The Hyatt-Regency Walkway Collapse

written by:

Randy Conn, Tate Jacobitz, Paul Olsen, and Mark Rains

Introduction

On July 17, 1981 at five after seven p.m., the guests at the newly opened Hyatt Regency of Kansas City, Missouri, were enjoying a dance contest in the spacious lobby. The excitement of this contest had brought nearly 2000 spectators to watch the contest. Many of these people were on the atrium floor while some watched from the second (approximately 20 people), third, and fourth (approximately 40 people) floor suspended walkways. These walkways were suspended above the atrium of the Hyatt Regency and connected the tower to the functioning block of the hotel.

As the contest progressed, a loud "crack" was heard. This "crack" preceded the collapse of the second and fourth level walkways onto dance floor, crushing many people. This outlandish disaster resulted in 113 deaths and 186 injuries. The unfortunate event lead to a detailed and thorough investigation of the structural remains.

The investigation pinpointed the cause to be related to the design of the box beam hangers of the fourth level walkway. G. C. E. International Inc. (then known as Jack D. Gillum and Associates Ltd.), the engineering firm which designed the Hyatt Regency, did not solely design the suspended walkways and box beam hangers. Instead, the walkways were designed and built by Havens Steel Co., Kansas City, Missouri. The engineers at G. C. E. International provided the people at Havens Steel with preliminary drawings of how they wanted the walkways to be designed. Through a series of miscommunicated designs, the walkways were ultimately built differently than their originally intended design. The structural failure ultimately resulted from poor communication between the designers and the fabricators.

This article provides the reader with adequate background information to understand the structural reasons for the collapse as well as the events surrounding the design mistakes.

 

Original Design

Each walkway was to be spanned by box beams to provide a connection for the support rods. The box beams were to be constructed from American Standard MC8 X 8.5 channels joined toe to toe by continuous welds along the seams as seen in Figure 2. For the configuration of the second and fourth level walkways, a single rod design was to be used which would have passed through each fourth floor box beam and continue on to support the second floor walkway. Each box beam of the walkway was to be supported by a washer and nut which had been threaded onto the supporting rod as Figure 2 indicates. However, to support the fourth level walkway, the support rod would require threads along most of its length. In addition, the long rods would be difficult to handle during construction. Therefore, another design for the support of the second level walkway was implemented.

Figure 2. Original Design. Adapted from Marshall, R. D. et al.

Investigation of the Kansas City Hyatt Regency Walkways Collapse.

Washington, D. C.: National Bureau of Standards, 1982.

Revised Design

An alternative to the single rod supporting both the fourth and second floors was adopted which used two rods in series instead of a single rod. A sketch of the revised design is shown in Figure 3. One end of each support rod was joined to the American Standard W18 X 40 roof cross beams of the atrium ceiling. The other end continued through the box beam of the fourth floor where a washer and nut were threaded onto the end of the support rod. A second support rod was then attached to each box beam four inches in from this first rod. These support rods suspended down to support the second level walkway in a similar fashion.

 

Failure

The failure of the walkways in the Hyatt Regency Hotel was undeniably the outcome of a structural failure. Yet, upon further investigation, the structural failure was complemented by other failures. One such failure was the lack of communication between the design engineer and the steel fabricator.

 

Structural Failure

Someone once wrote an excellent paradigm which compared the original design of the Hyatt Regency atrium walkways with the design which was implemented. Suppose a long rope is hanging from a tree, and two people are holding onto the rope -- one near the top and one near the bottom. Under the conditions that (1) each person can hold their own body weight, and (2) that the tree and rope can hold both people, the structure would be stable. However, if one person was to hold onto the rope, and the other person was hanging onto the legs of the first, then the first person’s hands must hold both people’s body weights, and, thus, the grip of the top person would be more likely to fail.

Similarly, the structural point of failure of the walkways occurred at the fourth level hanger connection. The original design for the hanger rod connections, as laid-out by the design engineers, can be seen in Figure 2. This design utilized one long rod onto which the second and fourth level walkways would be attached. This would be similar to the two people hanging onto a rope separately in the paradigm. However, the structure was fabricated differently, as shown in Figure 3. With this design, the fourth level box beams would be required to hold both their own load, as well as the second floor walkway’s load. This implemented design would be similar to the second person hanging onto the first person’s legs. The first person’s grip must hold approximately twice the weight required to just hold himself up, as did the fourth level hanger rod connection.

 

Figure 3. Revised Design. Adapted from Marshall, R. D. et al.

Investigation of the Kansas City Hyatt Regency Walkways Collapse.

Washington, D. C.: National Bureau of Standards, 1982.

 Since the box beams on the fourth level were welded longitudinally in accordance with the original walkway design, they were unfit to hold the weight of both walkways. Unfortunately, the center box beam split, allowing the support rod to pull through the box beam, as can be seen in Figure 4. The nut did not part from the support rod, and thus, was not the cause of failure.

 

Communication Failure

Since the construction process includes the work and ideas of many different people, the process can become unclear, especially when meeting deadlines and budget requirements. Such a fast-paced environment stems from the concept that time is money. This concept continually drives the construction industry to seek quicker methods to transfer conceptual ideas from paper to tangible structures of concrete and steel. It has become common practice in the construction industry to begin the actual construction of a building prior to the design work being completed. The Hyatt Regency Hotel was built on this fast-track type of schedule. The main reason for the walkway collapse was not a failure of materials. It was a communication failure.

In the case of the Hyatt Regency Hotel, the structural engineer sent a sketch of the proposed walkway connections to the steel fabricator. The structural engineer had assumed that the fabricator understood that he was to design the connections himself. Since the structural drawings did not explicitly state that the walkway connections were only a preliminary sketch, the steel fabricator assumed that the sketch was a finalized drawing.

The fabricator simply copied the engineer’s preliminary sketch of the walkway connection to serve as the shop drawings. The development of the design was then completed using "fabricator’s judgment." Design by fabricator judgment selects the standard pieces: (1) as indicated on the structural drawing, (2) as prescribed by the AISI manual, or (3) under the fabricator’s discretion. The materials selected for the fabrication were standard strength, size, and grade of material, rather than what should have been used to compensate for the added stress of the altered design. Such neglections can have grave results.

The most glaring mistake in this entire chain of events was that the structural engineer did not review the final design. As can be seen from the evidence, the real failure that caused the collapse of the Hyatt Regency walkways was actually a failure of communication in the design phase of the project. As a result of the disaster, the two engineers from G. C. E. International lost their professional engineering licenses in the state of Missouri. These engineers were Jack D. Gillum, the engineer of record, and Daniel M. Duncan, the project engineer.

 

The purpose of including this paper in The Moment is twofold. First, to provide civil engineering students with the historical facts concerning this catastrophic structural failure. But more importantly, to remind the civil engineering student of the responsibility associated with a civil engineering profession.