The most recent SCOSS and CROSS newsletter has a headline that is a slap in the face, and almost certainly a deserved one. Report number 858 is “Repeating the same mistakes” and it describes areas where engineers are literally dong that. The whole purpose of forensic investigations, from the engineers’ perspective, is to understand what went wrong so that we can try to prevent it from happening again. When I wrote about learning from failure, this is exactly what I had in mind.
The specific examples in the newsletter aren’t actually important unless you’re designing one of the categories mentioned. But it’s horrifying that such basic items are being designed improperly in 2019. People have been sitting beams on masonry walls since before written history, and have been sitting iron and steel beams on masonry since the 1700s. There is no excuse for beam bearings (“padstones” in the UK terminology) to not be designed properly if we (the design and construction community) make the slightest claim to learning from the past.
So how does it happen? One issue is nicely summarized: “Perhaps it is worth bearing in mind that if a career lasts 40 years, then around 2.5% of expertise leaves the industry each year, to be replaced by young entrants – therefore we all must be active in our learning and the promulgation of learning.” In other words, it is the responsibility of young engineers to learn what they need to know after they leave school and it is the responsibility of experienced engineers to teach them.
There’s another, more disturbing possibility, best summarized as “over-familiarity.” People in general are good at finding patterns, and engineers are probably self-selected to be better at that skill than most. If you’ve designed hundreds of beams, it is easy to fall into a pattern of giving the bearing conditions on masonry walls only cursory looks. After all, you’ve seen it all before. Except you haven’t. I have seen many buildings that look similar – I’ve worked on a lot of rowhouses, and a lot of 1910s loft buildings, and a lot of 1920 apartment houses, and so on – and they’re never identical. They are similar, and therefore that every project requires its own investigation. The same thing is true for new-building design: there are hundreds of variables that get tweaked from one project to the next, so similar designs are never identical.
Repetition is how we learn, but it also can be misleading. We need to be aware of this as we learn and teach. I’ll end with Mark Twain on the topic of learning too much from experience: “If a cat sits on a hot stove, that cat won’t sit on a hot stove again. That cat won’t sit on a cold stove either. That cat just don’t like stoves.”
