Design Awards: 2013: Commendation

The Saints Stadium Bridge, St Helens

saints stadium bridge
© Moxon Architects

Architect

Moxon Architects Ltd

Structural Engineer

Flint & Neill Ltd

Main Contractor

Galliford Try

Client

St Helens Council

The new Saints Stadium Bridge in St Helens is an example of excellent cooperation between the client, contractor, design team and specialist suppliers in order to deliver a high quality, attractive and extremely cost effective solution. The project was compressed into a very tight programme and illustrates what can be achieved in terms of best practice in the construction industry on a small scale project.

When the developer sought planning permission for a proposed stadium the proposals included minimal on-site provision for car parking. St Helens Council accepted this principle but made it a primary condition of approval that a footbridge would be provided to link the site to the town centre. This would allow pedestrians to safely negotiate the A58 dual carriageway, which runs along the north boundary of the site.

The client’s budget was comparatively low, presenting a number of challenges. A contract to design and construct the bridge was awarded to Galliford Try together with Flint & Neill and Moxon Architects, under a competitive tendering process in which the team’s ability to work in a partnering framework to meet the extremely tight programme requirements played a significant part.

A single span was preferred for aesthetics and to avoid a central support in the middle reserve of the A58. Steel was selected for the superstructure in order to meet the fast track programme and to maximise offsite prefabrication, thereby minimising work on site and improving quality control.

With an overall length of 60m the bridge features a dramatic parabolic arch from which the deck is suspended via flat plate hangers. A key feature of the bridge is that users see two arches on the approaches, whereas the arches are formed from a single continuous element passing under the deck at either abutment.

Extensive three dimensional modelling was used during the planning stage to develop realistic images of the finished structure and, at the detailing and fabrication stages, to develop the complex geometry of the bridge.

Able to accommodate very high pedestrian flows exiting the stadium, the 4m wide deck is suspended from the arch by unique flat plate hangers, chosen in place of proprietary bar or cable systems. Hangers were made from 50mm thick plate and a novel arrangement was devised that incorporated compact recessed spherical bearings at the connections to the arch and deck at each end.

These bearings allowed the hangers to be rapidly installed on site, thereby greatly reducing the amount of site welding that would have otherwise been required and helping to meet the tight programme.

The bridge is one of the first structures in the UK to be designed entirely to the Eurocodes. The application of the Eurocodes allowed the design of the arch in particular to be optimised by using sophisticated analytical techniques to produce a very economic superstructure design.

The deck itself is a closed box, primarily for efficiency but also to provide a smooth soffit for improved durability and to achieve the architectural aspirations. Fabricated from weathering steel, the deck is unpainted on the inside.

After completion of the foundations the arch was delivered to site as two springing sections and two sub-sections for each arch. The springing detail was developed to maintain the appearance of the arch resting lightly on a stool.

Temporary bolted connections at the base of the arch, subsequently hidden within the arch section, were devised by the team to permit the arches to be assembled safely without the need for substantial temporary works.

Construction of the bridge was completed in December 2011.

Judges’ Comment

This elegant bridge is a key part of the development of the stadium, providing most of the pedestrian access. The plan form reflects the shape of a rugby ball, producing tough fabrication challenges as the elements are non-planar. The construction work needed to avoid disruption to traffic on the major road.

The result is a fine steel landmark structure.

Marlowe Theatre, Canterbury

marlow theatre
Photograph: Helene Binet

Architect

Keith Williams Architects

Structural Engineer

Buro Happold

Steelwork Contractor

DGT Structures Ltd

Main Contractor

ISG Jackson

Client

Canterbury City Council

Canterbury’s Marlowe Theatre is a vibrant public building that is fully accessible to patrons, staff and visiting artists alike. The theatre complex is well positioned to attract the best touring productions and shows as it offers two venues within one building: the Marlowe Theatre and auditorium, and the Marlowe Studio, a new, flexible, multi-purpose performance space designed to seat 150 people.

This complex steel structure brings drama to the site, with cantilevering and hung structures defining different spaces and creating exciting open public areas. The flexibility of steel construction allowed the design team to develop a challenging structure with frequently varying floor levels in a cost effective way.

The client was keen to ensure that a sense of flow and space was maintained in the foyer, improving pre-performance and interval movement and comfort levels, and leading to an increased use of the theatre’s facilities.

An innovative steel solution was developed to achieve this and create a highly flexible and spacious front-of-house area. The first and second floor foyer spaces were hung from trusses in the roof. The hung foyer steelwork forms the backspan of the auditorium balcony cantilevers.

To further ensure flexibility and drama within the foyer a cantilevering set of stairs was designed with minimal vertical support. This trussed structure was designed to incorporate the handrail and lighting detail into the top chord, maximising the structural depth and ensuring an adequate dynamic response.

The new auditorium space creates a closer relationship between the audience and performers with no seat further than 25m from the stage. Services are integrated throughout the steel structure, with low velocity air distributed into the auditorium throughout the structure at floor level.

The site identified for Marlowe Theatre was originally the location of a 1930s Odeon Cinema and had undergone several transformations, including the addition of a fly tower during the conversion to a repertory theatre in the mid 1980s. The decision was made to retain the fly tower steelwork as an integral part of the new theatre complex, and help to reduce the development’s environmental impact through the re-cladding and reuse of existing steelwork. A new steel framed pinnacle was designed to cap the fly tower and give the building a new iconic form, with a new tensioned mesh ‘jacket’.

A major benefit of the rebuild has been the creation of the 150 seat Marlowe Studio. The smaller of the two venues, it cantilevers out above the café towards the river; adding further opportunities for performances at the site. The floor of this space has been designed to carry a collapsible seating system creating a highly adaptable space for future flexibility.

The site’s proximity to Canterbury’s historic city centre, a highly regulated conservation area, was a major challenge, with the site categorised as a Scheduled Ancient Monument.

During construction the remains of a Roman villa were discovered while excavating near the existing fly tower. The team developed a lighter steel framed core, which allowed for the implementation of a shallower foundation and minimised disruption to the archaeological remains and ensured the construction programme was unaffected.

Judges’ Comment

This project faced challenges from archaeology, flooding and incorporating the original fly tower, all in the demanding town-planning environment of historic Canterbury.

The complex layout of the 1,200-seat theatre and back-of-house demanded very careful design and detailing of the crucial steelwork, which has proved most successful.

Brent Civic Centre, Wembley

brent civic centre

Architect

Hopkins Architects

Structural Engineer

URS

Steelwork Contractor

Bourne Construction Engineering Ltd

Main Contractor

Skanska

Client

Brent Council

Brent Civic Centre is the UK’s greenest public office building, and the fourth in the world, after receiving a BREEAM ‘Outstanding’ rating of 92.55% from the Building Research Establishment. It incorporates natural ventilation, sustainable materials, a green transport plan, rainwater harvesting and a combined cooling, heating and power plant which uses waste vegetable oil.

Brent Civic Centre will accommodate 2,300 staff, who currently work from 14 different buildings spread across the borough. The building will also be open to the public, through the provision of a library, event and ceremony facilities, and a covered winter garden.

The complex project included the construction of two separate nine-storey steel structures; an L-shaped office block housing staff, and the main drum-shaped civic building. Both are connected by a steel framed glass fronted atrium occupying the full height of the structure.

Brent Civic Centre is a combination of architectural finesse and robust structural systems. Diverse materials were used on the frame’s construction, but only structural steelwork could provide the intended aesthetics with a combination of eloquently engineered details. Each area of the building has a variety of different architectural features encompassing steelwork.

The architectural intent was clear from the onset – the finishes had to be high specification and the connections had to be carefully detailed; after all, parts of the building will be used for civil ceremonies and events. The 900t of structural steel used in the construction are prominent in the building’s overall structural and architectural scheme, meaning the highest quality architecture was expressed.

The steel members arrived in 15m long sections and were lifted using tower cranes, which were designed specifically for the weight and reach required to install these members. Erection of the lantern was possible by lowering dismantled sections of a ‘spider mobile’ (elevating working platform) onto level three, reassembling it and then lifting each steel section in a strict sequence.

Accurate scheduling of steel components during the design process not only reduced costs, but also waste, time, energy and materials, which helped reduce the project’s environmental impact. The transportation of the steelwork was also a key consideration too, minimised through strategic deliveries and scheduling of steel items.

The project presented a number of engineering challenges, which included the different tolerances posed by the structural steelwork and concrete elements of the building. This was resolved through the erection of the external columns and cross-bracing steelwork prior to the casting of the edge beams, which in turn were supported by falsework until the floors had been post-tensioned and the edge beams cast.

BIM was used during this project to track certain components of the programme including scheduling, sequencing, deliveries and erection progress. The 3D model was discussed weekly, aiding coordination of interface details between steel, concrete, timber and cladding.

Erection of the steel frame commenced in March 2012 and was completed seven months later in October.

Judges’ Comment

New civic facilities comprise an office building and a voluminous steel framed entrance atrium. This space houses a large cylindrical form containing the council chamber and function rooms.

The steelwork throughout the atrium, supporting the ETFE roof, glazed walls, exposed glass lifts and connecting bridges, is very light, elegant and immaculately detailed.

Steelwork is key to this impressive civic space.