The Fern Hollow bridge was rated ‘poor’ when it collapsed in January. Dozens of other bridges across Allegheny County share the same or worse rating.
Still, don’t panic, says longtime structural engineer Kent Harries to Pittsburgh travelers. With more news about increasing dangers for pedestrians, Harries suggested collapsing bridges aren’t our biggest threat.
We spoke with Kent Harries, an engineering consultant and professor of structural engineering at the University of Pittsburgh, known to some as “the bridge guy,” about his perspective on what we can learn from the collapse, why the public shouldn’t panic and ideas for safer travel.
The interview has been edited for brevity and clarity.
You’ve said before: “We can’t possibly prevent all bridge failures. … The important thing is we learn from that going forward, and I have no doubt we will learn from this, too.” What do you think we can learn from the Fern Hollow collapse?
The takeaway from these kinds of failures is that we are neglecting maintenance. And when I say we, I’m talking we as a nation and going beyond the nation as well. And that’s a big issue. We’ve got a structure that was, what, not quite 50 years old or barely 50 years old. At the time, it would have been designed with a 75-year life in mind. But all you have to do is look around Pittsburgh to see that bridges need to last a lot longer than that. And it was in a very poor state of repair. Now, there’s all sorts of reasons for that.
Do you think the infrastructure bill will be adequate to address the ongoing deterioration of bridges? What is the ratio of support we’re getting from the infrastructure bill to the support we need?
That’s a good question. And I think you could probably ask 15 economists and get 25 different answers to that question. The infrastructure bill is good in the sense that at least it’s something, right? We’re pointing in the right direction. There is some recognition. Now keep in mind what was passed was half of what was asked initially. …
All the numbers that we talk about are to sort of bring infrastructure back up to a serviceable standard. That doesn’t address the need for new infrastructure. So let’s look at Pittsburgh for a second. You know, Pittsburgh’s an aging city. The population is half of what it was in the ’40s and ’50s. But let’s look into the future for a minute. At some point, whether it’s 20 years down the line or 50, Florida is going to be underwater. California will have burnt out. Half of the coast is dealing with five hurricanes a year. Pittsburgh’s going to be a location in North America that’s not a bad place to move to.
But what will that mean, you know? It’ll place larger demands. It will mean that not only do we need to maintain what we have, but we need to build new.
We will [eventually need to make] decisions that we are going to have to shut down bridges and not replace them because the resources just simply are not there. Now, that’s going to be a political decision, let’s face it. Right? Let’s not pretend. And it will probably bring up other issues like social justice issues. If you’ve got two equivalent bridges that essentially carry the same traffic and carry two different communities, which one is likely to be shut down and replaced? Hopefully, we’re only shutting down those bridges that carry a couple hundred cars a day. But for those couple of hundred people, that’s important.
And looking at Pittsburgh, if you look at the amount of money that it would take to bring our bridge infrastructure up to speed, that’s probably less money than we need to bring the sewer system up to repair. (ALCOSAN’s effort to eliminate combined sewer overflows is expected to cost $2 billion.)
What would you say to a Pittsburgh traveler — car, foot or bike — who might now be anxious about crossing Pittsburgh bridges? There are bridges rated worse than Fern Hollow, but you’ve said before that the public “shouldn’t panic.” Why not?
I don’t want to belittle the anxiety … by any stretch of the imagination. But, it’s not something to be concerned with. I would be much more anxious jaywalking middle-block in Oakland. Hell, I’d be more anxious walking in a crosswalk in Oakland than I would be going across a bridge. Not to belittle it, but there’s not a real risk. I’ll leave my building and try to cross the street and that’s much more dangerous. I’m a cyclist and riding in the bike lanes is much more dangerous.
We know that Fern Hollow and other bridges that have failed are usually deteriorating and corroding in lots of different ways. You’ve said before that bridge collapse is usually a “synthesis of multiple issues.” Are there telltale signs or things travelers can look out for to know if a bridge is safe to cross or nearing failure? Are there things you can actually see or look out for?
The driver should not be doing that, they should be focused on the road. Passengers can look around. But the answer is no. If you see a great big ledge in front of you , then there is no bridge. But apart from that, no.
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