Structural change

Events and disputed communications between G.C.E. engineers and Havens resulted in a design change from a single to a double hanger rod box beam connection for use at the fourth floor walkways. The fabricator requested this change to avoid threading the entire rod. They made the change, and the contract's Shop Drawing 30 and Erection Drawing E-3 were changed.

On February 16, 1979, G.C.E. received 42 shop drawings (including the revised Shop Drawing 30 and Erection Drawing E-3). On February 26, 1979, G.C.E. returned the drawings to Havens, stamped with Gillum's engineering review seal, authorizing construction. The fabricator (Havens) built the walkways in compliance with the directions contained in the structural drawings, as interpreted by the shop drawings, with regard to these hangers. In addition, Havens followed the American Institute of Steel Construction (AISC) guidelines and standards for the actual design of steel-to- steel connections by steel fabricators.

As a precedent for the Hyatt case, the Guide to Investigation of Structural Failure's Section 4.5, "Failure Causes Classified by Connection Type," states that:

Overall collapses resulting from connection failures have occurred only in structures with few or no redundancies. Where low-strength connections have been repeated, the failure of one has lead to failure of neighboring connections and a progressive collapse has occurred. The primary causes of connection failures are:

1. Improper design due to lack of consideration of all forces acting on a connection, especially
those associated with volume changes.

2. Improper design utilizing abrupt section changes, resulting in stress concentrations.

3. Insufficient provisions for rotation and movement.

4. Improper preparation of mating surfaces and installation of connections.

5. Degradation of materials in a connection.

6. Lack of consideration of large residual stresses resulting from manufacture or fabrication.

Roof collapse

On October 14, 1979, part of the atrium roof collapsed while the hotel was under construction. As a result, the owner called in the inspection team. The inspection team's contract dealt primarily with the investigation of the cause of the roof collapse and created no obligation to check any engineering or design work beyond the scope of their investigation and contract.

In addition to the inspection team, the owner retained, on October 16, 1979, an independent engineering firm, Seiden-Page, to investigate the cause of the atrium roof collapse. On October 20, 1979, G.C.E.'s Gillum wrote the owner, stating that he was undertaking both an atrium collapse investigation as well as a thorough design check of all the members comprising the atrium roof. G.C.E. promised to check all steel connections in the structures, not just those found in the roof.

From October-November, 1979, various reports were sent from G.C.E. to the owner and architect, assuring the overall safety of the entire atrium. In addition to the reports, meetings were held between the owner, architect and G.C.E.

In July of 1980, the construction was complete, and the Kansas City Hyatt Regency Hotel was open for business.

Walkway collapse

Just one year later, on July 17, 1981, the box beams resting on the supporting rod nuts and washers were deformed, so that the box beam resting on the nuts and washers on the rods could no longer hold up the load. The box beams (and walkways) separated from the ceiling rods and the fourth and second floor walkways across the atrium of the Hyatt Regency Hotel collapsed, killing 114 and injuring in excess of 200 others.

One investigation report gave the following summary:

The Hyatt Regency consists of three main sections: a 40-story tower section, a function block, and a connecting atrium. The atrium is a large open area, approximately 117 ft (36 m) by 145 ft (44 m) in plan and 50 ft (15 m) high. Three suspended walkways span the atrium at the second, third, and fourth floor levels. These walkways connected the tower section and the function block. The third floor walkway was independently suspended from the atrium roof trusses while the second floor walkway was suspended from the fourth floor walkway, which in turn was suspended from the roof framing.

In the collapse, the second and fourth floor walkways fell to the atrium first floor with the fourth floor walkway coming to rest on top of the second. Most of those killed or injured were either on the atrium first floor level or on the second floor walkway. The third floor walkway was not involved in the collapse.

Aftermath

Photographs taken by Dr. Lee Lowery, Jr., P.E., shortly after the collapse: