Patrick Barry

Engineer, Bill Harvey Associates

Patrick Barry is a bridge designer, with interests in research, workflow automation, green infrastructure and historic structures. He provides consultancy services through Bill Harvey Associates Ltd (BHAL) and through Obvis Ltd develops, markets and supports Archie-M, the de-facto standard masonry bridge assessment software.

My Sessions at Day 2

Thursday 11 March 2027

11:05

Is It Safe to Remove Those Bars? Justifying Removal of WWII Modifications to Foord Road Viaduct, Folkestone

11:05 - 11:25

During WWII, steel tie bars were installed on William Cubitt’s 1840s Foord Road Viaduct to guard against progressive collapse if a bomb destroyed a span. Decades later, corrosion of the bars and supporting metalwork posed a growing public safety risk, but before they could be removed, Bill Harvey Associates, Robert Bird Group, and Accolade Measurement had to answer a deceptively simple question for Southern Renewal Enterprise: do the bars influence how the viaduct behaves?

The presentation will cover:

  • The viaduct’s history and the uncertainties in its construction, including original drawings that don’t match reality, the wartime threat that prompted the tie system and service load damage present today.
  • Why the bars couldn’t simply be removed: although never intended to carry load, stiff load paths attract it, and their influence on service behaviour under live load mattered more than any effect on ultimate capacity
  • A measurement approach using timetabled trains at line speed, with high-frequency, high-resolution laser sensors 20 m up, and custom signal processing to detect sub-millimeter movements hidden in noisy data and against temperature effects
  • The before-and-after results from a trial bar removal, which showed a measurable but small change in behaviour, giving justified confidence that removal could proceed

Speakers