the original design, each nut had to support the walkway directly above it and any people on that walkway. The subtle change no one had noticed was that, with the modification, the bottom walkway was now directly suspended from the top walkway. So, as well as supporting its own weight and the people on it, this top walkway also had the bottom walkway hanging from it. The nuts which previously had to hold only the top walkway were now holding up the entire structure.
