Rusting bridges - superficial damage?

Obviously a lot of rust damage is just superficial and doesn’t affect structural integrity but it must be a full time job to regularly check every bridge, particularly for damage to hidden internal load bearing elements.
How often would each bridge be examined by structual engineers, is this carried out by NR or external consultants?

edit: apologies should of said this was at Bradford on Avon - station was behind me.

There are regular structural inspections but I don't know the details. I'd be very surprised if NR wasn't aware of that very visible defect (Where is it? Looks a bit GWR?).

One were rust caused a major incident that could have been far worse was at Stewarton in 2009: http://www.railwaysarchive.co.uk/eventsummary.php?eventID=6558

The immediate cause of the derailment was the collapse of the bridge (known as Bridge 88) that followed the catastrophic structural failure of its east and centre
main girders. Heavy corrosion had so significantly weakened these main girders that they were no longer able to carry the loading from trains that were permitted to run over the bridge.

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A major contributory factor was that the corroded areas were not visible and no "intrusive" inspection was done. There's a fair bit in the report about the inspection process (paragraph 49 onwards) although I hope it's been improved since then!

There have also been various accidents and near-misses due to "scouring" of bridge foundations by fast-moving water.

4 miles north of Preston over the WCML. Carries Woodplumpton Road/Newsham Hall Lane. Where they have added extra height for electrification it seems to have induced corrosion!!

The standard for NR structures requires a visual exam to be carried out yearly and a detailed exam carried out every six years, unless a structure has specific issues that require a greater or lesser frequency. Exams are carried out by Network Rail’s contractors (Amey in my part of the world).

A very interesting story of the rebuilding of the (five, I think) underbridges on the extension to Broadway GWSR preserved line can be found at the GWSR unofficial blog links on its website. What struck me was in how much essentially good condition, most were. None had to be replaced, this after many decades of total neglect and they were nearly all metal, not stone. It still needed a seven figure sum to put them right, but still, most impressive.

HowardGWR said:

A very interesting story of the rebuilding of the (five, I think) underbridges on the extension to Broadway GWSR preserved line can be found at the GWSR unofficial blog links on its website. What struck me was in how much essentially good condition, most were. None had to be replaced, this after many decades of total neglect and they were nearly all metal, not stone. It still needed a seven figure sum to put them right, but still, most impressive.

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You just have to love those Victorian Engineers - especially IKB

edwin_m said:

There are regular structural inspections but I don't know the details. I'd be very surprised if NR wasn't aware of that very visible defect (Where is it? Looks a bit GWR?).

One were rust caused a major incident that could have been far worse was at Stewarton in 2009: http://www.railwaysarchive.co.uk/eventsummary.php?eventID=6558

A major contributory factor was that the corroded areas were not visible and no "intrusive" inspection was done. There's a fair bit in the report about the inspection process (paragraph 49 onwards) although I hope it's been improved since then!

There have also been various accidents and near-misses due to "scouring" of bridge foundations by fast-moving water.

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steve2525 said:

Obviously a lot of rust damage is just superficial and doesn’t affect structural integrity but it must be a full time job to regularly check every bridge, particularly for damage to hidden internal load bearing elements.
How often would each bridge be examined by structual engineers, is this carried out by NR or external consultants?

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GRALISTAIR said:

You just have to love those Victorian Engineers - especially IKB

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Thanks for the comments, yes agree the original builders did a great job.

steve2525 said:

Obviously a lot of rust damage is just superficial and doesn’t affect structural integrity but it must be a full time job to regularly check every bridge, particularly for damage to hidden internal load bearing elements.
How often would each bridge be examined by structual engineers, is this carried out by NR or external consultants?

edit: apologies should of said this was at Bradford on Avon - station was behind me.

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I think asset management must be a difficult area to work in, because budgets are tight and you have to use professional judgment to decide what should be repaired and what should be allowed to deteriorate.

If I worked in asset management, I think I'd start by putting in a bulk order for Waxoyl oily paint and smothering all my metal assets like these bridges. It wouldn't fix the damage but I bet it would slow the deterioration down a lot.

[Slightly off topic]
I am keeping the name Isambard on the list for any future cat that adopts me.
Got a lot of feedback about my recent cat whom I named Innish (and then renamed feral cat Oplympuss to Outish.]

GRALISTAIR said:

You just have to love those Victorian Engineers - especially IKB

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Totally agree!
Incidentally the GCR has had to repair at least two of it's overbridges (at Swithland) due to rust and now it is having to do the same sort of work on the canal bridge, North of the engine shed.

GRALISTAIR said:

You just have to love those Victorian Engineers - especially IKB

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In the case of the GWSR, we are talking Edwardian engineers. The Honeybourne-Cheltenham route was not built until the 1900s and while the bridges may have been sound, you can't say the same for the embankments.

steve2525 said:

Obviously a lot of rust damage is just superficial and doesn’t affect structural integrity but it must be a full time job to regularly check every bridge, particularly for damage to hidden internal load bearing elements.
How often would each bridge be examined by structual engineers, is this carried out by NR or external consultants?

edit: apologies should of said this was at Bradford on Avon - station was behind me.

View attachment 52120

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In addition to annual visual and six-yearly detailed inspections, structural assessments of bridges are also undertaken periodically, although these are often decades apart. Assessments analyse the load carrying capacity of a bridge and take into account the condition of the structure. If an assessment show that a bridge has insufficient capacity for the type of traffic it carries then it may need to be strengthened or have weight restrictions imposed to ensure that it's safe.

In the case of this bridge (St Margaret's Street, I believe) the carriageway appears to have been restricted to a single lane with bollards protecting the footway and parapet closest to the camera. This might indicate that the bridge's assessed capacity is limited by its poor condition, particularly over the edge girder. It's also apparent from the photo that the corroded web of the edge girder has been repaired with additional steel plates in the distant past. This all suggests that someone, somewhere is aware of its condition.

Modern railway bridges are designed without 'hidden critical elements' so that all the important bits can be inspected quickly and safely.

You're right though, monitoring the condition of every structure and keeping them safe is an enormous undertaking, especially given the age of our railway infrastructure.