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What’s left to learn about the Fern Hollow Bridge following the collapse?

Kiley Koscinski
90.5 WESA

On today’s episode of The Confluence: WESA development and transportation reporter Margaret J. Krauss explains how the Fern Hollow Bridge that collapsed was a “K-frame” bridge, one of only six such bridges in the state, and other contextual details about this structure; a CMU professor will use the James Webb Space Telescope to investigate dark matter; and assessing the Penguins as they begin the unofficial second half of the NHL season. 

As questions remain concerning Fern Hollow Bridge collapse, South Busway bridge closed for repairs
(0:00 - 7:30)

A week after the collapse of the Fern Hollow Bridge, Port Authority closed a South Busway bridge in the Mount Washington neighborhood.

“It’s called the Saw Mill Run Boulevard Bridge, sometimes called the Palm Garden Bridge,” says WESA development and transportation reporter Margaret J. Krauss. “An employee saw that there was a joint on the bridge's surface that looked like it had expanded. Immediately, the agency shut the bridge down, had engineers take a look. They said it's stable, but it will be closed indefinitely until they can figure out what caused the shift, and to make repairs.”

The National Transportation Safety Board will be coming out with a preliminary report about the Fern Hollow Bridge collapse. University of Pittsburgh professor of structural engineering Kent Harries told Krauss that “one thing will never cause failure,” and a collapse is usually “a synthesis of multiple issues.”

The Fern Hollow Bridge was first constructed in 1970 and was a “K-frame” bridge, one of only six such bridges in Pennsylvania.

“What that means, typically, is that the part underneath the roadway and then the larger support system are all welded together,” says Krauss. “This one was a non-redundant bridge. So there is no backup support … And so if those pathways aren’t there, the bridge, the stress doesn’t have anywhere to go and the bridge is in danger.”

Non-redundant bridges were more commonly built decades ago, but are now rarer due to updated engineering codes. “Non-redundant bridges are more expensive to build now, they face greater scrutiny, more intense inspections,” says Krauss.

About eight years ago, the Fern Hollow Bridge was posted with a weight limit of 26 tons. Two major Port Authority bus routes, the 61A and 61B, regularly crossed the bridge.

“The articulated, the bendy buses, the 60-footers, weigh 22 tons when they're empty,” says Krauss.

CMU astrophysics professor will use the James Webb Space Telescope to study dark matter
(7:30 - 14:54)

CMU astrophysics professor Matt Walker has spent more than 20 years studying dark matter and will use the James Webb Space Telescope to study the mysterious phenomena. “Dark matter has been confounding astronomers since the 1930s,” says Walker. “I don't know what it is … and I’m not alone, because nobody knows.”

Dark matter cannot be directly observed, but astronomers can infer its existence. Walker explains that astronomers can determine the weight of a galaxy by observing the deflection of light as it travels through a galaxy. “And it turns out when we get our answer [determine the mass of the galaxy], we compare it to the amount of mass that we can see in the form of stars and gas and dust,” says Walker. “And there's always a deficit. The amount of matter that we infer gravitationally is, by and large, ten times larger than the amount of mass we can see.” The difference between these two masses is called dark matter.

Walker says you can think of dark matter as similar to a passing ship. “You can see the wake of a ship, but let's say you're looking too late … You know there must have been something that caused that disturbance in the surface of the water. And so it stands to reason, you can infer that there must have been a ship passing by. So that's loosely an analogy to what we're doing.”

Walker has previously used telescopes in Arizona and Chile to study dark matter, but the James Webb Space Telescope will represent a leap in image clarity. “It’s going to give us the kind of optical power that we have from the ground, but in space,” he says. “And so we expect to have some of the crispest, cleanest, clearest, and most powerful images ever taken.”

He is hoping to use “wide” binary stars to test a prevailing theory about dark matter.

The space telescope launched last Christmas. Walker expects researchers will start making observations in late summer.

After a weeklong break, the Penguins head into the unofficial second half of the season
(14:54 - 21:55)

Following the weeklong NHL All-Star break, the Penguins return to the ice with a face-off against the Boston Bruins tomorrow.

The Penguins entered the break last week after a four-game losing streak.

“They look like a tired team,” says Mike DeFabo, Penguins beat reporter for the Pittsburgh Post-Gazette. “They’re a team that, while they need to clean up some things, I think more than anything, getting a little bit of rest will do them very well.”

Several players have been out due to injuries. Jason Zucker underwent core-muscle surgery last month and Teddy Blueger had surgery for a fractured jaw.

With players going on and off the bench, DeFabo says the Penguins need to focus on their identity as one of the best defensive teams in the NHL.

“They had to stick to that identity, and they had to be the structured, defensive-oriented team in order to have success,” he says. “Getting back to those roots and reestablishing that foundation and specifically managing the puck appropriately, playing well in the neutral zone, and playing well in front of their net. Those are some of the biggest areas of concern for the Penguins in the second part of the season.”

The Confluence, where the news comes together, is 90.5 WESA’s daily news program. Tune in Monday to Thursday at 9 a.m. and 7:30 p.m. to hear newsmakers and innovators take an in-depth look at stories important to the Pittsburgh region. Find more episodes of The Confluence here or wherever you get your podcasts.

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