being critically reintegrated into the present.’ 15 The setting of the bridge is beautiful, viewed along the river it appeared to be a rural site, and is designated a site of special scientific interest. From Ballingdon Street, however, the bridge appears to be in an urban context. The logistical constraints of reconstruction included the need to keep the traffic flowing – achieved via a moveable bailey bridge; the safe temporary support of services; and the need to keep the river Stour flowing and unpolluted. The project was specified and constructed on a sustainable basis, the earlier bridge was recycled, and the wild life and river environment was carefully protected during the construction. It was vital to respect the ecology of the site during the construction process and in the completed project. The soffit of the new bridge incorporates bat bricks, which provide nesting sites for pipistrelle bats and a timber otter run on one bank. The bats need the darkness under the bridge whereas the otters are afraid of it, and if an otter run is not provided they will cross the road and risk becoming road kill, which is unacceptable in contemporary Britain. The landscaping of the Boathouse Hotel, was reinstated on completion, including daffodils and river irises. The materials of the new bridge were carefully selected to respond to the local context and fulfil the performance requirements of a road bridge, which combine engineering, urban design and architecture. The primary structure is formed from precast concrete, and the mix was selected to match the
limestone of All Saints, a twelfth century Norman Church. This palette of materials also included granite, stainless steel, aluminium and English Oak. Even the aggregate within the tarmac of the roadway was agreed with the planning officer. The design of the new bridge is visually calm, respecting the historic context. Designed using a research-based evolutionary technique the bridge has an everchanging and site-specific geometry, Fig 11. Ballingdon Bridge was conceived as a post-Ford and post-Egan project. John Egan’s report Rethinking Construction (1998) with its advocation of standardisation was factually out of date - the construction industry had started to engage with the use of digital fabrication to deliver non-standard or project-specific components. The precast units were manufactured by Buchan in timber moulds, which were beautifully crafted from the architect’s digital geometry. The moulds were in essence hand crafted using Jelutong (Dyera costulata) and checked with laser-cut templates. Although only a precursor of the final architecture the moulds were very beautiful forms. Buchan used a total of seventeen pattern makers and carpenters to fabricate the moulds, working to an accuracy of ±2mm. The design for Ballingdon Bridge has a gently curvilinear profile and a dynamically morphed soffit. Within this everchanging geometry no two adjacent sections are the same. It was designed using an iterative lofting technique. The geometry morphs from slice to slice. The design files were a common digital resource for the complete design team. Without this digital geometry, generated by
the architects, it would have been very difficult to realise this bridge. Ballingdon Bridge is an example of the holistic digital delivery of a project with the architect at the centre of the process. This is the opposite of the marginalisation experienced by many architects in the recent past. The balustrade was designed to be visually open so that the views of the landscape are as uninterrupted as possible. It is capable of arresting a 42 tonne truck yet appears to be an elegant pedestrian handrail, its strength being achieved by a combination of stainless steel castings, stainless steel wires and purpose made aluminium extrusions. The illuminated bollards were designed for the project to avoid the need to use lampposts on the bridge. Cased in anodised aluminium, the core of the bollards is a galvanised circular hollow steel section, which will stop cars from crossing the pavement but shear off if hit by larger vehicles. The top rail of the balustrade is a combination of extruded aluminium and English oak. This point of human contact is key to its design; to a pedestrian the vehicular safety role of the balustrade is intended to be an unseen quality. The enlarged oak walkways create a generous provision for pedestrians to enjoy the views of the river and meadows. People enjoying the river and the urban spaces of Ballingdon and Sudbury are the priority within the design of this road bridge, Fig 12. By careful study of the construction and phasing of the bridge, and extensive prefabrication, disruption to Sudbury and Ballingdon was minimised and two-way traffic on
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