Carshalton Beeches Railway station Footbridge

Project Overview

During May 2016, RSI were commissioned by BAM Nuttall to undertake a Special Inspection and various NDT works to Carshalton Beeches single span hipped lattice footbridge in order to assist in a full assessment of the structure. RSI’s bridge engineers were able to advise the client on the best approach / methods available in order to determine the section thickness and condition of both the steel chords and the reinforced concrete deck. The tests comprised of the following:

  • Delamination survey of reinforced concrete deck using lump hammer
  • Half cell test grids at 500mm spacing’s to soffit of deck and staircases
  • Dust drilling to obtain samples for subsequent chloride ion contamination
  • Main reinforcement cover survey
  • Concrete resistivity measurement undertaken using a 2 probe test method
  • In‐situ test for depth of carbonation on freshly broken concrete surface
  • Paint adhesion testing by cross cuts
  • Paint sampling for harmful substances (Lead & chromium)
  • Ultrasonic weld testing to steel chords
  • Close visual inspection of welds via x15 illuminated magnifier
  • Dimension survey

All obtained dust and paint samples were retained, sealed and uniquely labelled in polythene bags, then returned to our UKAS accredited laboratory for chemical analysis.

Inspection access was in the form of a GRP scaffold tower erected by our in house PASMA trained technicians. Once all the information was collated, a full comprehensive report was produced compiling of Auto CAD drawings with developed views of tested elements, half cell contour maps to assist in a rapid assessment of the tested areas, clear photographic evidence of tests completed and a UKAS accredited
laboratory report for sampling results.

RSI staff utilised in‐house equipment to complete the works and comprised of the following :‐

  • GRP scaffold tower
  • Hilti PS250 Cover meter (Ferroscan)
  • Hilti TE‐60 hammer drill with 20MM drill bit
  • Elcometer half cell potential monitor and electrode
  • Resistivity 2 probe kit
  • Cross cut adhesion test equipment
  • x15 illuminated magnifier
  • Sitescan 150
  • All required PPE

The works were completed within a controlled rail possession on a limited time scale and to the clients brief. All testing was carried out following our inhouse
testing procedures and in accordance with BA35/90.

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