A new state of the art transport hub in Newport, designed by Atkins with architectural support from Grimshaw, is now complete as part of a city-wide regeneration masterplan. Atkins’ technical director Mike Otlet describes the challenges of working on such an innovative and ambitious project.
Atkins’ multidisciplinary engineering design team was appointed back in 2006 to develop the design for two terminal buildings, accommodation blocks and a connecting foot bridge, as well as the external works for a landmark redevelopment of Newport station. As the principal consultant on the project, Atkins was engaged in providing civil and structural engineering, building services, landscape architecture, rail, telecoms and pedestrian flow expertise. The station architecture was sub-contracted to Grimshaw.
The project’s ambitious brief required that a functional and welcoming station be developed, with a modern design to bring the city of Newport into the 21st century. As the gateway to the city – and indeed to Wales – the resulting station needed to combine traditional station facilities with fresh and contemporary design.
Now open to the public, the new 2,100 square metre station is nearly twice the size of the previous building and already gaining iconic status locally. The modern design also introduces some key operational energy saving elements such as the use of natural ventilation on the concourse and low power lighting in many areas.
Innovative design
This is a station where user needs have been integral to the design thinking. The overall concept features two aluminium-clad spiral steel structures linked by a connecting bridge. The spiral form of the main structures influences and eases passenger traffic flow, and creates a futuristic organic architectural form. Passenger movement is mirrored by the internal spaces which instinctively guide pedestrians from ground level up to the connecting bridge and back down onto the platforms.
The design is unique and while it is highly functional the unusual architecture and geometry created some interesting technical challenges. Atkins’ technical team worked hand in hand with Grimshaw’s architects combining creativity with practicality, and this was particularly evident in dealing with the egg-shaped oculi terminal buildings.
The structures’ egg-shaped geometry meant that particularly careful attention had to be paid to tolerances and adjustments in order to help the speed of fabrication and construction on site. Fabricated rib sections, tapering in response to the forces, were also created to follow the external profile of the enclosure which gave us a highly practical solution.
The connecting bridge is another bespoke solution to an engineering problem. Limited space for supporting columns on the island platforms necessitated the construction of a lift enclosure that could also support the three bridge spans. To achieve this, a steel plate torsion ring beam was fabricated to sit above the reinforced concrete drum, with tapering cantilever arms to support the load-bearing truss ends of each of the bridge spans. The bridge structures must safely support high crowd loads and are as a result stiff assemblies. A compact lattice truss was therefore concealed below the level of the handrails on each side of the walkways, which curve outwards to allow passengers to walk around the island lift uninterrupted.
Minimising disruption
The bridge section was lifted into position during track possessions and installed in four sections, all of which were pre-assembled prior to being lifted, reducing the extent of work subsequently required over the tracks. To account for the time-critical nature of the 56-hour possession period, Atkins was required to model all possible sequences of combinations for the installation of the bridge elements - including a full 3D analysis model of the bridge structure - to give the contractor maximum flexibility. Hold points were built into to the schedule and methods for locking off the ring beam were created to allow trains to safely pass under a partially-erected structure should the lift have to be aborted partway through.
State of the art materials
The cutting-edge design for the new station makes use of the innovative featherweight material ETFE (Ethylene Tetrafluoroethylene). Thirty-one air-inflated cushions, created using two layers of film measuring 250 microns - around two or three strands of hair - in thickness, make up the station’s roof to form the distinctive bubble-wrap effect made famous by the Eden Project and the Beijing Olympics’ ‘Water Cube’.
Originally designed for the space industry, ETFE is a hundred times lighter than glass, making it resilient enough to support 400 times its own weight. It requires just a fraction of the steel support of a normal glass structure, and also costs between 24% and 70% less to install.
As well allowing us to create a low mass structure, the material is recyclable, does not degrade under ultraviolet light or atmospheric pollution, and its unique non-stick, self-cleaning design means that dirt is easily removed by rainwater. As minimising the building’s energy demands and carbon emissions was a key consideration of the project, the use of ETFE provided a neat low carbon solution.
In addition to the low carbon benefits the material also transmits more light than glass and allowed us to create a uniquely bright and airy space. This brightness is accentuated by the oculus at the peak of each terminal, which allows further light into the building and doubles as a compression ring to secure the structure.
In line with Network Rail’s aspirations of creating a striking civic building for Newport, this high profile project – the greenest and biggest station work in South Wales – demonstrates a successful fusion of innovation and iconic design. The result is a station that will become an outstanding feature for the people of Newport, both for its design quality and its ease of use for the passenger.
Source : ATKIN News
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