the second-floor walkway from the fourth-floor walkway. This design change would be fatal. In the original design, the beams of the fourth-floor walkway had to support only the weight of the fourth-floor walkway, with the weight of the second-floor walkway supported completely by the rods. In the revised design, however, the fourth-floor beams supported both the fourth- and second-floor walkways, but were strong enough only for 30% of that load. The serious flaws of the revised design were compounded by the fact that both designs placed the bolts directly through a welded joint connecting two C-channels, the weakest structural point in the box beams. The original design was for the welds to be on the sides of the box beams, rather than on the top and bottom. Photographs of the wreckage show excessive deformations of the cross-section. During the failure, the box beams split along the weld and the nut supporting them slipped through the resulting gap, which was consistent with reports that the upper walkway at first fell several inches, after which the nut was held only by the upper side of the box beams; then the upper side of the box beams failed as well, allowing the entire walkway to fall in a cascading failure. A court order was required to retrieve the skywalk pieces from storage for examination. 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. Reports and court testimony cited a feedback loop of architects' unverified assumptions, each having believed that someone else had performed calculations and checked reinforcements but without any actual root in documentation or review channels. Onsite workers had neglected to report noticing beams bending, and instead rerouted their heavy wheelbarrows around the unsteady walkways. Jack D. Gillum would later reflect that the design flaw was so obvious that "any first-year engineering student could figure it out," if only it had been checked. Legal The Missouri Board of Architects, Professional