arches

This pic comes from Network rail's Bridge Condition Marking Index manual. The caption says that there are horizontal and vertical cracks more than10mm wide, severity rating O and L respectively.
But what about the fact that the cracks taper? If you look at the taper you can see that the cracks have been caused by expansion of something exactly where the patch is. I suspect that the damage has been caused by the crack. Two vital lessons not learned by the writer of the manual let alone the many hundreds of engineers and inspectors who learn from the book.

As an industry, we must do better.

Here are two pictures of a railway bridge in Bristol. They were taken two 8 years apart. That is not a long time in arch bridge terms. Spectacular deterioration that needs to be addressed on three levels.
1) How are such faults best detected, recorded and dealt with
2) what causes such damage and how can we predict it
3) How can we train engineers and inspectors to recognise the scale of the problem.