I work with professionals that repair the infrastructure that gets damaged from people travelling within and through the City every day. It is easy to overlook this work because often we're responding within hours of a crash to make the street or sidewalk safe for everyone that comes across the incident.
As an engineer, I never learned much about maintenance. Calculations about how you deal with equipment that has been damaged are difficult (messy), we can't make a lot of assumptions that we can count on. We're trained to work on projects where we start fresh and you have a blank slate. That's not possible with the real world day to day maintenance, so we do what we can with what is available in some cases.
The repair that these professionals in the field make are impressive when you think about the wide variety of things they come across. Here's just one example.
We don't have this type of ornamental poles at the ready, so we had to take a few days to order the pole and replace it the following week. The challenge with this ornamental pole is that the rods that are part of the foundation are over sixty years old (some of them are from the 1920s). Not exactly your perfect world engineering calculation.