Havens Steel Company had manufactured the rods, and they objected that the whole rod below the fourth floor would have to be threaded in order to screw on the n

Havens Steel Company had manufactured the rods, and they objected that the whole rod below the fourth floor would have to be threaded in order to screw on the nuts to hold the fourth-floor walkway in place. These threads would be subject to damage as the fourth-floor structure was hoisted into place. Havens Steel, therefore, proposed that two separate and offset sets of rods be used: the first set suspending the fourth-floor walkway from the ceiling, and the second set suspending the second-floor walkway from the fourth-floor walkway. Investigators concluded that the underlying problem was a lack of proper communication between Jack D. Gillum and Associates and Havens Steel. In particular, the drawings prepared by Gillum and Associates were only preliminary sketches, but Havens Steel interpreted them as finalized drawings. Gillum and Associates failed to review the initial design thoroughly and engineer Daniel M. Duncan accepted Havens Steel's proposed plan via a phone call without performing necessary calculations or viewing sketches that would have revealed its serious intrinsic flaws—in particular, doubling the load on the fourth-floor beams. -- https://en.wikipedia.org/wiki/Hyatt_Regency_walkway_collapse https://en.wikipedia.org/wiki/Hyatt_Regency_walkway_collapse