Design Awards: 2007: Commendation

Royal Air Force Museum, Cosford

Royal Air Force Museum, Cosford

Architect

Feilden Clegg Bradley Architects

Structural Engineer

Michael Barclay Partnership LLC

Steelwork Contractor

S H Structures Ltd

Main Contractor

Galliford Try Construction

Client

Royal Airforce Museum

The brief called for a masterplan for the site as a whole that would include a modern museum building. The new building was to preserve the most precious aircraft and form the background to a display that would place the Cold War into the context of the times and be more accessible to the public. The museum was to include an auditorium, two classrooms and, later, a shop.

There had to be a balance between housing all the endangered aircraft under a simple cover giving only weather protection and, at the other extreme, protecting a small number within a fully controlled environment. The choice was for an insulated enclosure that gave the 7300m2of exhibition space needed to house and reasonably protect all the military aircraft and a small number of civilian aeroplanes, together with the necessary ancillary accommodation.

The building’s form is intended to represent a fractured space in response to this concept. A simple rectangle is slipped sideways along a diagonal “fault” line giving two opposed right angle triangles. The diagonal or hypotenuse is raised as a high level spine with opposing roofs sloping down to the longer external sides of the triangles. The spine is broken in the middle to provide a connection between the display areas on the two sides, which step up from low to high and reflect the sloping natural ground.

The lecture theatre, classrooms and ancillary spaces are accommodated below the higher floor. The steel superstructure consists of a braced frame spine 25m high by 135m long, broken in the middle by a 75m “bridge”. The spine supports a series of steel truss rafters 8.4m apart with slopes that vary progressively from 25o at the gables to the vertical at the line where the roof meets the spine. Apart from its visual impact, the warped shape benefits the structural performance. The enhanced stiffness resulting from the interaction of the rafters through linking pieces allows a shallower structural depth and a significant saving in material.

The spine walls were designed to be self- supporting stable structures with the cladding in place. Having erected these walls the contractor elected to erect the rafters in a manner different from that which had been assumed. The sloping elbow pieces along the sides were erected first, the pinned bearing being temporarily fixed. Then the rafters were installed working in from the gable ends. The rafters, divided into up to three pieces, were lifted and supported in place by three mobile cranes, while erectors in cherry pickers completed the bolted flange plate connections. All the components had been trial assembled in the works, erection was fast and accurate.

Judges’ Comment

s:

This striking building celebrates theend of ‘the cold war’, and its diagonally-split rectangular form reflects the schism between the super-powers in the second half of the 20th Century.

The large space, some 25 metres high, has a hyperbolic paraboloid roof on a braced steel frame. V-bombers are suspended by steel cables from the roof, whilst other aircraft are parked below and film scenes heighten theeffectiveness of thedisplay. The mood is hard and uncompromising, with unpainted steel trussed rafters beneath the sweeping roof cladding, providing an effective and economic envelope.

The building presents a stunning spectacle on this windswept airfield, and provides an appropriate setting for an evocative experience.

Bishop’s Bridge Road Bridge, London

Bishop's Bridge Road Bridge, London

Structural Engineer

Cass Hayward LLP

Steelwork Contractor

Cleveland Bridge UK Ltd

Main Contractor

Hochtief UK Construction Ltd

Client

City of Westminster

The Paddington Bridge Project is part of a wider regeneration of the Paddington area. It originated from the introduction of the Heathrow Express Railway to Paddington Station, resulting in a parliamentary undertaking to improve the vehicular access to the station.

The main elements of the project are:

  • Widening of Bishop’s Bridge Road to 5/6 lanes between Eastbourne Terrace and Harrow Road. This entailed the demolition and reconstruction of the existing bridges over 14 Network Rail operated lines, the surface level Hammersmith and City Line, a former goods yard and the Grand Union Canal.
  • Provision of a revised taxi access into Departures Road.
  • Improvements to the junction of Westbourne Terrace and Bishop’s Bridge Road.

The complexity and risk associated with the project necessitated a partnered approach to both the site works and the preliminary planning and development of the scheme. A design and build form of contract was utilised to allow the contractor’s innovations to be applied to the demolition of old and erection of new bridge structures. The contract used was the NEC option C (Target Price). This proved successful with teamwork, value engineering and responsible contractor selection resulting in the target price being beaten and savings being shared.

The project contained many risks, however the risk associated with disruption or damage to railway operations was the largest. Over the tracks from platforms 1 – 10 was an existing 1906 bowstring bridge. Over the other lines there were various structures including steel plate girder bridges supporting masonry jack arches. The challenge was therefore to develop a scheme to remove the existing bridge and other structures and to install the new bridge structures that would ensure that the risks associated with working over the railway were minimised.

A number of methodologies were considered but the lift and launch scheme presented the most advantageous solution because critical path activities that had to take place over the railway, and hence the dependence on possessions, were minimised. The fabrication of the railway bridge above the canal bridge meant that the need to carry out welding, bolting and concreting operations over the railway was eliminated.

The scheme developed had no reliance upon abnormal possessions, thus eliminating planned disruption to scheduled train services. Furthermore, the use of easily obtainable ‘rules of the route’ possessions reduced the risk of extended delays if the progress was not as anticipated.

By far, the most complex task was the launching of the new bridge through its ‘second stage’ to platform 1. The 2500 tonne bridge was launched forward over a series of 30 nights, to programme, reaching its final position within 8mm of its designed position. The methodology developed by Cleveland Bridge UK Ltd together with the teamwork and proactive approach to risk and overcoming difficulties has resulted in the project being delivered on programme, below target price and without any disruption to the rail services.

Judges’ Comment

s:

The team were faced with enormous challenges on this constrained and busy site. The successful project to widen Bishop’s Road involved crossing a canal, London Underground and the mainline railway at Paddington.

The innovative lift-and-launch solution both to remove the old bridge and to install the new demanded planning, design and construction skills of the highest order, successfully minimising impact on the transport operations across the site.

Palestra, London

Palestra, London

Architect

SMC Alsop

Structural Engineer

Buro Happold Ltd

Steelwork Contractor

William Hare Ltd

Main Contractor

Skanska Building

Client

Blackfriars Investment and Royal London Asset Management

Palestra is a state-of-the-art, 370,000 sq ft speculative office building comprising 12 floors and two basesments, situated on the corner of Blackfriars Road and Union Street, Southwark.

Ground level and above are formed with an innovative steel frame on a 12m x 87.5m grid, comprising of double beams and concrete filled columns, that offered all up steel weight for the typical levels – including columns of 58kg/sqm. However, what is of more architectural interest is the way the building is supported by “dancing columns” (inclined columns) at both the ground and 9th floor levels. Furthermore, on the Blackfriars Road frontage, the top three floors of the building cantilever out some 9m over the street pavement.

To accommodate the changing geometry imposed by the dancing columns and the various steps in the width of the building, whilst maintaining a total floor depth – including raised floor and lighting zone – of 900mm, an innovative solution combining double beams with composite columns was developed. The solution adopted not only simplified the installation of the building services by maximising the cells through the beams, but also maximised the efficiency of the beams by using them in double bending.

Twin cellular beams span 12m and are arranged in pairs that pass either side of internal columns and as such the beams’ design takes advantage of continuity. By utilising the sagging moment capacity of the beams past the columns, this yielded beams up to 35% lighter than otherwise would have been the case. In effect each beam is acting as a single section across the width of the building with simple web plate shear, or pin splices located at the natural points of beam contraflexure. Similarly, the beams are simply connected to the columns via web plates that pass through the columns, thus ensuring that no moments are transferred into the columns.

The column construction consists of an external steel CHS filled with concrete grout with a further smaller diameter CHS placed at the centre. The design produces very high strength columns, enabling the structural engineer to provide a slim column carrying the high axial loads and an architecturally pleasing solution. The columns require no secondary fire protection even for the 120 minute fire period required.

At the west end of the building, the upper box is offset by one grid width from the lower, creating a three-storey deep 7.5m cantilever over Blackfriars Road. This impressive feature was achieved without the introduction of any visible diagonal elements in the façade or any disturbance to the internal floor space.

Judges’ Comment

s:

This headquarters building, on a strategic site south of the Thames, exemplifies modern intelligent office space of today.

Within a challenging architectural concept, the engineers have rationalised the floor structures to minimise the depths by using twin floor beams, spanning continuously over two bays, with external cantilevers. Large floor plates have been achieved on a restricted site.

This innovative solution has successfully met the unusual demands of the building form, in a fine example of steelwork for commercial offices.

Pont King Morgan, Carmarthen

Pont King Morgan, Carmarthen

Structural Engineer

Gifford

Steelwork Contractor

Rowecord Engineering Ltd

Main Contractor

Carillion Regional Civil Engineering

Client

Carmarthenshire County Council

Carmarthen County Council’s new striking footbridge over the River Towy is a landmark structure fulfilling the client’s sustainable transport needs for the local community and the region. The bridge has a clear span over the river with foundations wholly out of the river channel and back spans clear of flood levels therefore providing minimal impact on river habitats.

The form of the bridge design is a twin masted cable stayed structure supporting a fabricated steel cycle/footwaydeck which is curved in elevation and S-shaped in plan. The vertical masts are formed from shaped steel pylons which perforate the deck on its centerline. The deck widens locally at the pylon positions to provide viewing platforms for bridge users to take in the vistas of the town and river. Lateral restraint to the pylons is provided by transverse stays, between the pylon tip and deck edge beams and is supplemented by tie-down stays connecting the deck to the reinforced concrete pylon supports immediately beneath the deck.

The S-shaped deck has spans of 28m over north car park, 78m over River Towy and 44m over flood relief channel, a total of 150m suspended. It has an effective skew over the river of 25o from bank to bank and is supported on cigar shaped steel pylons 20m in height via 14 pairs of stays – two pairs of which are high tensile steel bars providing lateral stability from the tips of the pylons to tie down stays connecting the deck edge beams to the concrete piers.

The eight deck sections and pylons were fabricated and fitted out with stainless steel parapets and anti skid surfacing at the factory. These items were delivered to site overnight due to their size (up to 21m long and 5.5m wide and ranging from 7T for the pylons and 11T to 29T for the deck sections) with widest sections around mast locations loaded on special type steel frames which were positioned structures at an angle to keep components within transport limits. The sections were lifted into place using 100T, 250T, 500T and 800T cranes, the larger cranes being used for the central deck section connecting the two arms of the bridge together. Deck sections over water were pre-fitted with access scaffold at joint connections prior to installation. These sections were then aligned and temporarily bolted together using sacrificial cruciform brackets to facilitate welding of the permanent joints. Final tensioning of the stays and plumbing of the pylons followed the welding operation.

All exposed steel deck and pylon surfaces received a 25 years to major maintenance paint protective system applied in the fabrication shop. Welded site joints were 100% NDT examined on completion and the full protective paint system applied to these locations.

Judges’ Comment

s:

This slender and light-weight footbridge over the River Towy provides vital pedestrian access between the historic Quay and the railway station.

The twin-masted cable-stayed structure sits well in the landscape of the floodplain.

High quality andthoughtful detailing are the hallmarks of the bridge, which provides a landmark for the town.