Letting the Monkeys Go

This post kicks off a new series that breaks open the dark underbelly of structural engineering. Full of facts, figures, & fatal catastrophes (!), you won’t want to miss these posts. So grab your slide rule, red pencil, and lack of social skills and come along!

In one of the famous engineering disasters that they teach you (or at least me) about in school, two hanging walkways collapsed at a Hyatt Regency in Kansas City killing 45 people. The walkways crossed the 4-story lobby of the hotel and hung from the roof by steel rods. They collapsed when the connection between the rods and the beams running under the catwalk fell. Here’s an illustration of that connection:

Catwalk Connection as designed (A) and as built (B)
Illustration by K Ha.

Where the catwalks crossed above and below each other, both were supported on the same rod as shown at left. The beams for the walkway sat on nuts which screwed onto the rod. In order for the nut to do that the rod had to be threaded, which let to the big problem: threaded rod is expensive.

If the same rod was going to be used to support catwalks at different levels, then the whole length of the rod between the two levels would need to be threaded. The contractor asked if they could use two different rods instead and only thread the last few inches of each, at great cost savings. The engineers approved the change without considering the new load flow: the beam and nut experienced twice as much force.

Even so, various safety factors built into the design process should have prevented the collapse if this was the only mistake. It wasn’t; shit broke:


This is a sobering tale for me, because I spend most of my time doing construction administration; changing designs to meet contractor needs. And though I have sort of accepted that earthquakes do things to buildings (and thus people) that we can’t entirely control, to kill people with a mistake…

But at least I don’t have to worry about being tried for murder…or anything else. Or being fined. Or even having to find a new career. The engineers who signed off on the walkway designs, Daniel Duncan and Jack Gillum, lost their engineering licenses in Missouri and Texas, but still practice in other states.

I don’t mean to be unnecessarily punitive, and I realize this may be used against me in the event that I inadvertently kill someone, but that seems pretty light. Sure, the engineers’ and owner’s insurance paid damages, but individuals have to take some responsibility too — and losing one’s state license is nothing, given that your reputation is pretty much shot in that state anyway and contracts are not going to be forthcoming.

A ridiculous example of how white collar crimes aren’t treated seriously in this country. Actresses get more time for shoplifting than an engineer gets for a massacre.  Retributive punishment may be fundamentally problematic, but while we debate that can’t we at least punish people in a rational way?  Is that really too much to ask?

The Rainmakers pretty much sum up my feelings with their Hyatt-inspired “Rockin’ the T-Dance:”

Take a trip with me to Kansas City MO
To the Hyatt House, to the big dance floor
You can still see the ghosts
But you can’t see the sense
Why they let the monkey go
And blamed the monkey wrench

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