This project involved strengthening and detailed maintenance repairs to a mainly wrought iron Grade 2* listed arch structure with five 45 metre-long spans carrying a two-track railway over the River Thames. Built in 1863, 150 years of rail traffic in a harsh environment – and today carrying about 18 trains per hour – had taken its toll.
The tender came out with a strengthening design completed for implementation. Crouch Waterfall reviewed the strengthening proposals and identified that the strengthening could be designed more practically and more economically. The primary issue with this was that the tender period was short and there was no allowance for design within the construction programme. As such, Crouch Waterfall analysed the complex structure and produced a revised preliminary strengthening design within the tender period to allow Kier to produce a more economical bid. Network Rail awarded the team a contract from 2013 to design and repair, strengthen and apply a protective coating system to the bridge to extend its life by 25 years.
Due to the reduction in possession requirements and the improvement in implementing the strengthening design, a short period was available within the programme to allow the design to be finalised, independently checked and approved by Network Rail prior to site works to begin. The whole process to final approval only took 4 months, much of which was approval time and coincided with the site mobilisation period.
Crouch Waterfall provided an on-site presence through-out the construction period which included a detailed condition survey of all of the 9,000 structural elements and their connections to accurately identify any defects and design repair solutions to be implemented during normal train operations.
Thanks to this approach, it will be possible to resurvey this bridge in the future and make a direct visual comparison with 2015.
The project won an award for Civil Engineering Achievement of the Year presented at the NATIONAL RAIL AWARDS 2016 and a the National Railway Heritage NRCG Restoration Award 2015.