In cases like this it's worth brainstorming a bit first. After and during it might be a good idea to see what others have done with tools like the noun project (and search for broken and crane for example). Then just integrate the ideas by combining things, here I'm combing crane, broken bone and typical warning sign. YMMV.
Image 1: Quick example combining 3 different concepts
Obviously you need to do your own thinking here and my example is very quick but shows how you could approach the problem.