On July 17, 1981, the walkways on the second, third, and fourth floors of the Hyatt Regency hotel in Kansas City collapsed during a tea dance, killing 114 people and injuring over 200. The collapse was caused by a flawed design change where two sets of tie rods were used instead of one continuous set, doubling the load on the weakened connection points. An investigation found the revised design could only support 30% of the required load. The disaster remains studied for its engineering ethics failures and communication errors between the architect and contractor that led to the fatal design flaws.

1. Kansas City, Missouri
HYATT REGENCY WALKWAY
COLLAPSE

2. Hyatt RegencyWalkway Collapse
 The Hyatt Regency hotel walkway collapse was a
major disaster that occurred on July 17, 1981 in
Kansas City, Missouri, United States, killing 114
people and injuring more than 200 others during a
tea dance.
 At the time it was the deadliest structural collapse
in U.S. history.

3. Background
 Construction on the 40-story Hyatt Regency
Crown Center began in 1978, and the hotel opened
on July 1, 1980 after construction delays including
an incident on October 14, 1979, when 2,700
square feet of the atrium roof collapsed because
one of the roof connection on the north end of the
atrium failed.
 The building was part of a master plan devised by
Edward Larrabee Barnes and specifically designed
by the newly created architect firm PBNDML.
 It was Missouri’s tallest building.

4. Background
 The collapse was the second major structural
failure in Kansas City in a little more than two
years.
 On June 4, 1979, the roof of the then-empty
Kemper Arena in Kansas City had collapsed
without loss of life.
 The architects and engineering firms at the two
collapses were different.

5. Background
 One of the defining features of the hotel was its
lobby, which featured a multistory atrium crossed
by suspended concrete walkways on the second,
third, and fourth levels, with the fourth level
walkway directly above the second level walkway.

6. Kansas City, Missouri
DISASTER
A major cause of
fatalities was the landing
of the concrete 4th floor
walkway onto the
crowded 2nd floor
walkway, both seen here.

7. Disaster
 On July 17, 1981, approximately 2,000 people had
gathered in the atrium to participate in and watch a
dance contest.
 Dozens stood on the walkways.
 At 7:05 PM, the walkways on the second, third, and
fourth floor were packed with visitors as they watched
over the active lobby, which was also full of people.
 The fourth floor bridge was suspended directly over
the second floor bridge, with the third floor walkway
set off to the side several meters away from the other
two.

8. Disaster
 Construction difficulties led to a subtle but flawed
design change that doubled the load on the
connection between the fourth floor walkway
support beams and the tie rods carrying the weight
of both walkways.
 This new design could barely handle the dead load
weight of the structure itself, much less the weight
of the spectators standing on it.
 The connection failed and both walkways crashed
on top of the other and then into the lobby below.

10. Difference between the design and construction of the walkway support
WALKWAY SUPPORT SYSTEM

14. View of the 4th floor support beam which fell, together with support rod
SUPPORT BEAM WHICH FELL

16. Viewof the Lobby Floor

18. INVESTIGATION

19. Investigation
 Three days after the disaster, Wayne Lischka, a
structural engineer hired by The Kansas City Star
newspaper, discovered a significant change in the
design of the walkways.
 Coverage of the event later earned the Star and its
sister publication the Kansas City Times a Pulitzer
Prize for local news reporting in 1982.

20. Investigation
 The two walkways were suspended from a set of steel
tie rods, with the second floor walkway hanging
directly underneath the fourth floor walkway.
 The walkway platform was supported on 3 cross-beams
suspended by steel rods retained by nuts.
 The cross-beams were box beams made from C-
channels welded toe-to-toe.
 The original design by Jack D. Gillum and Associates
called for three pairs of rods running from the second
floor all the way to the ceiling.

21. Investigation
 Investigators eventually determined that this
design supported only 60% of the minimum load
required by Kansas City building codes.

22. Investigation
 Havens Steel Company, the contractor responsible
for manufacturing the rods, objected to the
original plan of Jack D. Gillum and Associates,
since it required the whole of the rod below the
fourth floor to be threaded in order to screw on
the nuts to hold the fourth floor walkway in place.
 These thread would probably have been damaged
beyond use as the structure for the fourth floor
was hoisted into position.

23. Investigation
 Havens therefore proposed an alternate plan in
which two separate sets of tie rods would be used:
one connecting the fourth floor walkway to the
ceiling, and the other connecting the second floor
walkway to the fourth floor walkway.
 This design change would prove fatal.
 In the original design, the beams of the fourth
floor walkway had to support only the weight of
the fourth floor walkway itself, with the weight of
the second floor walkway supported completely by
the rods.

24. Investigation
 In the revised design, however, the fourth floor
beams were required to support both the fourth
floor walkway and the second floor walkway
hanging from it.
 With the load on the fourth-floor beams doubled,
Haven’s proposed design could bear only 30% of
the mandated minimum load.

25. Investigation
 The serious flaws of the revised design were
further compounded by the fact that both designs
placed the bolts directly in a welded joint between
two facing C-channels, the weakest structural
point in the box beams.
 Photographs of the wreckage show excessive
deformations of the cross-section.
 In the failure the box beams split at the weld and
the nut supporting them slipped through.

26. Investigation
 Investigators concluded that the basic problem
was a lack of proper communications between Jack
D. Gillum and Associates and Havens Steel.
 In particular, the drawings prepared by Jack D.
Gillum and Associates were only preliminary
sketches but were interpreted by Havens as
finalized drawings.
 Jack D. Gillum and Associates failed to review the
initial design thoroughly, and accepted Haven’s
proposed plan without performing basic
calculations that would have revealed its flaws.

27. AFTERMATH
Aftermath view. The 4th
floor and 2nd floor
walkways were
positioned at the now
boarded entrances. A
parallel 3rd floor walkway
to the left was left intact.

28. Aftermath
 The Missouri Board of Architects, Professional
Engineers, and Land Surveyors convicted the
engineers employed by Jack D. Gillum and
Associates who had signed off on the final
drawings of gross negligence, misconduct, and
unprofessional conduct in the practice of
engineering;
 They all lost their engineering licenses in the states
of Missouri and Texas and their membership to
ASCE.

29. Aftermath
 While Jack D. Gillum and Associates itself was
cleared of criminal negligence, it was stripped of
its license to be an engineering firm.

30. Aftermath
 At least $140 million was awarded to victims and
their families in both judgments and settlements
in subsequent civil lawsuits;
 A large amount of this money came from Crown
Center Corporation, a wholly owned subsidiary of
Hallmark Cards which was the owner of the actual
hotel franchise.
 Life and health insurance companies probably
absorbed even larger uncompensated losses in
policy payouts.

31. Aftermath
 The Hyatt tragedy remains a classic model for the
study of engineering ethics and errors.
 After the disaster, the lobby was reconstructed
with only one crossing on the second floor.
 Unlike the previous walkways, the new bridge is
supported by several columns underneath it rather
than being suspended from the ceiling.

32. Aftermath
 The hotel later reopened, and has been renamed
Hyatt Regency Crown Center.
 It has since been renovated and now serves as one
of the city’s most luxurious hotels.