element of their business plan for future growth and international expansion. Designed to attract and retain the best talent from the region and further afield, the building is key to their desire to double the size of their tech team by 2020. By providing a stimulating, attractive working environment, it will help resist the lure of larger centres like London and California, keep jobs in the region and boost the local economy. Beyond that, the building also raises the bar and sets a new standard for the 21st Century workplace environment for other employers to match by investing in higher quality working environments.

The new £7m building at Wylam Wharf in Sunderland stands next to the company’s existing headquarters, which is a former bonded warehouse dating from the late 1700s, within a conservation area, on the banks of the River Wear.

The 2,485m2 modern addition creates a riverside campus feel that incorporates both the old and new buildings as well as a new riverside courtyard created between the two. The scale of the new building, its multiple pitch roof and brick construction reflects the warehouses which characterise this section of the riverside.

Modern and technologically advanced open-plan offices for approximately 160 staff occupy the first and second floors, and a three-storey high atrium floods natural light throughout the glazed building. The ground floor includes a reception area, a bistro and gym for employees with bleacher style stairs leading to the modern openplan upper floors. The stunning 15m-high atrium with wide bleacher steps and 15m² video wall opposite, delivers a real ‘wow’ factor for all visitors and provides an amazing open space for meetings. The building also boasts a diverse range of informal training / presentation suites with the latest AV / video conferencing technology.

From the outset, Tombola wanted to create a working environment attractive to young professionals, an address with a historic industrial location and a campus hub for the activity that an ever-growing and busy tech firm generates daily. The resulting building provides an environment that encourages harmony with a workplace culture of informality and flexibility. Agile workspaces within the open-plan and airy environment, supported by strategically located private meeting rooms, enable closer collaboration with other teams with the removal of the physical barriers that existed in the old building. The new space facilitates more idea sharing, more communication, and more organic interactions.

Tombola HQ is a unique structural solution combining all three main design disciplines in one solution, architecture, M&E and structure. The exposed steel frame has been aesthetically detailed to a high standard rarely seen on commercial projects, with the additional integration of heating and cooling being cast in and monolithic with the exposed concrete slabs. Great care was taken through significant collaboration performed to ensure that all the elements worked seamlessly together. The steel frame is braced but also has moment frames, set-back columns on the northern edge to create the dramatic building overhang and cantilevers to form the full-height glazed eastern façade.

The office floorplates are clear span with exposed concrete soffits providing radiant heating and cooling. To allow the floors to appear to float and the fenestration to span fully to the soffits, all supporting beams are detailed as Rectangular Hollow Sections (RHS) with projecting plates welded to the bottom flange to carry the 250mm thick precast concrete floor slabs. The main columns are structural hollow sections too and this keeps their size to a minimum and continues the sleek lines of the building from the horizontal to the vertical. The RHS edge floor beams also support the brickwork façade thus providing a solution that is very efficient in terms of member numbers.

The roof appears to float which is made possible by utilising a moment frame. All the UC section rafters are within a shallow construction zone, with purlins within the depth of the UCs, and no horizontal ties. The structure-free rooflights provide unobstructed views of the dramatic skies.

The central atrium again is structure-free and provides an open-plan flexible-use area for the staff for collaboration and sharing collective inspiration. The AV and fire alarm systems are hidden within the hollow section structure, using them as containment systems to keep the sleek and uninterrupted finish.

Overall the building could not have been delivered in its amazing form without using a steel-framed superstructure. It has created a stylish and laid-back working environment that is completely in harmony with a culture of modern informality and flexibility. It’s the ideal workplace for smart software developers, wanting to build long-term careers and a great working environment for collaboration and innovation. The subtleties have to be seen to be appreciated with this truly spectacular setting granted a calibre of building it deserved.

Judges’ comment

This project exemplifies how, with a dedicated client and a top-class team, structural steel can produce cost-effective yet beautiful results that are much loved by its users. Through simple yet sophisticated design and rigorous attention to detail, this wonderful headquarters building exhibits exceptional quality and value. It is a clear Award winner.

V&A’s Exhibition Road Quarter, London

© Paul Carstairs/Arup

Architect
AL_A

Structural Engineer
Arup

Steelwork Contractor
Bourne Steel Ltd

Main Contractor
Wates Construction

Client
Trustees of the V&A

The most significant intervention undertaken at the V&A’s South Kensington campus for over 100 years, this major development provides a large column-free underground exhibition gallery with an oculus to allow the influx of natural daylight, an open courtyard and significantly improved street level entrance from Exhibition Road into the Museum.

The courtyard also acts as a venue for installations and events and is served by a glass-fronted café.

The Sainsbury Gallery, a new 1,100m2 column-free space, will be one of the largest temporary exhibition spaces in the UK and allow the V&A to significantly improve the way it designs and presents its world-class exhibition programme.

Entry to the new Sackler Courtyard will be through the arches of the 19th Century screen designed by Sir Aston Webb.

From the courtyard, and from key internal locations through the glazed skylights, it is now possible to see previously hidden façades of the museum’s original buildings, including the detailed sgraffito decoration on the Henry Cole Wing which has been revealed to the public for the first time since 1873.

Following an extensive international competition Amanda Levete Architects (AL_A), working with Arup, were appointed as the designers of this scheme. Key to the success of the competition was the use of structural steelwork for the concept design for the ‘folded plate roof’, a system of triangular steel trusses which span 38m across the gallery, support the courtyard, café, and crucially allow the changes of existing ground levels to be fully exploited to fit in a mezzanine floor. As well as the significant vertical loads that this structure supports, it is also resisting significant prop forces as it is the ground level structure of a 15m deep basement.

During the excavation of the basement, 800 tonnes of historic Grade I listed stonework stood on one ‘mega-beam’ formed of four individual steel beams. The ‘mega-beam’ was temporarily supported on steel needles, which were then replaced by four steel columns.

The beams and columns are expressed within the volume of the stairwell, so that as visitors pass from the entrance to the gallery they understand how the façade above is supported, and where they are in relation to the rest of the museum.

The ‘folded plate’ structure comprises 13 ‘Toblerone’ trusses supported on an inclined storey-height mezzanine truss. Through optimising both the overall geometry and the geometry of the members making up the trusses, the design team was able to save 40% of the steel weight of the initial concept. Early engagement by Arup with Bourne, and the steel industry, during the design process meant that the design moved from needing extensive temporary support to erect it to one where the ‘Toblerones’ were self-stable for ease of erection.

Bourne was responsible for the connection design, fabrication and erection of the 13 ‘Toblerone’ trusses, each up to 25m in length and weighing up to 14 tonnes. Transporting and delivering these trusses in London was a logistical minefield requiring careful planning and coordination with Highways England.

The unique geometry of each truss and the difficulty in positioning meant that the fabrication had to be precise in its execution. Due to the geometry and sheer size of the trusses, bespoke jigs needed to be made to aid fabrication, and much of the fabrication needed to be carried out with the use of mobile elevating working platforms (MEWPs).

The form of the structure presented several difficulties for the connection designers, with a combination of heavily loaded and multi-planar joints, nearly all of which were unique, with often a restricted envelope within which to achieve a viable connection. The connection designs had to incorporate allowances for erection and fabrication tolerances. The triangular trusses, which form the principal members of the roof, are an example of the geometric challenges encountered with typically two chord members and four internals intersecting at a point, with none of the members in a common plane, and the remaining members clashing well before they reached the intended connection zone.

Precision checks offsite and on-site showed that exceptional tolerances were achieved, which meant that each of the trusses was dropped into place on time, first time, every time.

The truss geometry and phasing were coordinated in an integrated 3D model between Wates and Bourne to ensure that there were no clashes between the steelwork and the heavy temporary props that laterally restrained the retaining walls before completion of the courtyard structure.

What had been viewed as a high-risk package due to the complex geometry of the steelwork, the critical structural performance requirements and the multiple challenging interfaces between it and follow-on trades, was delivered to an outstanding quality and attention to all details by a committed design, fabrication and site team.

Judges’ Comment

The inverted ‘Toblerone’ shaped trusses form a neat arrangement to support a new public courtyard and entry from Exhibition Road above new basement level galleries. This array of steelwork was hugely refined through the design process to maximise the efficiency of each member. Good use of light and colour for wayfinding in the new extension is exemplified by the striking red steel columns that so appealed to the judges.

HGV Egress Ramp, Selfridges, London

© Kevin Sansbury 2015

Architect
Gensler

Structural Engineer
Expedition Engineering

Steelwork Contractor
William Hare

Main Contractors
Blue Sky Building and SRM JV

Client
Selfridges

The Duke Street phase of the redevelopment project included forming a new staff entrance into the building below Edwards Mews and realignment of the HGV entrance ramp to the loading bays. However, the primary feature of the first phase of works was the insertion of a new 50m long 165 tonne steel-framed bridge structure, through the existing store, to improve HGV egress from the basement loading bays. This new structure is a braced steel tube linking the loading bay within the basement to Duke Street.

The structural works were designed to keep the loading bay active throughout the works, while staff access was maintained and retail operations continued within 1m to 2m of the structural works.

Design and execution of the structural interventions was made more complex by the limited existing building information, and numerous historical alterations that were discovered during the build, requiring modifications to be made to the new construction as it progressed on-site.

To maximise retail space for the client, the preferred routing of the egress ramp was tight to the perimeter of the building. This routing allowed the ramp to be partially supported on the existing steel structure, but necessitated the partial removal of three existing columns that then had to be re-supported on bespoke steel transfer girders integrated into the new ramp structure.

The routing of the ramp meant it would span over an occupied three-storey basement. To minimise disruption to these basement spaces, and to minimise the need for new foundations, support was taken from the existing 1920s steel structure along the northern edge of the ramp. On the southern edge of the ramp vertical support was limited to two new columns between which a new steel truss would span. The new columns were threaded down through the existing building and supported on new hand dug pad foundations.

Reuse of the existing 1920s steel frame on the northern edge of the ramp provided an economic solution. The existing steelwork comprised of built-up riveted sections, which geometrically added complexity to the connections, formed to the existing structure. However, the existing steel proved to be of a weldable nature and so site welded connections were adopted.

Where the new ramp is supported on existing steel columns, these were checked for a change in loading and restraint condition due to the removal of the ground floor beams. Some of the columns required strengthening but, as this was governed by buckling capacity, the columns could be strengthened relatively simply via the addition of welded plates to the existing sections to increase their stiffness. The size of the strengthening plates could be easily tailored to suit constraints on site and manual installation.

To allow the ramp to connect between road level and the loading bay within the basement a large slot was cut into the existing ground floor slab. The stability of the building is likely to be provided by a combination of frame action and some contribution from the masonry infilled building cores. The unquantifiable nature of the system meant the diaphragm action of the ground floor had to be maintained. This was achieved in the temporary condition via a temporary propping arrangement, and in the permanent condition by making connections between the existing ground floor frame and new ramp. The new ramp structure was then designed to transfer any diaphragm loads back to the existing retaining wall, with steel members being tuned to provide an appropriate stiffness.

The two transfer structures used to re- support the columns above the ramp were deemed to experience vertical deflections exceeding acceptable limits for an occupied building. However, to negate the existing structure above experiencing these movements, an erection approach utilising jacking was adopted. This allowed the load from the existing column sections to be transferred into the new transfer structures in advance of the lower column sections being removed. The jacks were used to push the transfer structures down, realising the anticipated deflections before connections were made to the existing columns.

A key challenge in the construction of the new steel ramp structure was the fact that it was to be constructed within a live existing building. As the structure was to support HGV vehicles the steel forming the structure was of a scale that, although lighter than other forms of construction, could not be manhandled. The contractor team therefore developed a series of temporary works that spread the load of a spider crane across the existing suspended basement floor. The crane could then be safely driven into the space via the existing loading bay entrance without back propping through the levels below.

The creation of the new egress ramp was a highly complex piece of engineering design and construction successfully delivered by close collaboration between the whole team.

Judges’ Comment

The creation of this new egress ramp within an existing steel structure was highly complex, yet successful. A key challenge for the engineering design and construction was that the work was to be carried out in a live and busy existing building, with ongoing high-end retail operations being immediately adjacent to the work zone.

The outstanding success of this complex project was achieved through very close collaboration between the whole design and construction team.

South Stand Expansion, Etihad Stadium

Final SSDA Brochure 2007

Architect
Populous

Structural Engineer
BuroHappold Engineering

Steelwork Contractor
Severfield

Main Contractor
Laing O’Rourke

Client
Manchester City Football Club

The South Stand expansion increased the capacity of the stadium during the 2014/15 football season, adding 6,000 new seats through a third tier on the terraces and 1,500 additional seats around the pitch. An architecturally sympathetic extension of an existing catenary ringed structure was needed, which did not compromise the integrity or capacity of the structure and ensured that the existing stadium remained operational during works.

The design was technically complex as the existing roof involved a cable net structure with a tension ring, from which steel roof rafters hung. The structural integrity of the existing tension ring relies on it running around the whole circumference of the roof; therefore any modification to the roof could not affect this, even in areas where roof rafters were removed. Protection of the existing cable was vital as there was no repair procedure in place, and damage would result in replacement and potentially the closure of the stadium for two years.

Extensive design optimisation exercises were undertaken, particularly for the steel roof and the stability cores. A whole series of geometric studies evaluated the effects of different stay and mast angles, concluding with a solution to satisfy both minimum material requirements and cost.

The stability cores were formed of steel vertical brace planes with the inclusion of outrigger bracing to add efficiency and, although a solution normally adopted on tall buildings, this approach proved effective for the project. A design and costing study of the original stays, which were formed of cable, revealed that bars could be introduced for the new stays. These had marginally more erection work associated with them, but overall were a more efficient solution. Combined 3D modelling allowed the integration of all services within the structural envelope, including the late addition of increased sports lighting requirements in accordance with new regulations.

The project contains a number of highly bespoke details tuned to the complex geometries and design challenges, including the multi-stay connection at the top of the masts and column bases formed of spherically machined plates and rotational bearings, which allow the new design to accommodate differential movements between the new and existing structures.

An area of complexity centred on the temporary modes of the stadium. For typical stadium conversions an additional tier can be built behind the existing building and a new roof constructed over the existing roof, with little interaction between old works and new. This was not the case with Etihad as the roof profile and supports at the end stands extended further back behind the seating and the new upper tier would therefore project through the existing roof profile.

The ‘interim roof’ solution involved cutting and removing the existing back of the roof, acknowledging that this meant cutting into roof rafters which had significant locked-in forces from the dead loading of the roof. Significant and complex temporary works were required for the project, with the remodelling of the existing roof completed in the first closed season alongside temporary propping to allow work to proceed above the existing roof. The existing roof was removed in the second closed season to reveal the new terrace behind. The new design respects the geometry of the existing stadium and, whilst the expanded South Stand is significantly larger than the previous one, blends into the original design.

Examples of innovation include bespoke designed solutions such as spherical bearings, cable protection frames, an upper MEWP platform, intermediate roof propping, tie bar installation lifting beams to include remote release features and hidden bolted splices in the rafters. The availability of a CTL 1600 crane, the largest crane of its type in the country, significantly influenced the lifting methodology as it permitted much larger lifts, speeded up construction and reduced the need for working at height splicing components.

In terms of sustainability the project focussed on re-use and recycling, rather than demolition. The team worked exceptionally hard to retain the existing cable net that supports the stadium roof. Much of the original building was retained during construction and existing components from the building’s façade re- used. Steel and aluminium crowd ‘flood gates’ were cleaned, repaired and repainted and the existing lower tier terracing was re-used following careful detailing of the connections to the new building. The client also received a masterplan design which enables the stadium capacity to be expanded further to the absolute limit of the existing cable net, and then only at that point does the roof need to be completely replaced.

A risk assessment considered potential fire loadings throughout the building and established specific design criteria. Intumescent paint was used extensively to enable steel to be exposed to view and corrosion protection is to a high standard and specification.

The extension, completed within 16 months, was opened on the 16 August 2015 in front of a record crowd of 54,331 people.

Judges’ Comment

This is a complex project which added 6,000 seats above the roof at one end of an existing stadium. The work tested all facets of steelwork construction to their limits, including design, fabrication and construction.

A stunning testimony to all concerned and to the capabilities of steelwork which merges seamlessly into the existing structure.

Greenwich Reach Swing Bridge, London

Greenwich Reach 1

Architect
Moxon Architects

Structural Engineer
Flint & Neill Ltd

Steelwork Contractor
S H Structures Ltd

Main Contractor
Raymond Brown Construction Ltd

Client
Galliard Homes Ltd

Long planned as part of the development at Greenwich Reach, the bridge provides a valued link for residents to access public transport links and local attractions.

The bridge has a 44m cable stayed main span supported from a single mast with a central stay plane. A short 8m backspan contains a 120t counterweight to balance the structure. Two pairs of backstays support the tip of the mast laterally and longitudinally.

The structure is supported on a 3.7m diameter slewing ring bearing underneath the mast, with a set of four electric motors to drive the bridge clear of the navigation channel concealed in the machine room within the main concrete pier.

To swing the bridge across the channel, the drive motors rotate the bridge through 110 degrees. As it reaches the end of the swing, two stainless steel nose wheels engage with ramps on the west abutment to lift the nose upwards into its service position. An electrically actuated locking pin then engages to provide a nose restraint against extreme lateral loads.

Faceted planes create an elegant and visually massive backspan and reduce to a more slender main span with a central spine box supporting diagonal struts to the edge of the deck. The plated concept is continued through the main mast, where two vertical flat plates supported by diagonal stiffeners create an innovative open Vierendeel type structure. The inclined web plates create openings to the sky to lighten the appearance for maximum transparency.

Steel is crucial to ensuring that the moving span is as light as possible. By using externally painted weathering steel for closed sections, any requirement for internal inspection and maintenance has been removed.

Rolled ‘T’ section struts are used to support the edge of the deck, creating a thin edge beam and hence a slender appearance. The struts are inclined in plan and elevation to create a lightweight space truss to enhance the torsional stiffness of the deck supported by the central stay plane.

To minimise onsite welding and meet a tight construction programme, sections of the bridge were prefabricated offsite and brought to site by road. The structure was designed to facilitate easy fabrication, and the designers worked closely with the steelwork contractors to ensure an economic construction process.

The sections were craned into place in the open position before the backspan counterweights were installed and site welding completed.

The bridge provides an exciting link for pedestrians while still maintaining a thoroughfare for marine navigation.

Judges’ comment

Through simplicity of form and operation, and structural efficiency, this bridge is exemplary in its use and expression of plated steelwork. It has become a thriving route for cyclists and pedestrians, linking the new communities of Deptford Creek.

At the mouth of the Creek, this forms an effective and attractive feature of the maritime landscape of the Thames.