Design Awards

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.

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.

Bloomberg London

© Aaron Hargreaves/Foster + Partners

Architect
Foster + Partners

Structural Engineer
AKT II

Steelwork Contractor
William Hare

Main Contractor
Sir Robert McAlpine

Client
Bloomberg

Bloomberg London represents one of the largest, most notable developments to shape the post-Olympic landscape of London. Bloomberg’s new European headquarters is respectful of its location in the heart of the City of London, close to the Bank of England, St Paul’s Cathedral and the church of St Stephen’s Walbrook. It is a true exemplar of sustainable development, with a BREEAM ‘Outstanding’ rating – the highest design-stage score ever achieved by any major office development in the UK.

The architect’s vision consisted of two adjacent 10-storey buildings with a pedestrian access path cutting diagonally through. A steel frame with composite concrete floors is clad with sandstone and metal fins to produce a solid, understated elegance set to last within a hostile city environment.

The structure’s sensitive island location meant that physical limitations were set by the adjacent roads, as well as the remains of London Wall running close by. Constructing close to an existing sewer, the adjacent Waterloo & City line tunnel and the new direct link to Bank Underground station all required third party agreements and considerably affected programming. In two such immensely complex 10-storey structures adding value through design has been key, and AKT II was able to do this from the basement upwards. The location was previously home to Bucklersbury House, a disused 1950s structure demolished prior to start on-site. However, the slab-and-pile foundations were retained following a radar survey which confirmed that the vast majority could remain, with additional piles introduced only in the south-west corner.

On plan, the form and setting out of the north and south buildings respond to the angular nature of the site and the alignment of the new arcade with Watling Street. To achieve this both buildings use a unique structural grid set out on a 13.85m equilateral triangle that maximises open floorplates. The form of construction is similar to that found in orthogonal steel- framed City office buildings. All cores are formed from insitu reinforced concrete but, in contrast to traditional building forms, have been pushed to the perimeter to increase the extent of uninterrupted floor space and improve visual connectivity. To further enhance this, lift shafts have been opened up to animate the façade and act as light wells. The two buildings are also connected at high level with a series of link bridges above the arcade. The scale and precision of the stone and bronze façade is achieved with an independent primary frame which connects to the main columns and eliminates the larger movements in traditional edge beam solutions.

The structural grid is interrupted in several locations with transfer structures to create the unique spaces within the building. The most significant of these occurs above the pantry level which involves a storey deep truss within the level 9 plant floor spanning up to 26m between columns. This allows the suspension of level 8 and the removal of four main internal columns to create a two-storey high vast communal space within the pantry with spectacular views of St Paul’s Cathedral.

Within the centre of the north building is the feature ramp which provides access between floors from level 2 to level 8. The steel ramp structure is 1.5m wide and spans 30m between floors measured along its centreline. The elliptical oculus within the floorplates through which the ramp passes also rotates 120 degrees at each floor level following the plan transcribed by the ramp.

The main reception carves a column-free space under the ramp between ground and level 2, introducing a three-dimensional structural vortex form that spans, displays, announces and integrates architecture and structure for a spectacular experience before revealing the ramp as a structural force majeure.

The benefits of using steel construction for Bloomberg London included providing long-span uninterrupted floorplates and small structural zones relative to the span, with fully integrated services within the structural depth. Complex transfer structures could be incorporated within the building, saving space when compared with other materials. The project showcased skill and workmanship through the creativity of the devised structural solutions that achieved architectural design intent within this modern office environment. Stability was provided to the north and south 10-storey steel-framed buildings by concrete cores which were on the perimeter of the buildings.

The peak site of erection was the north and south buildings running in parallel with each other, which required approximately 600 tonnes of steelwork to be produced per week.

Thanks to 4D BIM planning and offsite manufacture on-site risks were reduced, William Hare worked with the project team to ensure delivery was on time and error free.

Judges’ Comment

The elegant exterior of this major building, a polite addition to the City, conceals a fabulous interior supported by a highly innovative design in steel. The unique triangular column grid and roof transfer system create the large open spaces required by the client, whilst the vortex transfer structure and atrium ramp produce effective yet stimulating circulation routes. The attention to detail throughout the project sets the highest standard for commercial office accommodation.

Oriam, Heriot-Watt University, Edinburgh

© Reiach and Hall Architects

Architect
Reiach and Hall Architects

Structural Engineer
Engenuiti

Steelwork Contractor
J & D Pierce (Contracts) Ltd

Main Contractor
Bowmer & Kirkland

Client
Heriot-Watt University

Oriam, Scotland’s new Sports Performance Centre, comprises a full size indoor 3G synthetic pitch for football and rugby with spectator seating for 500 people, a nine- court sports hall, a 100-station fitness suite, as well as a high performance wing that includes areas for hydrotherapy, strength and conditioning, rehabilitation, offices and a classroom.

Oriam presented truly fantastic opportunities to be creative. With long spans and a simple but elegant diagram, the cross section forms the principal structural concept. Steel arches at 7m centres span over the football hall and sports hall from buttresses on each side onto a central street of piers.

The arch profile for the football hall roof offers a high rise : span ratio and considerable curvature, giving rise to a highly efficient structure with a comparatively low overall weight. The arch is a naturally efficient form allowing the structure to work primarily as axially loaded, with relatively small bending moments generated.

Tensioned PVC fabric was chosen to clad the football hall roof as it offered the necessary light transmission properties so as to limit the need for artificial lighting of the pitch space, whilst managing heat gain. It was also preferable in the structural design, given that the fabric is lightweight and forgiving to structural movements and deflections. The diagonal arrangement of arched secondary CHS members ensured that the fabric shape could be prevented from flattening under heavy imposed loading, whilst also creating interest to the roof form itself.

The sports hall roof comprises steel arches on a 7m grid, with straight secondary steel members spanning between the arches, and curved tertiary steel members spanning between secondary beams to provide intermediate support for the roof cladding. In this case, the original trapezoidal section was re-engineered to work as a standard UB section, further increasing the material and prefabrication savings.

Central piers support the ends of the football hall and sports hall arches, which converge at a single point behind the listed wall in an area known as the Street. Initially these piers were conceived as reinforced concrete elements. However, the overall programme advantages of bringing this element within the steel package were explored and, following this review, the steelwork option was selected giving both programme and cost advantages.

The roof structure acts as an umbrella over the public fitness area and high performance wing, which are both constructed as conventional steel-framed structures and accommodate the high performance spaces and the public fitness suite, café and accommodation. In the public area the tight limitations on available floor depths meant that cellular floor beams were needed to span the full width of the structure without intermediate columns, leaving the gym and café spaces completely column-free. The same was needed in the high performance wing in order to maximise the column grid spacing and minimise the disruption to the floor layouts.

The roof arch is formed from three curves meeting at tangents and, whilst this is stable once vertical, it has little structural strength in its minor axis. This meant that building the trusses flat on the ground and then lifting them vertically would require extensive temporary works, which with 13 to lift would have substantially increased the build costs. Building the trusses vertically on the ground was ruled out due to the height of any temporary frames which would have been required for temporary stability during assembly.

The solution was to utilise the permanent design for the temporary works. Simple stubs were designed to transfer the load from truss to truss with chord ties, and then match all these stubs at each truss so truss components could be connected directly to the previous truss; this allowed a full truss to be built in the air. The challenge was then how to erect the first truss! As this was at a gable the slender gable posts, which were themselves trussed, could be propped first and then roof truss segments landed on top and joined together to form one complete arched truss.

All the steel structural elements were very precisely fabricated to tight tolerances before delivery to site, which enabled a rapid waste-free assembly and a comparatively quiet construction process. This was important as the existing Centre and Academy buildings needed to remain open during the construction work. Erection procedures were planned in detail using 3D models.

The steel-framed structures and regular column grid arrangement for the office, café and elite sports areas are all adaptable for future changes of use.

The structural steel was efficiently engineered for fire resistance with the structural elements supporting floors required to achieve a 60 minutes’ fire rating. For exposed elements this was achieved through the use of high visual quality intumescent paint. For those which are not exposed, intumescent paint with a basic finish was used.

The project team has delivered a world-class facility that also provides extensive access for the local community.

Judges’ Comment

Two parallel vaulted forms spring from a central spine; the larger one covers a football pitch, whilst the smaller covers a sports hall. The elegant lightweight steel trusses resulted from a collaborative effort by the designers and contractor, with the construction methodology informing the roof structure and supports from which it springs.

Striking and effective steelwork.

The Memorial Spire, International Bomber Command Centre, Lincoln

The Memorial Spire

Architect
Place Architecture

Structural Engineer
s h e d

Steelwork Contractor
S H Structures Ltd

Main Contractor
Lindum Group Ltd

Client
The Lincolnshire Bomber Command Memorial Trust

The International Bomber Command Centre (IBCC) is being created to provide a world- class facility to serve as a point for recognition, remembrance and reconciliation for Bomber Command. This is an ongoing project being driven by The Lincolnshire Bomber Command Memorial Trust, in partnership with the University of Lincoln, with the aim of opening the Centre in 2017.

Lincoln has been chosen as the site for the IBBC as Lincolnshire earned the title of Bomber County – it was the home of 27 operational bases which in itself was a third of the UK’s Bomber Command bases.
At the heart of the IBBC is the Memorial Spire which sits majestically above the City of Lincoln and acts as a beacon marking the courage and bravery of those who served in World War II.

The architectural references are taken from the airframe and wings of an Avro Lancaster Bomber. The structure represents two wing fragments tapering towards the sky, separated by perforated plates similar to those used in the aircraft’s frame construction. Further references can be found in the Spire’s dimensions, standing 31.9m high this represents the same span of a Lancaster’s wing and, at 5m wide at its base, is the same width of the aircraft’s wing.

The Spire’s orientation was carefully considered and it is placed so that visitors who walk through it will be rewarded with a framed view of Lincoln Cathedral. The Cathedral Spire was very familiar to the aircrew as it was a welcoming landmark to those who returned from their many sorties during World War II.

The facts and figures relating to the role of those young men who flew from airfields around Lincolnshire and other parts of the UK are thought provoking: 364,514 sorties flown, 3,491 aircraft lost and 25,611 aircrew losing their lives, with the average being 22 years old. To recognise the sacrifice of the aircrew the Spire is surrounded by a series of Memorial Walls. The weathering steel panels are laser cut with the names of those who lost their lives.

Steel was the obvious choice for the Spire and the weathering steel plate fulfilled all the structural and aesthetic requirements of the project. The selection of weathering steel gives the Spire a cold austere feel which, whilst not requiring applied surface treatments, will be maintenance-free throughout its lifespan.

The first part of the manufacturing process was to cut the individual plates. Using the information generated by the computer model the plates were carefully nested to minimise the overall waste of material. The external profiled plates had to be curved to create the wing-like form. This was achieved by press-braking the individual plates to the desired shape using files extracted from the 3D model.
The formed plates were built up in purpose-made jigs prior to being welded together to form the complete spire sections that would go to site as two loads. Due to the significant amount of welding, a great deal of care had to be put into the developing of the weld procedure to ensure there was no distortion in the plates, particularly along their leading edges where any defects would be most noticeable on the finished spire.

With fabrication complete the two sections of the spire were shot blasted – a process that would ensure any fabrication marks were removed and allow the structure to develop an even patina as the weathering steel gradually turned its familiar rusty colour.

On 2 October 2015 in front of an audience of 2,600 guests, including 312 Bomber Command veterans thought to be the largest gathering since 1945, the IBBC Memorial Spire was officially unveiled.

We all go about our working lives and spend time with our families and friends and it is easy to forget that the freedom we have today is thanks to those who gave so much during World War II. To be reminded about the sacrifices made by so many is a humbling experience. The Spire is a fitting memorial and, when further funding is in place, the construction of the Chadwick Centre will begin, which will house the Bomber Command archive and tell its story to future generations.

Judges’ Comment

This excellent project is a fitting testament to the memory of the World War II bomber crews that flew from Lincolnshire and other parts of the UK. The architectural arrangement of the various elements has been carefully considered, taking cues from the local context. The choice of weathering steel is most successful.

The detail design and particularly the execution of the monument are outstanding.

Heathrow Terminal 2B

Heathrow Terminal 2B 1

Architect
Grimshaw

Structural Engineer
Mott MacDonald Ltd

Steelwork Contractor
Severfield

Main Contractor
Balfour Beatty Plc

Client
Heathrow Airport Ltd

T2B is a satellite pier for the new Heathrow Terminal 2. The structure is rectilinear in form and accommodates 16 stands. A 520m long steel-framed superstructure sits above a two level basement. By elevating arriving passengers over departing, the building offers a sense of space and inverts the familiar ‘undercroft’ experience of the arrivals journey.

The use of structural steel was essential to delivering the satellite pier to the client’s programme. Using steel plunge columns allowed excavation of the basement by top- down construction while the pier’s structural frame was erected above.

Among the first elements fabricated and installed onsite were the 163 plunge columns, assembled from the heaviest UC section and two 40mm thick steel plates, welded together to create a thick-walled box. The efficiency of this section and the novel ‘top hat’ connection – which transfers load from the concrete apron slab into the columns – allows unrestrained column lengths of up to 15m despite loading of 20MN.

Cold-formed steel sections were assembled into lightweight wall and ceiling panels to form the supporting structure for the arrivals corridor cladding.

The design team collaborated across disciplines using a 3D model environment, with the construction team extending this to produce 4D construction phasing and test access routes for mechanical plant modules. The 3D environment allowed virtual testing of exposed steel connection details ahead of fabrication.

To create a large, open space for the central hub, long-span cellular beams were used spanning onto the Vierendeel truss of the arrivals level bridge. This reduced the number of columns needed within the open area to just two, discretely positioned beneath the footbridge.

Architects and engineers worked together to develop a range of connection details and structural concepts that weave the steel frame into the architectural fabric. Suspending the internal glazed screens from roof level keeps the size and visual impact of supporting mullions to a minimum.

Prefabricating elements offsite ensured construction efficiency, minimised wasteful site-based construction activity and eliminated impacts on airport operations. The use of prefabrication, together with time-based 4D BIM, allowed virtual testing of safety issues, which could then be designed out.

By taking a fire engineering approach and limiting the fire load within the passenger concourses, it was possible to omit fire protection to the exposed steelwork.

The design embodies collaboration between architecture, engineering and construction to create an elegant expression of its lean design principles.

T2B is the first UK airport facility to achieve a BREEAM rating of ‘Very Good’.

Judges’ comment

A large and complex project, with severe demands (25% less cost and 10% less time than previously achieved) required the whole team to work exceptionally well and closely in order to satisfy a demanding and knowledgeable client. The varying degrees of complexity of the steelwork, and its architectural exposure, were very well planned, detailed and executed.

A success for steelwork in a challenging flagship project.