A Key followup
May 8, 2026 at 8:26 PM by Dr. Drang
Earlier this week, I saw this article in Apple News. It’s from the San Francisco Chronicle and discusses a recent report on the safety of the Golden Gate Bridge. The report is one of several reports spurred by the Francis Scott Key Bridge collapse a couple of years ago.
Image from Wikipedia.
Spoiler: the report finds the Golden Gate Bridge safe—quite unlikely to suffer damage from the impact of a ship. This has to do with the Golden Gate’s two towers:
- The south tower (in the foreground) is surrounded by a reinforced concrete protective structure that a ship would have to strike and destroy before coming in contact with the tower and affecting the bridge’s integrity. We discussed the lack of protective structures around the piers of the Key Bridge.
- The north tower is right up against the Marin County shoreline, where the water is shallow. A large vessel would run aground before striking the tower, scrubbing away most, if not all, of its kinetic energy. A ship that wouldn’t run aground before hitting the tower would be too light to bring it down.
A striking omission from the Chronicle story is a link to the report itself. But that appears to be the fault of Apple News. I can’t read the story on the Chronicle’s website because I’m not a subscriber, but this reprint on Yahoo! News includes the report embedded as a PDF and available to download. So it looks like Apple removed the report itself, which is pretty poor form.
The nice thing about finding the actual report, written by HDR, Inc., is that it confirmed some suspicions I had regarding this paragraph in the Chronicle story:
The resilience of the Golden Gate Bridge partly comes from sheer strength. The south tower, on the San Francisco side, is described in the report as a “robust structural feature like no other” and is surrounded by a reinforced concrete protective shell up to 28 feet thick. It can withstand about 50,000 kips of force, or roughly 25,000 tons. In many cases, engineers found, a ship would crumple and absorb its own impact energy before it could seriously damage the structure.
First, it’s not “sheer strength,” it’s “shear strength.” HDR calculated the strength of the protective structure around the south tower to be at least 50,000 kips when that force is attempting to shear through the reinforced concrete wall. They specifically mention shearing capacity, shearing interfaces, and shearing area when discussing this calculation on pp. 59–60 of the report. While it’s true that engineers tend to be crummy writers, we definitely know the difference between “shear” and “sheer.”
Second, I suspect the writer, Brooke Park, doesn’t know what a kip is. When writing for a general audience1 most people wouldn’t use the word “kip” without saying it’s short for “kilopound.” Which is to say,
There’s no “roughly” about it.2
Still, this oddball paragraph doesn’t affect the overall story and provides the engineers who read it some amusement. Too bad about Apple’s redaction of a link to the report itself, though. That’s sheer incompetence.
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Which HDR isn’t, so I don’t blame them for using structural engineering terms without further explanation. ↩
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You could argue that Park’s “roughly” was meant to parallel the “about” in the previous clause. I think that’s an overly generous interpretation. Also, don’t write to me about long tons or metric tonnes—there’s no way Park was talking about those. ↩