Complacency in Engineering

As science and technology progresses and fascinating structures become more common place, humans tend to become complacent. I would like to build on my article previously published on my LinkedIn page [1]A. Gulabi, Complacency and Learning from Mistakes, https://www.linkedin.com/in/abdullahgulabi/detail/recent-activity/posts/ with updates and additional content.

The magnificent dome of the Hagia Sophia in Constantinople located in the historic center of current day Istanbul served as a great challenge to the great mind of engineers and architects until modern times. Hagia Sophia has a main span of around 31 meters. Although damaged several times, the dome built by the nephew of the architect Isidoros the Elder, “Young Isidoros” as entrusted with the work by the Emperor Justinian still stands strong after 1500 years! [2] S. Engül, The Collapse of the Dome of Haghia Sophia, https://istanbulclues.com/hagia-sophia-dome/

As technology made 31 meter clear spans a common achievement, complacency has been rearing its ugly head. The collapse of a pedestrian bridge and the tragic deaths of innocent people

The design of the Bridge. Complaceny in Engineering.
Figure 1: Bridge as designed. [3] Investigation of March 15, 2018 Pedestrian Bridge Collapse at Florida International University, Miami, FL. US Department of Labor, Occupational Health and Safety Administration, Directorate of Construction, July 2019. https://www.osha.gov/doc/engineering/pdf/2019_r_03.pdf

The pedestrian bridge’s main span of ~53 meters (~ 174 ft.) and an adjoining span to make a continuous bridge of 88 meters (~ 289 ft.).

Complacency in Action

Although I would not be repeating the entire incident report here but I would like to highlight the following in the timeline of events leading to 6 fatalities and 10 non-fatal injuries.

Timeline of Events

Timeline of events leading to the collapse of the pedestrian bridge in Florida on March 15, 2018. The author identifies complacency as the root cause.
Timeline of the bridge that collapsed on March 15, 2018 in Miami, FL.

Structural Engineering Basics: Continuity in Structural Members

Civil Engineering and all construction endeavors rely on the basic principle of continuity of materials. Materials transfer loads through a continuous path. The load follows a continuous path until it is transferred from a structural member to another member or surface with sufficient bearing capacity.

It should be noted that cracks in a structural material mean that there is no continuity in that material. It also means that the continuous portion of the material has decreased, meaning less load can follow the path, meaning the overall bearing capacity of the member is decreased.

Armed with this basic knowledge, the following quote from the incident report is quite shocking:

“FIGG hoped that the re-tensioning would either stop further growth of the
cracks, or shrink the crack sizes.”

Shrinkage of crack sizes would only make up for part of the lost capacity at best. This “hope” is one of the shocking revelations of the Accident Report [4]Highway Accident Report, Pedestrian Bridge Collapse over SW 8th Street, Miami, Florida March 15, 2018 https://ntsb.gov/investigations/AccidentReports/Reports/HAR1902.pdf.

Shocking Series of Events

Another shocking fact omitted from the final report are the text message correspondence among the Engineers working on the project.

Screenshot of text by Kevin Hanson to Sam Nunez showing photos of cracks with the message "It cracked like hell".
Screenshot of text by Kevin Hanson to Sam Nunez showing photos of cracks with the message “It cracked like hell”.

I will refrain from reproducing the entire content of the reports provided in the references but I would like to note that the investigation report identifies Kevin Hanson as one of the most experienced Post Tensioning personnel in Florida. Despite the warnings, concerns regarding the safety and the structural integrity of the bridge were not addressed.

Conclusion: Complacency from Everyone

The probable causes are given in the Highway Accident Report[4] is quoted below.

3.2 Probable Cause

The National Transportation Safety Board (NTSB) determines that the probable cause of the Florida International University (FIU) pedestrian bridge collapse was the load and capacity calculation errors made by FIGG Bridge Engineers, Inc., (FIGG) in its design of the main span truss member 11/12 nodal region and connection to the bridge deck. Contributing to the collapse was the inadequate peer review performed by Louis Berger, which failed to detect the calculation errors in the bridge design. Further contributing to the collapse was the failure of the FIGG engineer of record to identify the significance of the structural cracking observed in this node before the collapse and to obtain an independent peer review of the remedial plan to address the cracking. Contributing to the severity of the collapse outcome was the failure of MCM; FIGG; Bolton, Perez and Associates Consulting Engineers; FIU; and the Florida Department of Transportation to cease bridge work when the structure cracking reached unacceptable levels and to take appropriate action to close SW 8th Street as necessary to protect public safety.

As seen above, everyone involved ultimately contributed to the failure of the structure, the collapse of the bridge and ultimately the death and injury of 16 people.

Who am I?

I am a Civil Engineer with a Masters degree in Construction Engineering and Management from Boğaziçi University and an MBA degree. Visit my personal homepage for more information about me.

References

References
1 A. Gulabi, Complacency and Learning from Mistakes, https://www.linkedin.com/in/abdullahgulabi/detail/recent-activity/posts/
2 S. Engül, The Collapse of the Dome of Haghia Sophia, https://istanbulclues.com/hagia-sophia-dome/
3 Investigation of March 15, 2018 Pedestrian Bridge Collapse at Florida International University, Miami, FL. US Department of Labor, Occupational Health and Safety Administration, Directorate of Construction, July 2019. https://www.osha.gov/doc/engineering/pdf/2019_r_03.pdf
4 Highway Accident Report, Pedestrian Bridge Collapse over SW 8th Street, Miami, Florida March 15, 2018 https://ntsb.gov/investigations/AccidentReports/Reports/HAR1902.pdf

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