Team 9 Members:

Erin Brobson
Mike Harrison
Andrew Recco
Kate Rosen

Key Words

o Steel Member
o Metal Decking
o Sheeting
o Metal Girder
o Beam-to-Column Connection Construction
o Construction Collapse


On November 3, 1993, a portion of what was to be Chicago's new main post office, collapsed on the corner of Polk and Canal Street (Lou, July 26 1993). During the building's construction, the structure collapsed, killing 2 ironworkers and injuring 5 others. At the time, workers were laying beams in place before fastening them. One of the insecure beams caused the collapse by creating a chain reaction and pulling down between 60 and 70 other steel beams. Supposedly, there was a miscommunication between the engineer and construction workers when the construction design was changed into a more simplified version (Kendall and Talalay, November 4 1993).

Summary of Events

The Chicago Post Office collapse of 1993 was a devastation to the city and its people. Many workers were injured and some even died because of someone’s ignorance for following the required design process. The architect of the project designed the structure of the building as well as the connections; however, the fabricator made the call on how it would be assembled. Instead of following the architect’s beam to column plan of assembly, the fabricator decided on a quicker, simpler route. The original plan was to erect the columns first using thirty, one inch diameter bolts to secure it to the web. Next, using an erection angle the beams would be connected to the columns using two, one inch diameter bolts. Finally connection plates would be welded to secure the beam and column together. With the design changes made by the fabricator, solely for ease of design, the beams were placed one quarter inch further away from the columns then they were supposed to. This change made the use of the one inch diameter bolts impossible. Instead, workers had to switch to using three quarter inch bolts to secure the beam. The change in hardware led to a series of weak connections, some without nuts even holding on the bolts. The connection point where the collapse began, unsurprisingly, was a connection where a nut was not used. After investigation it turned out that many of the other connections were the same. The fabricator was quickly sued and faced many criminal charges. (Field 1997)(Clark 2009)

As Desig​ned
As Built

Causes Of Failure

The source of the failure has been traced to a temporary connection that failed, which in turn led to collapse of as many as 70 additional members that had already been secured. The actual piece that failed was one of the temporary erection angle pieces, which were used to hold the connections together until they would be permanently connected at a later time. The beams that collapsed due to the connection failure were 32 feet long, some weighing as much as four and a half tons. The area that failed was over 4,900 square feet, and there were over a dozen workers on the area at the time of the collapse. Also, the failure took place on an area of construction that had been built up to the third story with steel members and corrugated metal. At over 50 feet above the ground, there was definitely the possibility of more fatalities. Many of the construction workers who were working on the scene had to “ride” the beams to the ground as they were falling all around them. All of this devastation took place based on the failure of one temporary connection member, that was not even to be part of the final construction. (Clark 2009)

Possible Prevention and Learning From the Collapse

This is one failure where the cause of the collapse as been easily identified and the reason for the collapse occurring has been identified as a miscommunication between designer and steel erector during the design process. The most devastating aspect of this collapse is the fact that it was human error, and a lack of solid teamwork and communication that took the lives of two men, and injured others. The collapse could have been easily averted had the design been thoroughly and comprehensively evaluated by all parties after changes to simplify the connections were made during the design process. Had there been a better understanding of what the design changes were, the collapse never would have happened. (Clark 2009)

A very serious error occurred during the building of the Chicago Post Office, and not only can the profession learn from the disaster, but it is a great example for students to examine. Had more consideration been put into the communication of the design to all members involved, the collapse most likely would have never occurred. There was no issue with the temporary erection angle pieces, there was just an issue in how they were utilized at this particular situation and under the given conditions. Several important lessons were learned from the tragic collapse:

Make sure there is clear communication between the engineer, fabricator, and construction workers
§ Construction workers need to follow the specific construction methods and make sure these methods have not changed
§ When laying down beams, secure the bolts with a nut right away
(Nazario 2000)

There remains room for improvement in the construction industry. The Chicago Post Office collapse stood out as an example of why construction work is dangerous. Even now, years after the collapse, the construction industry still has the highest number of fatalities out of all industry sectors (Meyer and Pegula 2004). Though improvements have been made to the equipment used by the construction workers to make them safer, improvements still need to be made to the design phases of many buildings. Equipment, technology, and skills have all been improved, but problems still lie in areas of design and communication. A 1994 study of the UK’s construction industry shows a link between design decisions and safe construction. In fact, 60% of fatal accidents in construction are the result of decisions made before the site work begins. A large portion of construction accidents could have been avoided or reduced with proper design and planning. Ideally, safety should be taken into account during the design phase of a project. Unfortunately, in the US, worker safety is not usually addressed until the construction phase. To better implement accident prevention, designers should receive training on construction safety fundamentals (Hecker 2005).


The man in charge of construction for the post office was fined by the occupational safety and health administration. He was also charged by the US Department of Justice and US Department of Labor. The architect and engineer of the post office were not found liable for the collapse. (Nazario 2000).

Baldacci, Leslie. (November 3, 1993). “Shell of Building Falls – Worker Killed, 6 Hurt.” Chicago Sun-Times. Final Markets Edition. pp 3.
This is a credible source, coming from the Chicago Sun-Times, which is Chicago’s oldest continuously published paper. The article describes the scene of the building collapse. It includes direct quotes from witnesses who experienced the collapse firsthand. This article also suggests the collapse was caused while workers were bolting beams, which had been hung but not yet welded, in place.

Carlos Nazario. (2000). "Chicago U.S. Post Office Collapse." UAB REU Site. <>
This site gives a brief description of the accident on the Chicago post office and what we learned from the collapse.

Carlozo, Lou. (July 26, 1993). “Change of Address – Main Post Office Read For Move Into the Future.” Chicago Tribune. North Sports Final Edition. pp 1.

The Chicago Tribune, one of Chicago’s primary newspapers, published this article in July, months before construction on the site began. This article gives a brief history on Chicago’s post system, spanning from the 1800s to the 1931 Chicago Post Office. It then describes plans for the future post office, to be finished in 1995 as a small, sleek, and efficient office run with the support of an advanced computer system.

Carlozo, Lou and Talalay, Sarah. (November 5, 1993). “Beam Support Eyed in Structure Collapse.” Chicago Tribune.
This article concentrates on the individuals in the accident and the cause of it. After two men had been killed and multiple others were hospitalized, investigation began on the reason of the collapse. Thoughts of human error by the engineer and production error by defective bolts were called into question. Many of the hurt workers have sued and are waiting for the investigators to decide whose fault it was.

Clark, Nanette South. (November 3, 2009). “The 1993 Collapse of Chicago’s New U.S. Post Office.” An Engineer’s Aspect. <>
This article provides details of the events that occurred through newspaper articles. It also explains the consequences of the incident and talks about what went wrong to cause the collapse.

Field, Jacob and Carper, Kenneth. (1997). “Construction Failure”. John Wiley and Sons. New York, NY, 2006.
This resource provides some statistics that relate to the collapse itself as well as the parts that failed.

Hecker, S., Gambatese, J., and Weinstein, M. (September 2005). “Designing for Worker Safety.” Professional Safety. Pp 32-44.
This document explains and proposes ways in which construction safety is being and could be improved.

Kendall, Peter and Talalay, Sarah. (November 4, 1993). “Fell Apart Like An Erector Set.” Chicago Tribune.

This article visualizes the collapse and the panic that it caused the workers. Some made it out; however, others were injured and two even killed. It reports the individual injuries of each of the workers and records reactions of witnesses. The article also references reasons for the collapse; however, so far, the only noticed illegal act was the crane companies misuse of equipment which most likely had no direct effect on the actually collapse.

L., Maureen. (1993). "2 Die in Building Collapse Unwelded Beam Plunges From New Post Office." Chicago Sun-Times. HighBeam Research. <>. February 6, 2010.
This article was written one day after the collapse, so information is still being discovered. There are however, many specific details and it is a good first-hand account of events.

Lehman, Daniel J. (November 5, 1993). “Connectors, Bolts Focus of Probers.” Chicago Sun-Times. Late Sports Final Edition. pp 5.
This article from the Chicago Sun-Times suggests that a sheared seat lug caused the accident. It also describes methods and goals of the officials working on the cleanup site, including precautions will take in dismantling the wreckage. They examine the size, type, and strength of bolts and brackets as well as the workers’ precision in following engineering instructions, the actual engineering design, and other physical evidence.

Lehmann, Danniel J. (November 10, 1993). “Post Office Site Cleanup Set”. Chicago Sun-Times. Late Sports Final Edition. pp 22.
This article is from the credible Chicago Sun-Times newspaper. It was published a week after the collapse, so it includes further information on the incident, as well as plans for the site cleanup. The article uses credible sources, such as Bill Shook, a spokesman for the general contractor, Hyman-Power Construction Co., who confirmed that 20 representatives from the federal government, contractors and unions held two meetings in which they agreed to a plan for the site cleanup.

M. (1996). "Criminal Charges Filed in Post Office Collapse." Chicago Sun-Times. HighBeam Research. <>. February 6, 2010.
This article gives some information about the company in charge of the construction and talks about the charges filed against them.

Meyer, Samuel W., and Pegula, Stephen M. (May 24, 2006). “Injuries, Illnesses, and Fatalities in Construction, 200.” US Bureau of Labor Statistics. <>.
With positions as economists in the Government’s Bureau of Labor Statistics in the Office of Safety, Health, and Working Conditions, both authors have a credible background. The article explains the dangerous conditions of construction work. The article is supported by vast amounts of statistics and facts.

Additional Resources
History Channel. “Engineering Disasters.” A&E Television Networks. New York 2008
This documentary discusses 40 of the worst structural engineering disasters in American History.

Schwab, James. “Planning for Post-Disaster and Reconstruction.” American Planning Association. Chicago, IL 1998