Landmark link - architectural design of a cable stay bridge in Salford, England - includes plans

Architectural Review, The, March, 1996 by Dennis Sharp

Trinity Bridge was inaugurated in September last year. It spans the 36 m wide River Irwell linking the underused Chapel Wharf area of Salford with a lively edge of Manchester's business district off Deansgate.

The new bridge represents a move away f rom the bent tube structures and concrete support design that have preoccupied Santiago Calatrava in recent years. Instead, it concentrates on an exploration of lightweight materials and the aesthetics of structural and visual tension. As the design developed, Calatrava drew inspiration from the linear sculptural constructions of Naum Gabo and the spatial experiments of Antoine Pevsner. The result, however, is unlike the finished work of either of these sculptors in terms of scale or in the way it solves - with an efficient and economic symmetrical plan shape - the need to create a new landmark in a drab environment, and a simple crossing.

Linking a large redevelopment site on the Salford side, the bridge connects a new car parking area to the edge of Manchester's thriving business district. Along with local initiatives in both cities, Salford is providing a focus for the potential regeneration of a completely unexploited inner city area.

The cable stay bridge design was chosen (a simpler box girder based alternative scheme omitted the pylon and cable stays) because of its symbolic potential. Shot through with complex tensions, the concept is built up three dimensionally into a fecund design which allows the long stalk-like plan shape of the curved stressed deck to land sensitively on the Manchester bank, like a visitor from another planet. Indeed, at one moment in its design there was some discussion about the possibility of the narrower end of the bridge just hovering 100 mm above the bank on the Manchester side. This cleavage would have allowed the whole structure to have a sense of movement, freed from the rigid connections demanded by current design regulations.

The bridge springs from the Salford side of the river reaching over towards Deansgate from its tall, sloping and highly visible white painted steel pylon, 37 m high. The total length of the bridge is 67 m long. The minimum width at the Manchester end is 6 m and on the Salford side approximately 11 m. The huge white painted steel pylon, which rises from an in situ concrete base containing a short staircase, holds the subtly curved spanning bridge deck (which is pitched at 1:18) and the spiralling entry ramps by means of taut stainless steel cable stays, giving the whole spectacular design its tense, dynamic sculptural profile.

The concrete abutments and foundations on either side of the river were also cast on site. The ramps connect with the abutments which have moveable supports in the direction of the main span axis. The deck, which is made from an independent torsionally stiffened hollow box girder beam, was lifted on site from the Salford side in three main sections. The deck and pylon were manufactured in Bilbao, Spain and assembled on site. The stainless steel stays were positioned and post-tensioned on completion by the main contractor after final computer verification of lengths.

For Calatrava, bridges always have a special influence on local environments. Not merely utilitarian objects set in the urban scene, they have a power to heal past disputes and provide new opportunities. With the Bach de Roda bridge in Barcelona, two distinct communities were brought together. Here, this new bridge is seen as a reconciling link between the rival cities of Salford and Manchester. At night its symbolic mission is further enhanced, when the integral lighting scheme comes into play. The white painted pylon is lit up as well as the underside of the bridge which reflect light onto the river surface. A further stage could see the clean up of the murky Irwell too.