The Kansas City Hyatt Regency Walkway Collapse

“The Worst Structural Disaster In the United States”

BY:Arpit Modh (16BCH035)B.Tech ChemicalNirma University,Ahmedabad.

WHERE: Kansas City, MissouriDATE: July 17, 1981

3rd Floor Walkway Still Intact

• Two Walkways Collapsed

• 114 People Lost Their Life

• Failure of Hanger Rod Connection (4th Floor)

Kansas City HyattJuly 17, 1981

Hotel Features

• The hotel had a grand lobby which featured a multistory atrium crossed by three concrete walkways on the second, third and fourth floors

• The hotel advertised to have many parties and events

Entrance to Hotel and Atrium

Kansas City Hyatt

Entrance

Hyatt General Layout

Background Of Walkway

• July 1980 – Most Modern Hotel in Kansas City finished.

• Consisted of 3 Buildings, 2 were connected by 3 walkways.

Tea-Dance Party Leads to Disaster

• A party was held in the lobby

• Over 2,000 people were in attendance

• People crowded the walkways and the lobby below to watch the dance competition

• The excess weight caused the fourth floor walkway to fall onto the second floor walkway and both walkways collapsed onto the crowded first floor

• The collapse left 114 dead and more than 200 injured

• This was the United States’ most devastating structural failure of the time

Design Problems• Havens proposed the modified design to simplify the assembly task

and to eliminate the need to thread the entire length of the rods

• However, the change in the design doubled the stress put forth on the nut which was under the fourth floor beam and with the change the nut had to support the weight of two walkways instead of just one

• “The ultimate capacity actually available using the original connection detail would have been approximately 60% of that expected of a connection designed in accordance with AISC Specifications” according to the National Building Specifications

On a preliminary design a note was made that the hanging rods needed to have strength of 413MPa but that was left out of the final design and so the fabricator used hanger rods with only 248MPa pf strength.

Walkway’s Original Design

•Box beams as intermediate supports

•One hole at both ends of Flanges

•Threaded single rod

-Hanger for 2nd and 4th floor walkways (3rd floor walkway was separate entity)

Walkway as Constructed

•4th floor box beams:

-Ends had 2 holes

-Outer hole connected to ceiling

-2 lower rods went through inner holes to support second floor walkway

Original Design Modified Design (was used)

The 2nd and 4th floor walkways were

originally supposed to be suspended

from the same rod and held in place by nuts

The fabricator had modified the design to use two hanging rods

and the engineers approved the change without checking it

The hanger rod threads, washer and The hanger rod threads, washer and supporting nutsupporting nutNote: the deformation in the washer caused the beam to Note: the deformation in the washer caused the beam to slip slip

CLOSE-UPS OF SOME OF THE 4TH FLOOR BEAMS

Why Did It Happen?

Combination of :Personnel Errors

A. Design DeficienciesB. Inadequate Oversight &

Review ProcessC. Missed opportunities to

discover errorD. Poor Communication

Factors That Contributed to the Collapse

• Fast Track Process Architectural design changes & conceptual re-designs Drafting Errors Checking errors-Shop Drawings Invalid initial design concept of hanger

Senior engineer personnel changes Phone changes w/o follow-up by detailer or engineer in writing

•Fabricators in-house engineer transferred fabricator’s partial shop dwgs to outside firm who assumed connection was designed•Engineers technician, checked piece size but not connection. (Not Drawn or submitted)•Outside Peer Review didn’t check shop dwg

Factors (Continued)

•“Design Check” questions answers not verified•In-house design check questions following atrium collapse were not verified. No Follow Up •Poor Testing & Inspection

Factors (Continued)

•No Structural Site Representation (Refused several times)

•Engineer Relied (ASSUMED) based on past projects on design of connections by Fabricator, w/no follow-up by Project Manager

Factors (Continued)

Other Factors• Resonating vibrations from dancing and music • Greatly increased stress on box beams.

• Kansas City Building Code required for walkway:• 100lbs/ft2 or 72,000 lbs for each walkway

• Actual load day of tragedy• 9450 lbs (63 people @150lbs each)

• Design Lacked Redundancy

Procedures must be implemented that assure that all Procedures must be implemented that assure that all connections are designed by a competent professionalconnections are designed by a competent professionalPeer reviews and design checks should include a review of Peer reviews and design checks should include a review of shop drawingsshop drawings

Lessons Learned

When questions come up look at surrounding issues for related problemsEOR should be retained to provide full inspection during construction of structureOwner needs on site qualified representation

Lessons Learned

Design and construction is a collaborative Design and construction is a collaborative process that requires professional integrity, process that requires professional integrity, judgment, and integrity on the part of all judgment, and integrity on the part of all participantsparticipantsWe have not yet clearly defined the nature of We have not yet clearly defined the nature of the design and construction process and the the design and construction process and the information flow that is required for success in information flow that is required for success in all respectsall respectsWe have not learned to respect and teach the We have not learned to respect and teach the history of the profession and fully disseminate history of the profession and fully disseminate information of problems that occurinformation of problems that occur

Lessons Not Learned

“It wasn’t a matter of doing something wrong, they just never did it at all. Nobody ever did any calculations…. It got built without anybody figuring out if it would be strong enough.”

• Patrick McLarny, attorney representing state of MO.

In Conclusion

• The two structural engineers lost their Professional Engineering licenses and are no longer able to practice in the states of Missouri and Texas

• Both are now practicing in other states

• A number of firms were bankrupt

• Many expensive legal suits were settled out of court