The Hotel Walkway Change Nobody Checked

On July 17th, 1981, two suspended walkways full of people fell across the lobby of the Hyatt Regency in Kansas City, Missouri. The federal report counts 113 dead and 186 injured. It wasn't the crowd: the connection that failed first was carrying 53 percent of what the building code required, and less than a third of the load it should have been able to hold. The National Bureau of Standards traced the collapse to a change on the shop drawings, where one continuous steel hanger rod became two, and to a connection that never met the code even before the change. This is the full story of the Hyatt Regency walkway collapse, told from the official NBS report (Building Science Series 143, May 1982): how the walkways were designed and hung from the roof, what the building code asked of the box beam and rod connections, what the shop drawings changed, the three stamps and the missing calculations, the evening itself, the fall connection by connection, the tests on sixty-seven box beams, the arithmetic in kips, and the cause in the investigators' own words. A final chapter covers what the report does not say about who proposed and approved the change and what the hearings and courts decided, drawn from a university ethics guide that quotes the 1985 Missouri hearing decision, and marked as secondary. Every number on screen comes from the report, with its page. Full sources list: https://tinyurl.com/3zxjv2b7 Chapters 0:00 The Hyatt Regency, July 17, 1981 0:39 The hotel and its three walkways 1:26 How the walkways were hung 2:21 What the building code asked for 3:27 The change on the shop drawings 4:59 Three stamps and no calculation 5:39 Built in 1979 6:37 The evening of July 17 7:31 The fall, connection by connection 8:51 The night 9:35 The federal investigation 10:50 Ruling out the crowd 11:30 The arithmetic, in kips 12:26 Even the original was too weak 13:09 The cause, in the report's words 14:08 Who decided: what we know and what we don't 15:38 What changed #HyattRegency #WalkwayCollapse #Engineering