Bersted Crossing footbridge is a good example of a wrought iron, lattice girder railway structure from the end of the Victorian era. The poor aesthetic condition of the bridge led to public perception that it required replacement. A sympathetic restoration scheme taking into account the unmodified nature of the wrought iron was shown to be economical and was carried with no disruption to train services. The work received a commendation as part of the 2005 Historic Bridge and Infrastructure awards. This briefing article describes the background to the structure and the work that took place to restore it.
1. INTRODUCTION
Bersted Crossing footbridge crosses the Barnham Junction to Bognor Regis railway line outside Bognor Regis station. The hipped profile, wrought iron, lattice girder construction is typical of many south-coast railway footbridges. This example has not been modified since original construction and although the bridge was in poor aesthetic condition the period features remained in good structural condition. This briefing article describes the refurbishment work undertaken by asset owner Network Rail. The work received a commendation as part of the 2005 Historic Bridge and Infrastructure awards.
2. STRUCTURE DETAILS
The structure is formed of an 8 m central span across the double-track railway and two 7 m side spans with stairs to ground level. Timber decking spans between the combined cross-girder and outrigger bracing for the lattice truss girders. Each timber stair tread is supported on cleats riveted to the bottom chord of the side span trusses. The superstructure is supported on cast iron columns (Fig. 1).
3. HISTORY
The London, Brighton and South Coast Railway (LB&SCR) was formed in 1846 by the amalgamation of the London & Brighton Railway and the London & Croydon Railway. The branch line into Bognor Regis opened in 1864. Bersted Crossing footbridge is located just 250 m from the station terminus where the buildings and canopies are listed structures.
The footbridge was commissioned by LB&SCR and although the exact date of construction is unknown, it is believed to be around 1890. This corresponds with the period that Henry Young & Co (engineers for the bridge) operated from their iron works in Ecclestone Street, Pimlico (1871–1900). Alongside bridge materials for the expansion of the railway this company produced statues and decorative castings which now form part of London's architecture including the lamp standards along Chelsea Embankment and the sphinxes for Cleopatra's Needle on Victoria Embankment.
The footbridge lies in a residential area and is an important local thoroughfare providing a crossing point for a large catchment area bounded by the railway and a busy dual carriageway A road. Despite being in good structural condition, the footbridge had been the subject of public complaints over recent years. These mainly related to the general appearance of the bridge and the public perception that it was at the end of its life. There had been requests from local residents for a new footbridge to replace it (Fig. 2).
Routine inspection and maintenance ensured the structure was fit for purpose and included little more than localised timber repairs and minor repairs to the stair cleats. An assessment of the structure was carried out in 2001 to the railway assessment standard RT/CE/C/0151 with the truss analysed as a pinconnected plane frame and the cross-girders and timber decking modelled as simply supported beams. This confirmed the bridge had adequate load-carrying capacity and although there was widespread breakdown of the paint system there was very little corrosion or lamination of the wrought iron.
4. OPTIONS
Various options were considered as part of the ongoing asset management of the structure including the removal of a foot crossing at this location, reconstruction, ongoing routine maintenance leading to future reconstruction or restoration of the existing structure.
It was clear that this footbridge, although similar in design to many in the south of England, stood out as being unmodified, with period features intact and in better structural condition. In particular, the levels of corrosion were far less than other footbridges in similar coastal environments (especially early steel bridges of the same overall design). The minimal amount of repairs required meant that prolonging the life of the footbridge through sympathetic restoration was not only the most economically viable option but also important if a good example of a historic railway structure was to be retained.
5. TEMPORARY CROSSING
Throughout the duration of the works members of the public were segregated via a temporary footbridge. This ensured continued access across the railway for pedestrians and also reduced health and safety risks to members of the public from the work site. Erection of the temporary bridge and encapsulation of the work site were carried out during ‘night-normal’ possessions with no disruption to train services.
6. SUPERSTRUCTURE REPAIRS
Previous repairs to the structural elements of the footbridge were minimal and this was something that set this structure apart from others of this type. The priority was to minimise replacement of the original wrought iron and reduce the visual impact of any repair work carried out. Repairs were confined to one cross-girder, a local repair to one of the lattice members and a small number of stair cleats. Repairs were made using steel sections which closely matched the dimensions of the original wrought iron members. Fig. 3 shows a close-up of the completed lattice work in the main span. Decayed deck timbers were also replaced. The original cast iron newel post and renewed deck timbers can be seen in Fig. 4.
7. PREPARATION AND PAINTING
The contractor elected to carry out surface preparation using manually operated power tools (needle guns). This method was labour intensive and required a high level of supervision but was chosen due to the open nature of the lattice girders and to minimise damage to the wrought iron.
The paint system was micaceous iron oxide consisting of a primer, intermediate coat and high-build decorative top coat conforming to RT/CE/S/039.2 Application was in accordance with RT/CE/C/002,3 in a colour scheme chosen to match that of the listed station buildings at Bognor Regis (Fig. 5).
The work was completed in just eight weeks with no disruption to train services and was carried out by BCM Construction, under the Network Rail Sussex area structures maintenance contract.
Total cost, including the provision of the temporary footbridge was £100 000.
The project was entered for the Historic Bridge and Infrastructure Awards to show that, given the right circumstances, preservation of heritage structures can be an economical solution for asset owners. The project received a commendation, with the judges commenting ‘A refreshingly low-tech restoration solution was found, when it could have been so easy to have lost this attractive little structure.’
8. CONCLUSION
Bersted Crossing is a good example of a wrought iron lattice girder railway footbridge with almost no alterations since original construction. The bridge was structurally adequate but poor aesthetic condition led to public perception that the footbridge required replacement.
A sympathetic scheme to restore the structure was carried out taking into account the unmodified nature of the bridge and its proximity to listed structures. The project was economical, the life of this structure has been prolonged, and major maintenance will not be required for many years.
