Holdfast Training Services Trial Blog

I recently attended an I Struct E lecture at Cardiff Uni on the Dee railway collapse in 1847. The main reason for its collapse was almost immediately obvious from a slide showing an image of the girder design. A quick sketch of a force diagram in my notebook showed, without the need for any math’s at all (hooray!), that the design was fundamentally floored (unsure if my scribbles below will make sense to anyone but me?).

The lecture went on to explain that the engineer responsible (the esteemed Robert Stephenson) had failed to recognize that by fixing the chain to the girder as he did, it was not acting as he intended but was actually exacerbating the problem he aimed to mitigate. This was the main cause of failure, along with other factors including insufficient restraint against lateral torsional buckling.

This reinforced to me the importance of understanding the very basics, understanding how and in which direction forces are acting and dare I say it the use of free body diagrams before I get carried away with any detailed cals. on any project I’m working on.

Interestingly enough, following the post collapse investigation the structural analysis that identified the floored design was conducted by Capt. (later Field Marshal) John Simmons RE, who was ‘inspector of railways’ at the time. Perhaps the PEW staff can search the archives to confirm but I like to think he was on PET(C) 001 completing his Ph 2/3 placement with Ye Olde Network Rail at the time.