Design Awards: 2002

The Gateshead Millennium Bridge, Gateshead

The Gateshead Millenium Bridge, Gateshead

Architect

Wilkinson Eyre Architects

Structural Engineer

Gifford and Partners

Steelwork Contractor

Watson Steel Ltd

Main Contractor

Harbour & General

Client

Gateshead Council

The Wilkinson Eyre Architects and Gifford design is the winning entry to a 1997 competition for a major new crossing over the River Tyne. The £22m project, promoted by Gateshead Council and part-funded by the National Lottery, links the newly developed Newcastle Quayside with the ambitious plans for redevelopment of East Gateshead, in particular the new visual Arts Centre at the Baltic Flour Mills and the Northern Regional Music Centre.

The brief was dominated by the requirement to retain a 30m-wide clear channel for shipping whilst maintaining a low-level crossing for pedestrians and cyclists, as well as addressing the importance of context in this place characterised by its bridges. The opening motion of the design is both its generator and its highlight. Bridges that open offer a spectacle, yet are rarely spectacular. This bridge in contrast has visual daring and elegance in its closed position, giving way to theatre and power in operation.

The idea is simple; a pair of arches, one forming the deck, the other supporting it, pivot around their common springing point to allow shipping to pass beneath. The motion is efficient and rational, yet dramatic beyond the capabilities of previously explored opening mechanisms. Two synchronised batteries of three hydraulic rams located in each end support provide motive power to the base of the arch, 4.5m below the bearing centreline. The whole bridge tilts, and as it does the entire composition undergoes a metamorphosis into a ‘grand arch’ of great width and grace, in an operation which evokes the action of a closed eye slowly opening.

The scheme is wholly informed by the need for a legible integration with the Tyne’s existing bridges and with its particular context. The design is a mix of the robust combined with an overall lightness to contrast the visual mass of the Baltic Flour Mill. The soaring 45m-high arch provides instant visual reference to the Tyne Bridge beyond, but presents a slender profile against the skyline, interpreting and updating the structural and aesthetic order of its neighbour.

The lighting design by Jonathan Speirs & Associates elegantly balances function and spectacle to highlight the structural form and incorporates deck-mounted long-life LED waymarkers, below-deck ‘riblights’ and computer controlled colour-change spotlights which illuminate the main arch with a constantly varying scripted display.

The bridge spans 105m between new concrete end supports founded in the river and lying parallel to the quay sides. Access to these caissons offers exciting additions to the functions of the bridge, allowing a simple glazed hall on each to provide amenities in a highly dramatic location with incredible views of the structure and the Tyne.

The bridge between the two caissons features two parallel decks separated by level and by intermittent perforated stainless steel screening to differentiate pedestrian and cycle paths. Pedestrians are allowed clear views over the lower cycle deck, and seating and other amenities promote the bridge as a place as well as a crossing.

The parabolic arch comprises a kite-shaped cross section tapering in both plan and elevation, fabricated from internally-stiffened steel plate up to 35mm thick. The main pedestrian deck is a similarly fabricated steel box, parabolic in plan and narrowing from the quaysides towards the centre of the river. Spiral strand stay cables link arch and deck sections, with carefully detailed anchorage lugs on the arch and recessed cylindrical anchorages within the deck. The lower cycle deck features a lightweight open-grille aluminium surfacing supported from the main deck on cantilevered arms.

The complex steel superstructure was fabricated at Watson Steel in Bolton and transported in sections to the AMEC works at Hadrian Road, Wallsend where arch and deck pieces were welded together and painted, lying flat, before being raised and joined. The entire super-structure was transported the six miles to its final position in Gateshead in November 2000 using the giant Asian Hercules II floating shearleg crane, and successfully lowered into position to a tolerance of ±2mm.
An NEC Target Cost Contract with Bill of Quantities was adopted, with Harbour & General/Volker Stevin appointed Main Contractor and Watson Steel and Kvaerner Markham sub-contractors for steelwork and M, E and H respectively.

Gateshead Millennium Bridge is conceived as being in the great tradition of engineering in Tyneside and represents the revitalisation of the Gateshead riverfront. The unique, challenging design has been transformed into a functional, beautiful and iconic new landmark for Gateshead and the north-east, and has proved highly popular since its public opening in September 2001.

Judges’ Comment

s:

A fundamentally simple concept which exactly matches the complex requirements of the brief has been implemented with great assurance and elegance to produce a very fine bridge for pedestrians and cyclists. It can take its place confidently alongside the great bridges crossing the Tyne built by earlier generations.

TNT FastTrack, Magna Park, Lutterworth

TNT FastTrack, Magna Park, Lutterworth

Architect

Chetwood Associates Ltd

Structural Engineer

Burks Green

Steelwork Contractor

Barrett Steel Building Ltd

Main Contractor

UKGSE

Client

Gazeley Properties Ltd

TNT UK Ltd urgently required a large distribution facility for their subsidiary TNT Retail Services to service Primark, the fashion retailer trading from 103 high street locations in the UK. TNT were convinced that fitting out an existing building would be the only option open to them. The ideal solution would be a bespoke facility, an option now available to clients through FastTrack.

FastTrack is the name of Gazeley Properties’ new concept in distribution developments – a fully operational facility in 10-12 weeks. The TNT project demanded a 412,000 sq ft facility to be operational in 12 weeks. 40 weeks is a typical build programme for a bespoke building of this size.

The project:

  • Design and build a 1600 tonne steel framed distribution facility.
  • Three and a half week erection programme, compared to a normal 15-week programme.
  • The project’s success rested on the steelwork contractor’s ability to meet this programme. Follow-on trades required carefully phased handovers – the first after just four days, to start cladding.
  • Steel – the only material capable of meeting such a demanding programme.
  • “Speed engineer” to maximise on-site production; a shift from traditional minimum weight design.
    • reconfigure the building layout, span frames to maximise the working fronts during erection.
    • rationalise the number of cold rolled items, they require the most restraint by ancillary items and slow down erection progress.
    • robust members require fewer restraints and are faster to erect.
    • minimise the number of pieces to erect.
    • reduce time working at high level to increase safety.
  • Detailed design development commenced just six weeks before the steelwork was due on site, the 3-D model progressing in tandem.
  • Supply chain ethos was essential. The programme was not achievable through traditional tendering means.
    • Gazeley partnered their supply chain.
    • an opportunity to showcase three years work on the steelwork contractor’s supply chain: steel, erection, paint, bolts, transport, cold rolled purlins and rails were all partnered.
  • Work with associates (eg the cladders, door and dock door company) pre-agreed – standard details were used to speed up design and drawing and eliminate interface problems.
  • Effective project management the key.
    • Meticulous planning of the 85 loads, delivered every two hours in erectable lots to a site team of 30 men, four cranes and 16 cherry pickers.

The results:

An extract from an on-site diary at the end of week four of the building contract read: “The steel frame is blitzkrieging its way across the field, the Barrett boys have had a fantastic week’s production – 800 tonnes of steel erected, lined and levelled since they started seven days ago. We believe that this rate of production is a European, if not World, on-site production record for a portal framed building of this type. The organisation from factory through delivery to erection is as slick as can be.”

By day 20 the entire 1600 tonne building was handed over to the main contractor, beating the programme by five days. This was achieved without compromising the most important factor on any building site, safety. Ground conditions were close to perfect, the most important factor in safe erection of steelwork.

Exactly 12 weeks to the hour from when the first foundation was dug, TNT’s vehicles were being unloaded.

This project is a case study in the unique properties of steel allied to effective supply chain management, both are key to a successful outcome of a unique challenge and a satisfied client.

Judges’ Comment

s:

A powerful team effort, which delivered a remarkably fast project, necessitated by the demands of a distribution business, but with no compromise in quality. A finely engineered solution, only possible in steel.

The Falkirk Wheel, Falkirk, Scotland

The Falkirk Wheel, Falkirk, Scotland

Architect

RMJM

Engineers

Arup Scotland
M G Bennett & Associates Ltd
Butterley Ltd
Tony Gee and Partners

Steelwork Contractor

Butterley Ltd

Main Contractor

Morrison Bachy Soletanche
Joint Venture

Client

British Waterways

By any measure the Falkirk Wheel is an unusual structure. Weighing approximately 1400t without water it is a large machine. Raising and lowering boats in a rotary motion makes it unique.

Being so unusual there was no prior experience on which to build the design. As part of a modern leisure facility it was essential that the architectural image be faithfully maintained. As a consequence it was essential that the concepts for the mechanical and structural solutions were developed alongside the architectural image.

The wheel concept developed is of two arms fixed to an axle. The end of each arm forms a ring within which two gondolas rotate. The very fact that the main structure is a continuous rotating machine means that the principal stresses within the majority of the rotating structure fully reverse each cycle of the wheel. Additionally as the gondolas are supported on four wheels within each arm ring then the rolling loads generate four load stress cycles on the gondola rail support structure every revolution. These fatigue limitations dominated the arms and axle structural design.

To accommodate these high fatigue cycles a combination of bolted and welded construction was adopted. This allowed the ring beam supporting the gondola rail to be a compact construction with the beam diaphragms bolted to the flanges and only welded at the mid third of the beam webs. This cyclic loading and relative flexibility of the ring beams meant that the connection of the beaks, an architectural feature, to the arms would have to either form an integral structure or be so contrived as to not add to the stiffness of the arm ring beams. The latter option was adopted and the beaks are effectively hung from their centres, with flexible connections at their ends capable of taking the out-of-plane wind loads.

The axles presented a particular challenge. The ideal was to fabricate as a single unit. This did not allow trial erection into the arms. To accommodate this and maintain the smooth architectural lines bolted flange joints were included approximately 1m from the arms with the flanges inside the tube of the axle. The fatigue considerations entailed these being constructed using forged rings fabricated into the tube ends with high tensile pre-loaded bolts to form a fatigue resistant joint.

The arms are constructed in sections for HSFG bolt connection on site. The joints were arranged to not only accommodate transport difficulties but to add to, rather than detract from the architectural effect. In all the joints used some 14000 bolts.

The gondolas are a constantly loaded structure. Had they been static structures there would have been no need for torsional stiffness between the ends. They are, however, rolling within a circular rail and to ensure they remain horizontal at all times they have a timing gear mechanism driven from a static gear on the aqueduct tower.

To transmit the rolling forces along the shallow open trough gondola with insignificant torsional flexure required the side beams to be of box construction.

Due to the forces generated within the wheel and resulting deflections it was essential the structure was sympathetic to the loading of the mechanical equipment and likewise the mechanical equipment was designed to be sympathetic to the structure.

This entailed not only producing finite element models for the wheel structure but also separate models for the gondola ends and the main shaft flange bolting. The models were used in particular to predict the loadings on the rolling elements of the main bearings, the alignment of the main drive gears and the fluctuating loads within the main bearing bolts.

As stated earlier there is no specific prior art on which to base the wheel design. While, in general, design for wind loading is well known, the nature of the wheel design led to possible interactions within the structure. Wind tunnel tests were therefore undertaken to confirm the dynamic response of the structure.

Only by employing these detailed techniques was it possible to produce an efficient design realising the architectural aspirations developed in the initial concepts.

The structure including the gondolas was designed to eliminate all site welding and facilitate the full works trial erection of critical elements.
The wheel was delivered to site by road in some 40 major components. The longest element was approximately 21 metres, the widest 5 metres, the highest 5 metres and the heaviest approximately 80 tonnes.

The individual elements were pre-assembled at low level into a series of major lifts.

The main erection was carried out in a five-day period using a Demag TC3300 (1000t capacity) strut jib crane.

The maximum single lift was 270 tonnes. The gondolas (complete with bogies and gearing) weighed approximately 180 tonnes and were both erected on the same day.

The main erection was completed in September 2001, and the fitting of ancillary steelwork, gates and other components were completed in time for the first turn of the wheel in early December.

Judges’ Comment

s:

Reminiscent of the engineering feats of the past, this project has produced an innovative and unusual structure. Its apparent simplicity belies the complex engineering and fabrication solutions that have been devised and used to both construct and operate safely, this eye catching, large machine. In its setting, it will be a long lasting demonstration of engineering in steel.

The Magna Project, Rotherham

The Magna Project, Rotherham

Architect

Wilkinson Eyre Architects

Structural Engineer

Connell Mott MacDonald

Steelwork Contractor

Billington Structrues Ltd

Main Contractor

Schai International Management Ltd

Client

The Magna Trust

Magna is a Millennium Commission funded building that re-uses the redundant steelworks at Templeborough, Rotherham to create a hands-on science adventure centre organised around the Aristotelian elements _ Earth, Air, Fire and Water.

The enormous main sheds at the steelworks have been stripped of extraneous ancillary buildings, the existing profiled metal skin has been repaired and
the whole has been painted black to protect and unify the exterior.

The interior of the shed is an awe-inspiring space with a scale and grandeur only hinted at by the exterior. Four new pavilions house the exhibits and provide environmentally controlled conditions. The form, location and construction of these pavilions relate to the respective elements and together with the existing artefacts, retained from the steel making processes, combine to make a new composition.
Visitors may explore these pavilions and the main shed with the horizontal walkway links and vertical circulation elements located at the refurbished Transformer house in the centre of the space.

The new elements are steel-framed structures supported from the massive stanchions that previously supported the crane gantry rails.

The Air Pavilion is clad in three layers EFTE cushion clipped to aluminium extrusions held in position with a cable net tension structure. Air inflation maintains the form and insulation value of the envelope.

The Water Pavilion is clad in stainless steel sheeting pre-curved to follow the spiral form. A pre-filled metal stressed skin provides the substrate and lateral restraint to fabricate steel ribs at 3m centres.

The Fire Pavilion is suspended across the two main aisles with a three-dimensional latice floor structure. A proprietary black composite cladding provides the enclosure.

The Earth Pavilion is supported from existing and new columns at basement level that support both the floor and roof structure. The roof is clad in pre-rusted steel sheeting supported by profiled metal decking.

Wilkinson Eyre Architects were appointed in July 1998, enabling works comprising site remediation, demolitions and strip-out packages commenced in April 1999. New construction commenced from January 2000 and was complete in March 2001.

The project opened to the public in April 2001, and has proved a popular success with over 100,000 visitors in the first six weeks.

Judges’ Comments:

The Templeborough Steel Works once reverberated to the roar and hammer of steel making. By an intelligent use of the existing fabric, combined with the use of light to create atmosphere and excitement, the interior has been transformed into Magna. This Exhibition and Education centre has a variety of steel pavilions reflecting the themes of the exhibition.

National Space Centre, Leicester

National Space Centre, Leiceste

Architect

Nicholas Grimshaw & Partners Ltd

Structural Engineer

Arup

Steelwork Contractor

S H Structures Ltd

Main Contractor

Sir Robert McAlpine Ltd

Client

The National Space Centre

The National Space Centre is the UK’s only attraction dedicated to space science and astronomy.

The design comprises three principal elements: a main podium, an annexed rocket tower and a prefabricated Challenger Learning Centre. Together, these elements form an exhibition venue of international standing and a new centre of excellence for education and research affiliated to the University of Leicester.

The podium is a double-height space (6m high) built on a lightweight 14m-grid steel frame. It is capable of accommodating a flexible arrangement of exhibition display systems as well as the full integration of structure and service zones. It has been created as a 5,000m2 square-plan structure in the renovated shell of the disused storm-water tank.

The podium is ‘wrapped’ in a double skin, comprising an inner wall of fenestration and silver sinusoidal steel cladding with a homogenous outer screen of perforated stainless steel panels. In practical terms, this affords privacy to offices and facilitates the optimum environment for the safe display of sensitive artefacts.

The podium contains administrative and research facilities affiliated to the University of Leicester in addition to the public Visitor Experience, a 2.5-hour interactive exhibition. Organised in a ‘hub and spoke’ arrangement, the Visitor Experience is designed to facilitate visitor flows for the Space Theatre, a state-of-the-art planetarium. This huge geodesic dome (20.5m) perforates the roof slab at the centre of the exhibition space, acting as a foil to the soaring vertical form of the Rocket Tower.

The tower has been designed as a showcase for high-profile international exhibits, most notably the ‘Blue Streak’ F16 and Thor Abel rockets. Its volume has been defined by the dimensions of these exhibits, with its highest point (42m) proportionate to that of the largest rocket installed (26m).

The volumetric requirements of the tower are expressed in its structural skeleton. The primary curving structure is composed of a series of simple steel arcs of varying radii – attached end-to-end and rotated one to the other, braced by a vertical concrete stair core. The geometric configuration of the tower structure, with its combinations of curves and in-line twists, represented an interesting challenge for the structural steel subcontractor, S H Structures. They commenced their detailed design work using a 3-D model (developed by the architects in collaboration with the engineers) as a starting point. With the use of current CAD technology, this could be relatively easily manipulated, allowing the team to work efficiently on the basic skeletal structure, despite its obvious geometric complexity.

The principal benefit of such a considered design is that it can be precisely translated to the workshop floor, in terms of simplicity of both explanation and assembly.

Horizontal radiused CHSs support an EFTE skin at 3000mm vertical intervals, approaching the maximum achievable span of the latter material.

EFTE foil is a modified co-polymer that poses no threat to the ozone layer. Weighing less than 1% of the dead weight of equivalent glass but with greater insulation properties than even double-glazing, its sustainable benefit is that it greatly reduces the energy requirements to heat the space that it covers.

The resulting envelope is an exemplar of efficiency – the enclosure of a complex 3-Dimensional space with minimal secondary support mechanisms and troublesome joints and junctions.

Judges’ Comment

s:

A slightly incongruous match between the rocket housing and the general exhibition space does not ultimately detract from the sense of wonderment, excitement and pure pleasure that this design gives to its many visitors.

Tattersalls Grandstand, Nebury Racecourse

Tattersalls Grandstand, Nebury Racecourse

Architects

Foster and Partners

Structural Engineer

Whitby Bird & Partners

Steelwork Contractor

Watson Steel Ltd

Constructor Manager

Heery International Ltd

Client

Newbury Racecourse plc

The new Tattersall Stand at Newbury Racecourse in Berkshire provides upgraded betting, viewing and catering facilities whilst also offering a new venue for exhibitions and conferences during non-race days.

The structural form was driven by the architect’s intent for a clear, bold, expressive X-frame. Primarily this differs from conventional stadium design in that the roof was not designed to cantilever forward but rather to be propped by the primary structure at its tip. The geometry of the X-frame was developed to provide efficiency within the structure whilst satisfying the client’s brief for clear floor plates. By ensuring that the horizontal, vertical and diagonal elements of the frame connected at discrete node points, forces were resolved into axial loads thus minimising bending stresses.

The structure consists of six X-frames spanning 36m on a 12m grid with service cores attached to the back. Steppings, to the front, rise to a bar level at the central node point of the X, above which is a restaurant level with projecting balconies.

The client required that the old stand be demolished and the new stand be in place between the dates of the annual November Hennessy Gold Cup race meetings. With under a year to construct the stadium the design and fabrication maximised off site fabrication in order to deliver a ‘kit of parts’ that could be readily assembled on site.

Structural stability is inherent in the plane of the X-frames, whilst bracing within the cores provides stability to imposed lateral loads in the orthogonal direction. Within the mechanism of the X-frame, vertical ties resolved the structure from out of balance loading thus preventing the central node point acting as a fulcrum about which the upper structure could pivot. A horizontal tie between the feet of the X-frame ensured that the structure resolved itself into a discrete element whereby only vertical and applied lateral wind loads are transmitted to the piled foundations.

An assessment of the sensitivity of the steel frame to dynamic loading was carried out using a finite element model. Due to the angle of rake, the primary X-frame elements do not behave like simple columns but have a complex beam-column characteristic in which the structure has a tendency to combine vertical deformation with sway. The analysis studied the global type mode shapes and the largest conceivable energy input of a capacity crowd jumping in time.

The relatively short spans and large number of openings in the service cores favoured a concrete filled metal decking that could be simply trimmed to suit the irregular floor plate. The bar and restaurant clear floor plates were constructed using pre-cast concrete planks with a structural topping spanning 6m.

To meet the architect’s specification for a high finish to the concrete steppings the units were fabricated off site and sequenced in delivery to be lifted straight into position so as to minimise handling and the possibility of damage.

Judges’ Comment

s:

This grandstand has a transparently open feel that displays the primary “X-frame” structural form to its best advantage. It is clearly a winner with the client, fulfilling the project brief by providing excellent usable space and sight lines throughout. The designers are to be congratulated on a splendid team effort.

Premier Place, Devonshire Square, London EC2

Premier Place, Devonshire Square, London EC2

Architect

Bennetts Associates Architects

Structural Engineer

Waterman Partnership

Steelwork Contractor

Wescol Glosford plc

Main Contractor

Carillion

Client

AXA Sun Life Properties Ltd

Following a limited competition in 1996, Bennetts Associates were appointed by BT Properties to design an office building on the site of its redundant Houndsditch Telephone Exchange.

Having gained planning permission, the site was bought by AXA Sun Life who commissioned Bennetts Associates to develop the project to completion, which was achieved within its £45 million budget in October 2001. The building has been pre-let to the Royal Bank of Scotland.

In sympathy with the industrial Victorian warehouses nearby, 2 1/2 Devonshire Square expresses its structure within a rugged, load-bearing steel and glass façade. The design orientates the building away from Houndsditch and places the main entrance on the corner of Devonshire Square.

Incorporating the client’s floor space requirements, respecting the proximity of a conservation area and rights of light limitations, the building steps back from Devonshire Square on the sixth floor, rising up to nine storeys along the Houndsditch elevation.

Lifts and staircases in the glazed service cores animate the exterior of the building and provide a series of minor landmarks at critical points in the townscape. These vertical elements, accentuated by towers of meeting rooms framed by shear walls clad in granite, act as “bookends” for the principal steel elevations. Solar shading adds to the textural qualities of the southern façade.

The decision to expose the structural steel frame of the Devonshire Square building created a number of inherent technical challenges:

  • Developing an appropriate language of steelwork detailing and finishes
  • Addressing potential cold bridging problems
  • Vapour and condensation control
  • Fire engineering issues
  • Understanding the movements, deflections and tolerances of exposed steelwork
  • Corrosion protection issues

Standard rolled sections are manufactured as general purpose members with a relatively wide dimensional tolerance for length, depth, straightness and surface quality. While, in normal use, this is not a problem, when the steelwork is exposed on the façade, these tolerances may not achieve an appropriate visual standard commensurate with the cladding of a city office building. The façade steelwork was therefore ordered direct from the manufacturer with a more precise dimensional tolerance, and to the highest surface quality to minimise laminations, rolling marks, surface pitting and handling damage.

Judges’ Comment

s:

The special feature of this steel framed office building is its façade. Exposed steel has been used to provide both its structural form and architectural expression. Clearly articulated detailing and careful attention to tolerances has produced a building with a fine presence.

Whatman’s Field Downstream Bridge, Maidstone

Whatman's Field Downstream Bridge, Maidstone

Architect

Studio Bednarski

Structural Engineer

Flint and Neill Partnership

Steelwork Contractor

Fairfield-Mabey Ltd

Main Contractor

Lewin, Fryer and Partners

Client

Maidstone Borough Council

In May 1998 a team of Architects and Engineers were appointed to assist in the concept and design for a Millennium Project at Maidstone River Park.

The concept was to open up Whatman’s Field, a new public park, with the construction of two new foot/cycle bridges spanning the River Medway. By allowing easy access to Whatman’s Field the public are able to take advantage of new nature trails and safe landscaped areas.

The upstream bridge, a cranked concrete stress ribbon, is complemented by a downstream steel bridge inspired more by ‘landscape’ art than bridge engineering aesthetics. Due to unconventional design this bright blue 75m long bridge has a very slender appearance.

The steel box beam bridge is carried by two delicate V shaped piers. The aim was to reduce the visually perceived elevational depth of the box section. The upper, deeper, part of the box section has been set back and ‘camouflaged’ by wire mesh balustrade panels and stainless steel grills along the walking deck of the bridge. A striking blue colour was used for the visible side strip and the bottom of the box section, while the part that is set back was painted grey to make it almost invisible. At night, thanks to the lights which are set on the vertical walls of the set back box, light is shed upwards onto the wire mesh leaving the coloured narrow facia dark, only the glistening wire mesh is visible.

Circular cut outs in the bottom of the box section serve two functions. Firstly, they facilitate inspection access to the inside of the steel box sections. Secondly, they also lighten the overall appearance of the bridge and provide visual relief for the long horizontal underside of the bridge.

The bridge was fabricated in three spans. The centre span is approximately 31m long. The steel box sections were pre-cambered during fabrication. The use of the most advanced 3-D CADCAM techniques enabled the complex geometry to be easily dealt with and provided a good degree of accuracy. The holes in the flanges were profiled using highly automated fabrication machines.

The erection scheme of the bridge was restricted by the river. The Medway is a tidal river and is also navigable, a lock near the bridge allows boats to pass through at restricted times depending on the tide. Erection was only permitted during river possessions, which usually only lasted for four hours.

Two heavy duty trestles were temporarily constructed on each bank to assist in the erection of the bridge. Apart from the bolted edge boxes and parapets, all site splices were fully site welded, with welds then ground flush on all visible surfaces. Welding and subsequent painting of welded areas was carried out in a controlled environment using shelters as required.

At either end of the bridge the steel box sections bear onto concrete abutments which are supported by six piles. Embankments have been built up locally at either end of the bridge to achieve access.

All the parties involved on the project worked together to achieve a successful project outcome. The bridge allows access to rejuvenated areas and gives the local area a unique yet practicable Millennium project that can be admired for many more years to come.

Judges’ Comment

s:

The innovative cross-section with the façade and balustrade supported from the protruding underside of the main box girder, successfully leads to the objective, and the impression of a remarkably shallow structure. Careful detailing and good fabrication contribute to the high quality of this bridge – and it is hoped that the maintenance will be sustained to a corresponding standard.

MPV, Church Walk, Leeds

MPV, Church Walk, Leeds

Architect

Union North

Structural Engineer

Buro Happold

Seelwork Contractor

Merseyside Ship Repairers Ltd

Main Contractor

Simons Construction Ltd

Client

Townhouse Life Ltd

Union North was briefed to develop a set of four railway arches as a bar/club/pavement café, replacing existing retail and light industrial units. Several issues were key to the direction of the design development:

  • Railtrack were to carry out inspection and maintenance of the arches on a two yearly cycle.
  • There was a substantial area of private open space in front of the viaduct available for use as a pavement café suggesting a very outward oriented spatial arrangement and the need for measures to extend the outdoor drinking season.
  • Requirements for emergency escapes and the fact that the arches are blocked to the rear necessitated an open fronted arrangement for rapid evacuation.
  • The project is a significant distance from the main drag of Assembly Street and it therefore had to present itself as a destination in its own right with a distinctive commercial offer and visual identity to match.

The above constraints could not help but drive the design in the direction of four identical mass-produced units each in turn assembled from repeating prefabricated segments. From this starting point key design elements fall into place inevitably: rounded profiles blur floor, wall and roof into a unified all-enveloping skin; the effective legal limit on the upper floor area generates the characteristic section profile of the units fitting the surrounding arch closely at low level, tapering in above with the reduction in floor area; the front flip-up doors double as canopy and security shutter; airlock links connect the pods together through existing jack arches and the narrow alley to the rear of the viaduct becomes a connecting service void.

An industrial aesthetic suggests industrial building techniques and the pods were factory prefabricated in two metre segments, that dimension being set by the available size of mild steel plate and the maximum volume of motorway loads.

Each segment was fully welded and painted in Liverpool before trucking to site for rapid assembly by industrial forklift, necessitated by Railtrack’s restrictions regarding the use of cranes near their track installations. Completed shells were then coated internally with sprayed insulating foam.

Internally the tight fit integrated design philosophy is continued, organically shaped tubes of space snugly interlock with one another, servicing and structure disappear into the intersitial spaces between their wraparound plywood skins. Visible fittings were eliminated or reduced to simple openings in the plywood lining: ventilation grilles are perforations in an otherwise continuous skin; lighting is by concealed fluorescents in coloured voids sunk into the structural depth of the pod and washbasins reduce the slots concealing stainless steel troughs. The door counterweight and opening mechanism are concealed in a void inside the glassfibre nose. Under licensing conditions a protected route was required from upper floor areas direct to the exterior. This was articulated as a sculpted tube sweeping down through the ceiling and out through the glazed external screen terminating in clam-shell exit doors. Access doors to the stairs fold back into flush recesses on alarmed magnetic catches.

Judges’ Comment

s:

There are thousands of railway arches in the UK, and they are put to many uses. This innovative concept, of a steel shell providing surprisingly good space which is secure, whilst affording easy access to the arch for inspection and maintenance, can have wide application.