We perform a good many fire escape inspections and design for repairs, here in Seattle. There are plenty, with all the old brick buildings. Our job is to verify that every escape can hold the necessary load of people escaping from a fire, should one occur.
We work with a contractor, who does this by hooking a come-along and a load cell to the structure, and pulling with a force equivalent to that weight. We pull for at least ten minutes, and if there is any movement, we stop the test and specify repairs to make it stronger. Then, of course, test again. We have not actually encountered a failure to date.