Senior Sophister: Structures Project
ACADEMIC YEAR 2006- 2007
THE HYATT REGENCY
WALKWAY COLLAPSE
Group No.3
Group No. 3 :
John Duffin
John Deenihan
Claire O Farrell
Declan Farrell
Lecturer
:
Dr. D. Dwyer
Date
:
25th October, 2006
Hyatt Regency Walkway Collapse
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The Hyatt Regency Walkway Collapse
Introduction:
In July 1980 the most luxurious and modern hotel in Kansas city was
completed and ready for recreational purposes after over four years from
conception to completion. The Hyatt Regency complex consisted of three
connecting structures, a slim reinforced concrete tower on the northern end
containing guests bedrooms and suites, a thirty four meter by forty four meter
(34m x 44m) atrium with a steel and artificial grass roof fifteen meters (15m)
above ground floor level, the southern end of the complex consisted of a four
storey reinforced concrete ‘function block’, containing all essential services.
The northern tower had individual access to the function block via three
pedestrian bridges suspended from the steel trusses of the atrium roof. The
bridge on the second floor (west side of the atrium) was connected to the bridge
on the forth floor by a system of thirty two millimetre (32mm) steel hanger rods
at nine meter (9m) centres. The hanger rods were originally supposed to span
directly from the steel truss roof down through both the fourth and second floor
bridges, suspending them using a single bolt on either side of the box beam (as is
evident in fig.1). Thus the hanger rods suspended from the steel truss would
support the weights of both bridges, while the box beams would support the
loads applied on that individual walkway. On the eastern side of the atrium was
an individual bridge serving the third floor, this was supported in an identical
manner. The main purpose of the bridges was to enable people to pass between
the tower and function block without having to pass through an often busy
atrium.
Bridge Design:
Gillum-Colaco International (GCE) was responsible for the design of all
structural engineering components of the building including the walkways. The
original design (as visible in fig. 1) was to have the walkway supported by two
wide flange beams, one on each side. This was then hung from a box beam. Each
box beam was supported by a washer and nut which was threaded onto the
supporting rod. This type of connection had virtually no moment so the
connection was modelled as a hinge.
Fig. 1: Originally Proposed Box Beam Hanger Detail
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Havens Ltd, were the contractors who were responsible for the fabrication
and erection of the steel truss and supported bridges. Havens manufacturing
department proposed a different connection method (fig. 2). This was a double
hanger rod connection to the box beam; this enabled the contractor to fit each
bridge in position without having to thread the entire hanger rod to fit the washer
and nut. Each support rod of the fourth floor walkway was attached to the
atriums cross beams and suspended by a washer and nut (as shown in fig 2). The
two tie rods were fifty millimetres (50mm) and one hundred and fifty millimetres
(150mm) respectively from the outer edge of the box beam.
Fig. 2: Amended Box Beam Hanger Detail
The amended shop drawings were stamped ‘approved’ by the architects
and ‘reviewed’ by the structural engineers without recalculating the moments and
applied forces of the new connection. The new connection supported the forth
floor bridge via shorter hanger rods between the box beam and the truss roof,
the second floor was now suspended via a shorter tie rod which passed through
the second and fourth floor box beams but was not directly connected to the
hanger rod connected to the steel truss. Thus the forth floor box beams had to
support the load of two walkways rather than the one originally designed for. The
third floor bridge was constructed as originally designed.
Failure:
At 7:05 p.m. on Friday, July 17, 1981, the atrium was filled with over
sixteen hundred people; most were dancing to a tea dance competition when a
sharp thunderbolt sound was heard. Sixty three people had concentrated on the
southern half of the eastern walkway and were dancing to the rhythm of the
music. This vibration caused the fourth floor box beam to split at the welds and
the hanger rods pulled free. As the second floor bridge was suspended by the
forth floor bridge both collapsed and 114 people were killed with over 200
injured. Extensive testing carried out by E.O. Pfrang and R.M. Marshall
determined that the actual dead load of the bridges was 8% higher than originally
calculated but even with the 63 people dancing on the bridge this would not have
caused the collapse.
It was thus evident that the weak element of the structure was the box
beams. Tests carried out on replica samples and some actual undamaged
samples proved that the ultimate strength of the welds and box beams was less
than the applied load (i.e. twice the originally calculated dead load) from the two
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suspended floors. This caused the bolt to first bend the lower flange of the beam
then pull free from the box beam completely. This process started at midspan of
the bridge under the hanger rod and the remaining tie rods were incapable of
supporting the additional loads thus the entire structure collapsed. The
modification made to the walkway was not only under designed but it also lacked
redundancy (i.e. its capability of transferring loads to another structural member
in times of local failure, thus preventing major structural failure).
Fig. 3: Compared Box Beam Hanger Details
Fig. 4: Actual Box Beam After Collapse
Responsibilities:
The National Bureau of Standards analysed the findings E.O. Pfrang and
R.M. Marshall and publish a list of findings, some of which are briefly abbreviated
here:
 The walkways collapsed under substantially less load than was specified by
the Kansas City Building Code.
 The fourth floor box beam connections were the candidates for the
initiation of the walkway collapse.
 All box beam connections both originally designed or actual connections
did not meet with the Kansas City Building Code.
 Neither the quality of workmanship nor quality of material used played a
significant role in initiating the collapse.
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The National Bureau of Standards determined that the originally designed
connections ‘might’ have prevented the collapse, even though they were below
Kansas City Building Code standards.
The Missouri licensing board and the Missouri Court of Appeals found the
fault to be with the structural design engineers because they did not recognise
the essential differences between the original and modified connection drawings.
No recalculation for amended load takedowns was ever produced, thus the
constructed walkway was both uncertified and illegal. The Missouri licensing board
claimed that a huge error had been made on behalf of the structural design
engineers, because no final review of the design would have allowed them to
notice the extra loading on the rods. As a result of these errors all the GCE
engineers who signed off on the walkway design lost their engineering licences in
the states of Texas and Missouri. GCE also lost the right to be an engineering
firm.
Conclusions:
Engineers are responsible for all aspects of a project which involve their
computing and management skills, they have a responsibility to the public and all
individuals involved in the project which is in question for both the construction
and service life of the structure. All aspects of the design must be carefully
designed and calculated to ensure maximum safety and reliability of the works is
achieved. No compromise may be made on safety as it endangers civilians who
are involved at any stage of the works or service life. In the case of The Hyatt
Regency, the associated engineering firm neglected to fulfil their legal duties
when they designed a structure (i.e. the walkways) that was not to compliant
with the Kansas Building Code, but also when they neglected to notice the major
difference in box beam connection proposed. No attempt was made to recalculate
the applied loads of the new connections, thus the structural design firm was
completely liable for the death of 114 people.
References:
http://en.wikipedia.org/wiki/Hyatt_Regency_walkway_collapse
http://ethics.tamu.edu/ethics/hyatt/hyatt1.htm
http://www.answers.com/topic/hyatt-regency-walkway-collapse
Why Buildings Fall Down: How Structures Fail, Matthys Levy, Mario Salvadori,
Publisher: W. W. Norton & Company; Reprint edition (1994), Pages 221-230.
Group 3:
John Deenihan
John Duffin
Claire O Farrell
Declan Farrell
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