The Sidings Bridge, Swansea

The Sidings Bridge

Architect

STUDIO BEDNARSKI LTD

Structural Engineer

FLINT & NEILL PARTNERSHIP

Steelwork Contractor

ROWECORD ENGINEERING LTD

Main Contractor

ALUN GRIFFITHS (CONTRACTORS) LTD

Client

CITY & COUNTY OF SWANSEA

The City & County of Swansea (CCoS) are committed to development of efficient and sustainable passenger transport systems to provide access to the City Centre from the major approach roads. Part of this strategy provides for the creation of out of town ‘park and ride’ facilities with dedicated express bus routes to the City Centre.

The eastern approach to Swansea is presently served by the Fabian Way park and ride facility which has been operational for four years. The associated express bus route had been partially constructed as advanced works and required the provision of a bridge crossing over the A483 Fabian Way. The park and ride scheme including the bridge have been financed by a combination of Transport Grant and Objective 1 funding sources.

The design brief for the proposed bridge was to provide an iconic and landmark structure carrying a single lane carriageway and a cycleway and pedestrian route across the A483. It was to be located on the site of a former railway Sidings Bridge demolished in 2003.

The design of the superstructure was procured externally through a design competition.

Substructure design was carried out by the inhouse Bridges and Structures Design team of CCoS, who also undertook the site supervision role as the Construction Management Team. Several consultants were invited to tender for the design of the superstructure on a price/quality basis, given the brief that the structure was to be of a cabled stayed form which reflects the long standing maritime history of Swansea.

The selected design proposal was submitted by Parsons Brinkerhoff Ltd in conjunction with Studio Bednarski of London.

The bridge has a 71m span at a skew angle of 65º. The design utilises separate vehicle and pedestrian/cycle decks segregated by a central longitudinal steel spine beam. The original design of the decks was based on traditional steel concrete composite construction.

The spine beam is suspended from eight cables attached to a tapered mast inclined forwards by 22º and supported by two splayed sets of twisted backstays giving the bridge a graceful yet striking appearance. The splayed/twisted backstay arrangement is intended to resemble the appearance of a sail.

The tender for construction was awarded to Alun Griffiths Ltd at a tender sum of £3.3m. With the consent of CCoS, Flint & Neill Partnership was employed by main contractor Alun Griffiths Ltd to prepare a value engineered “all steel” alternative design for the superstructure.

The steelwork design and details were developed in close consultation with the steelwork contractor, Rowecord Engineering Ltd, to suit its preferred method of fabrication and erection.

Judges’ Comment

s:

A strikingly elegant bridge carries a dedicated bus lane, cycleway and pedestrian route over the A483 road. The solution has a cable-stayed structure, with a single slender, sloping mast supporting an orthotropic deck. This fully meets the client’s brief to provide a landmark economically which reflects Swansea’s maritime history.

The minimised disruption to the busy road below directly resulted from the effective use of steel. A fine example of modern bridgework.