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Bridges: Nature Abhors Them · Stuff You Should Know

0:01
Speaker 1: Welcome to you Stuff you Should Know from House Stuff
0:04
Speaker 1: Works dot com. Hey, and welcome to the podcast. I'm
0:12
Speaker 1: Josh Clark with Charles W. Chuck Bryant with Jerry Rowland
0:16
Speaker 1: with me Josh Clark, Mr. Stuff you Should Know featuring
0:19
Speaker 1: Josh Clark's about to say you never introduced yourself and
0:22
Speaker 1: then you done did it twice three three times? Oh yeah,
0:27
Speaker 1: you always introduce your but you never say your last name.
0:30
Speaker 1: I think that's extruct me. John. No, I say I'm
0:34
Speaker 1: Josh Clark, do you Yeah? Every time I should listen
0:37
Speaker 1: to the Sometimes that explains the glazed overlook in your
0:41
Speaker 1: eyes whenever we start um bridges. Yeah, is that your intro? Ye?
0:50
Speaker 1: I like them. Maybe we can add like a scat
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Speaker 1: drummer on top of that. We have that kind of
0:56
Speaker 1: um when we're doing uh listener mail, there's a little
0:59
Speaker 1: bit of oh yeah, well that's not scat drumming. I
1:02
Speaker 1: would say that's more of a shuffle mhm scots like
1:07
Speaker 1: yeah like that. Yeah, you should get Hodgment to scat
1:10
Speaker 1: for you sometime. He's got a lot of boot boot
1:14
Speaker 1: bidus going on when he's scatting any jazz hands. No, No,
1:20
Speaker 1: it's not exactly Manhattan Transfer level. He's intermediate. Yeah uh
1:28
Speaker 1: yeah so again, Princess. Yeah, you know, I bet we're
1:32
Speaker 1: gonna hear from some folks because there are bridge enthusiasts,
1:36
Speaker 1: which I think is kind of neat. Yeah. Well, I
1:38
Speaker 1: mean they're like modern marvels of engineering, and actually there's
1:42
Speaker 1: some ancient marvels of engineering too, as far as they are.
1:47
Speaker 1: Um yeah, there you Basically I was talking to our
1:52
Speaker 1: pal um Adam the architect o, the bridge builder. No, yeah, uh,
1:58
Speaker 1: he's a building builder. We're a building designer. I don't
2:02
Speaker 1: know if he actually knows how to build the buildings.
2:04
Speaker 1: He just knows how to tell other people how to
2:06
Speaker 1: build that. Adam can't swing a hammer. He was saying that,
2:10
Speaker 1: um uh the um. Basically, the structural engineers who designed
2:17
Speaker 1: bridges are just straight up geniuses. Like it requires a
2:21
Speaker 1: basically a genius to factor in all of this stuff. Yeah,
2:25
Speaker 1: anyone can design a building, you know, there's just four
2:28
Speaker 1: walls and a bunch of floors. Put a roof on it.
2:31
Speaker 1: Bridge though it's different. Yes, right, there aren't walls really, Um,
2:37
Speaker 1: there can be bridges of Madison County they had walls.
2:39
Speaker 1: Oh yeah, they have walls. I was going to mention
2:41
Speaker 1: the bridges of Madison County. Yeah, I love those that
2:44
Speaker 1: that'd be a beam bridge, I guess, yeah, with a trust, right,
2:50
Speaker 1: the top trust was the top trust film a through
2:54
Speaker 1: trust through trusts, and then below that. If they were
2:58
Speaker 1: below it would be a deck trust. But don't know
3:00
Speaker 1: if that counts as a trust. It's more just like
3:01
Speaker 1: a house on top of the bridge. I bet their
3:04
Speaker 1: structural support there. May thought it was mainly just to
3:07
Speaker 1: keep the rain off of you when you crossed the bridge,
3:09
Speaker 1: like just an extra little thank you for crossing the bridge.
3:12
Speaker 1: I thought it was just to draw in Lackey tourists
3:15
Speaker 1: who wanted to have their picture made. Another famous bridge,
3:20
Speaker 1: the one that the Headless Horseman couldn't cross in the
3:23
Speaker 1: legend of Sleepy Hallow. Oh yeah, wouldn't that a bridge? Sure?
3:27
Speaker 1: Trolls of under bridges that draw bridges are pretty cool.
3:31
Speaker 1: Have you ever seen Maximum Overdrive? The beginning of that movie? Um,
3:35
Speaker 1: it's been many, many years. I saw it again. I
3:38
Speaker 1: saw it again very recently, like this year, and it
3:40
Speaker 1: is it's maybe better than it was before. It holds
3:43
Speaker 1: up as a crappy movie. Still. Yeah, the whole soundtrack
3:47
Speaker 1: is a C D C by the way, which you
3:49
Speaker 1: should love the whole sound I do love that, and
3:52
Speaker 1: I do remember that. And didn't Stephen King direct that,
3:56
Speaker 1: which he doesn't do much, right, No, but maybe it's
3:58
Speaker 1: the only one is definitely far interesting. But there's a
4:01
Speaker 1: great draw draw bridge scene in there. Uh did someone
4:06
Speaker 1: jump it jump the span as it raised? No? I
4:11
Speaker 1: think their car fell into their truck felling. Okay, because
4:14
Speaker 1: usually the drawbridge scene is like I can make it.
4:18
Speaker 1: Uh No, this one was you're all doomed and uh,
4:24
Speaker 1: let me also recommend Budapest for bridges. You mean I
4:27
Speaker 1: went to Budapest a couple of New years as ago. Yeah,
4:30
Speaker 1: I went there like twenty years ago. Okay, so yeah,
4:33
Speaker 1: you know the bridges are amazing that I think like
4:35
Speaker 1: five because they connect the two sides, yeah, Buddha and Pest, right,
4:41
Speaker 1: and each one is totally different, like it's just a
4:43
Speaker 1: completely different design. Yeah, and they're just all gorgeous. Yeah,
4:48
Speaker 1: let's just start with a bunch of bridge recommendations. I'm
4:51
Speaker 1: going to recommend the City of Pittsburgh baseball game there,
4:56
Speaker 1: and it's just just gorgeous. Those beautiful bridges that you
4:59
Speaker 1: can see from the baseball stadium and the river. That
5:02
Speaker 1: was when we were a Toyota commercial ring. Right. Yeah,
5:07
Speaker 1: I stayed in the hotel and just eight um sog
5:11
Speaker 1: copenny r no chicken sog. Right, it's just like a
5:14
Speaker 1: quarter of it. But you can see the baseball stadium
5:17
Speaker 1: out your hotel window. Yeah. And I saw some bridges
5:20
Speaker 1: to Yeah, you walk across the bridge to get there.
5:22
Speaker 1: Really swe did what else any other bridges, well, Brooklyn Bridge,
5:28
Speaker 1: Golden Gate Bridge, this are like the famous ones. They're
5:31
Speaker 1: barely even worth mentioning. Yeah, but the Brooklyn Bridge is
5:35
Speaker 1: for your money. It's which is free. It's a pretty
5:38
Speaker 1: great thing to do to walk across it. It's it's
5:41
Speaker 1: just beautiful. I've never done that. You should do it.
5:44
Speaker 1: Even the Geico Lizard did it, and I haven't. That
5:47
Speaker 1: guy's like Australian or something. Well, maybe we should just
5:49
Speaker 1: animate you and have you walk across it. Uh. One
5:52
Speaker 1: more thing if you want to know more about the
5:55
Speaker 1: Brooklyn Bridge, I don't remember which one we talked about it,
5:58
Speaker 1: and but there is a really cool documentary about the
6:01
Speaker 1: Brooklyn Bridge and it's building by Ken Burns. Oh wow,
6:06
Speaker 1: I believe it's on Netflix. I'll have to check that
6:08
Speaker 1: out then, yep, because I like cain Burns and Brooklyn bridges,
6:14
Speaker 1: all right, you ready? Uh yeah, man, So bridges have
6:19
Speaker 1: been around for a very long time. This article is
6:22
Speaker 1: by Robert Lam and another dude named Michael Morrissey together.
6:26
Speaker 1: I believe they were locked away in a closet for
6:29
Speaker 1: like a couple of months while they worked this out together. Well,
6:33
Speaker 1: he the one of the first ones that talking about
6:35
Speaker 1: ancient bridges that they mentioned in here, the Arcadeco Bridge
6:40
Speaker 1: in ancient Greece. Did you see that thing? It's really neat.
6:44
Speaker 1: I mean it still stands. It's a three thousand year
6:47
Speaker 1: old bridge, and uh, it's just kind of cool to
6:50
Speaker 1: think about, you know, ancient civilizations and ancient times. People said,
6:55
Speaker 1: well I want to get over there, and I'm here,
6:59
Speaker 1: and so let's build something to do that. I need
7:02
Speaker 1: something to walk on or drive my card over that.
7:05
Speaker 1: Si Um, I just saw that. I saw the world's
7:09
Speaker 1: oldest bridge that's still in use. Um is in Turkey
7:13
Speaker 1: over the Mulis River, I believe from eight Do you
7:20
Speaker 1: know what that's how it's constructed. It is a single
7:23
Speaker 1: It is a single stone slab. Archy. No, it is
7:28
Speaker 1: a stone slab, single arch. Yeah that makes sense. Yeah,
7:33
Speaker 1: very basic. Yeah, but the arch it's super old. But
7:39
Speaker 1: it's still in use today because whoever figured it out
7:44
Speaker 1: came upon this very elegant solution to a lot of
7:46
Speaker 1: problems that a bridge poses. Because, as you were saying,
7:50
Speaker 1: when when you come upon like a river or creek
7:52
Speaker 1: or something, you say, I'm on this side and I
7:54
Speaker 1: need to be on the other side, so I need
7:55
Speaker 1: something to walk across. Yeah, okay, that's a basic solution.
7:59
Speaker 1: But the further and further you get, the more and
8:02
Speaker 1: more problems. Like, as bridge builders say, most span more problems. Yeah,
8:08
Speaker 1: I guess what we should have said is I want
8:09
Speaker 1: to walk across and live. I want to walk all
8:13
Speaker 1: the way across, right, I don't want to fall down. No,
8:16
Speaker 1: I don't want to get halfway across and have it snapped.
8:18
Speaker 1: So over the years, as people have come upon problems
8:24
Speaker 1: where you are going to build a bridge that will
8:27
Speaker 1: snapping and kill you, they've come up with solutions to
8:30
Speaker 1: prevent that from happening. That's pretty much the pursuit of
8:33
Speaker 1: bridge building is coming up with ways to prevent a
8:36
Speaker 1: bridge from collapsing, and a lot of trial and error
8:39
Speaker 1: over the years, you know, and a lot of real
8:42
Speaker 1: significant disasters. In fact, there's a Time magazine slide show
8:47
Speaker 1: um called worst Bridge Collapses in Past one years, um,
8:51
Speaker 1: and it's got all these photos of collapse bridges and
8:53
Speaker 1: little descriptions and the number of fatalities and everything. But um,
8:57
Speaker 1: it's it's really interesting all these different bridges of lapsed
9:00
Speaker 1: and failed for all these different reasons. Well and after
9:03
Speaker 1: each one, uh, it's very sad, of course, but after
9:06
Speaker 1: each one someone goes, oh, well we should do this
9:09
Speaker 1: for the next one. We should not forget that bolt
9:13
Speaker 1: next time. Well, that's that could be human Ara, True,
9:15
Speaker 1: that's happened. Yeah, I'm sure. All right. So should we
9:20
Speaker 1: start off with the bats be A t s. Beams, arches, trusses,
9:26
Speaker 1: and suspensions are the main components of the structural components
9:31
Speaker 1: of a bridge. It's very simple, that's it. That's all
9:35
Speaker 1: you need to know to construct your own bridge. And
9:38
Speaker 1: with these four things you can make almost any kind
9:41
Speaker 1: of bridge. Um. We're gonna cover mainly beam bridges, arch bridges,
9:46
Speaker 1: trust bridges, suspension bridges, and then the super cool looking
9:51
Speaker 1: cable stayed bridge. It is super cool, probably my favorite
9:55
Speaker 1: looking bridge in the world that I came across and
9:58
Speaker 1: reach researching. This is a cable stayed bridge, the one
10:01
Speaker 1: that's in the article. Oh yeah, they look like look
10:05
Speaker 1: like sales gorgeous, the big triangles rising up. It's lovely.
10:09
Speaker 1: But they look a little more modern to me. They
10:11
Speaker 1: don't have that classic architecture like the Brooklyn Bridge does,
10:16
Speaker 1: or like the Tower Bridge in London. Yeah. I think
10:18
Speaker 1: that's why I like it. Yeah, you like the modern look. Yeah, yeah,
10:21
Speaker 1: you're a modern guy. I'm super mod alright. Um. They
10:26
Speaker 1: point out in the article, which is very key. What
10:28
Speaker 1: you talked about. The span of the bridge is the
10:31
Speaker 1: distance between the supports, and that's where um, that's where
10:35
Speaker 1: it all goes down. Basically, Yes, that's got to be strong,
10:38
Speaker 1: there be those are something that every single bridge has
10:41
Speaker 1: is a span and at least one support most likely
10:44
Speaker 1: to Yeah you know, um, and there's different The reason
10:51
Speaker 1: that there are different types of bridges because different bridge
10:55
Speaker 1: designs that that bats designs what is it, beams, arches, trusses,
11:00
Speaker 1: and suspension. They provide stability for varying span lengths. So
11:06
Speaker 1: like a beam, if you have like a fifty ft
11:09
Speaker 1: um span, just put a a like a very long
11:13
Speaker 1: log over over the span and there you go, there's
11:16
Speaker 1: your bridge. But as you get further and further along,
11:19
Speaker 1: you have more and more problems supporting that span, so
11:22
Speaker 1: you need different types of solutions, and the different length
11:26
Speaker 1: of the span calls usually for a specific type of
11:29
Speaker 1: bridge design. Yeah, and generally it it'll I mean there's
11:32
Speaker 1: a lot of overlap, of course, but UM beam bridges
11:35
Speaker 1: tend to be the shortest, followed by arch bridges and
11:37
Speaker 1: then suspension bridges, and I think those UM the cable
11:42
Speaker 1: stayed bridge is is kind of a suspension bridge, so
11:45
Speaker 1: that counts. It's like a kind of a variation that
11:48
Speaker 1: can be very long as well. Yeah, not quite as
11:51
Speaker 1: long as suspension bridges though from what I understand, and
11:54
Speaker 1: this UM, the suspension bridge affords the longest span. Okay,
11:58
Speaker 1: so you've got a big long span, it's it's suspension time. Yeah.
12:02
Speaker 1: And they're also super expensive. Yeah, suspension bridges because all
12:06
Speaker 1: the bridge builders know that you've got a log span
12:09
Speaker 1: that you're trying to cross, you probably got some deep
12:10
Speaker 1: pockets and they're gonna milk you for it. Oh yeah,
12:12
Speaker 1: every penny. Yeah. Yeah, Like you need a suspension bridge
12:16
Speaker 1: I'm your guy. Um, all right, so let's talk about
12:20
Speaker 1: there are a lot of different forces that can act
12:23
Speaker 1: on a bridge to make it not as stable. Um.
12:26
Speaker 1: Will cover a few of the other ones later, but
12:30
Speaker 1: the main two here early on our tension and compression.
12:35
Speaker 1: And the very easy way to think about these two
12:37
Speaker 1: things is tension is like if you if you and
12:40
Speaker 1: I are pulling a rope, like you're on one end
12:42
Speaker 1: and I'm on the other, We're gonna pull that sucker tight,
12:45
Speaker 1: and uh, I'm gonna fall over due to your massive strength.
12:49
Speaker 1: I'm pretty huge, but um, there will be some tension
12:52
Speaker 1: in that rope. Yeah, f do you fall down? Yeah?
12:57
Speaker 1: And I'd start laughing if there would be tension. Sure.
13:00
Speaker 1: The tension is the lengthening of something. Compression is the
13:03
Speaker 1: shortening of something, Yeah, like a spring collapse. Right. So
13:06
Speaker 1: it's easy to visualize when you're talking like springs and
13:08
Speaker 1: ropes and that kind of thing. But if you're talking
13:10
Speaker 1: about just a single deck of a bridge, which you
13:13
Speaker 1: think of as one piece, Um, it's tough to it
13:17
Speaker 1: starts to get tough to visualize it until you realize
13:21
Speaker 1: that you have to look at like a bridge deck
13:23
Speaker 1: like the roadway on the bridge as really having a
13:27
Speaker 1: top and a bottom. Yes, and forces, Well, the compression
13:31
Speaker 1: acts in the downward motion on the top, and the
13:34
Speaker 1: tension acts from the underneath coming up on the bottom. Right,
13:38
Speaker 1: So the bottom of the bridge, underneath it, of the
13:42
Speaker 1: deck is going to be spread out under the force
13:46
Speaker 1: of tension. We're on top where it's being pushed down compressed.
13:51
Speaker 1: That's compression. Yeah, and they kind of in a weird way,
13:55
Speaker 1: work together. Even though they're sort of opposite things, they're
13:58
Speaker 1: definitely related, right. Uh. And what will happen is if
14:02
Speaker 1: these uh, if you aren't a very good bridge builder, um,
14:07
Speaker 1: buckling will occur when it's compressed on the top, and
14:11
Speaker 1: snapping can occur on the bottom when tension is at work.
14:16
Speaker 1: That's right. It all sounds very confusing, but if you
14:19
Speaker 1: just I gotta do is like put your hand out
14:21
Speaker 1: and look at it, you know, and so or if
14:24
Speaker 1: you take and push down on your hand or on
14:27
Speaker 1: your hand, right, you know what I'm saying, like that, yeah,
14:31
Speaker 1: like that. Um, the whole thing becomes very very evident
14:35
Speaker 1: when you look at a beam bridge, right, the most
14:39
Speaker 1: basic form of a bridge, like if you dropped a
14:41
Speaker 1: log over a river, right, and this this thing. Um.
14:44
Speaker 1: This article used the example of like taking a pair
14:47
Speaker 1: of milk crates and putting like a two by four
14:50
Speaker 1: across them. Right, if you put like a bowling ball
14:54
Speaker 1: on a bowling ball stand so it doesn't roll around, Yeah,
14:57
Speaker 1: that'd awkward on top of them, on top, right in
15:00
Speaker 1: the middle of your two by four, which makes up
15:03
Speaker 1: your beam bridge deck. Right, Um, you're gonna see that
15:08
Speaker 1: it bows, and what you're seeing is that on the
15:10
Speaker 1: top it's being compressed. On the bottom, it's being um tensed, right. Um.
15:16
Speaker 1: And what you've just done is add a load to
15:19
Speaker 1: that bridge. And there's two kinds of loads to start
15:21
Speaker 1: out with. There's a deadload, which is the weight of
15:24
Speaker 1: the bridge and all of its materials combined. And then
15:27
Speaker 1: there's a live load, which is say, like the cars
15:30
Speaker 1: and the people and the trains and everything that that
15:33
Speaker 1: add the extra weight while they're moving across it and everything.
15:36
Speaker 1: And as you add this extra load, first of all,
15:38
Speaker 1: the bridge is already dealing with its deadload. You's got
15:41
Speaker 1: to hold that up. That's job number one for a bridge. Yeah,
15:44
Speaker 1: Like if you had a three hundred foot two by
15:46
Speaker 1: four and two milk crates it's gonna sag in the
15:49
Speaker 1: middle just naturally, right, and it might even break. And
15:51
Speaker 1: there have been bridges that have been built that where
15:54
Speaker 1: the guy forgot to carry the one or whatever and
15:57
Speaker 1: they couldn't stand up under their own weight and they
15:59
Speaker 1: collapse from their own weight. They collapse from the deadload.
16:02
Speaker 1: So job number one of the bridge is to support
16:04
Speaker 1: its own weight. Job number one point one is to
16:09
Speaker 1: support all of the liveload the traffic that goes across
16:13
Speaker 1: it as well. That's right. Uh. And the two ways
16:16
Speaker 1: that you're going to do this to counteract tension and
16:18
Speaker 1: compression are dissipation and transference force or transferring the force.
16:24
Speaker 1: So with dissipation you spread out that force equally, you
16:28
Speaker 1: spread out over a wide area, and with transferring um
16:32
Speaker 1: you move the area of weakness to an area of strength, right,
16:36
Speaker 1: which pretty simple. Yeah, they're kind of tough to distinguish sometimes, Yeah,
16:40
Speaker 1: you know what I mean. But for example, like the
16:42
Speaker 1: best example of dissipation is the arch, which we'll talk
16:46
Speaker 1: about how that works in a second. Um. But suspension
16:50
Speaker 1: bridges are best at transferring the um the tension and
16:56
Speaker 1: compression forces. That's right. So if you're if you're talking
16:59
Speaker 1: about to beam bridge that most basic kind. Uh. The
17:02
Speaker 1: other thing they're gonna do to make it stronger, of course,
17:04
Speaker 1: is use back in the old days, use wood than
17:06
Speaker 1: later iron and then steel, maybe some concrete mixed in um.
17:12
Speaker 1: But the size of the beam is gonna be really important.
17:15
Speaker 1: Like the height of the beam is important because the
17:18
Speaker 1: the top is gonna experience stress, the bottom is gonna
17:20
Speaker 1: experience stress in the middle not as much. So a
17:23
Speaker 1: good I beam, a good tall ibam is what you want. Yeah,
17:27
Speaker 1: and I didn't realize that. That's why I beams are made.
17:29
Speaker 1: Like I beam, the center of the deck or the
17:34
Speaker 1: beam or whatever, any kind of beam is going to
17:37
Speaker 1: experience the least amount of compression or tension. It's really
17:40
Speaker 1: the top or the bottom. So you don't have to
17:43
Speaker 1: put quite as much material into the center of the
17:45
Speaker 1: beam as you do the top and the bottom to
17:48
Speaker 1: prevent buckling and snapping. That's right. So with the beam bridge,
17:51
Speaker 1: you're gonna add what's called a truss uh to make
17:54
Speaker 1: it stronger. This uh, we'll talk about trust is more
17:57
Speaker 1: but it's basically reriangulated strength. And you'll see a trust
18:02
Speaker 1: if you've ever seen like a a train bridge like
18:07
Speaker 1: you see a trust on top or like in areas
18:11
Speaker 1: where they get a lot of snow, roof supports will
18:14
Speaker 1: frequently be trusses. Yeah, and that's a three trust on
18:17
Speaker 1: top we already said. And if it's underneath then it
18:20
Speaker 1: is uh the deck trust and you can have both,
18:24
Speaker 1: but usually, like with the railroads, you'll see like that
18:27
Speaker 1: top trust not the same as a trestle. That's different.
18:31
Speaker 1: That's like like a roller coaster, you know. So after
18:36
Speaker 1: this break, why don't we talk more about trust bridges? Nice? So,
19:00
Speaker 1: no joke. Trusses are one of my favorite things now,
19:03
Speaker 1: it's pretty neat. After doing some research into him, I'm like,
19:06
Speaker 1: I love trust. Yeah, and it's because they're so elegant
19:13
Speaker 1: and simple. They're elegantly simple basically. So, um, I saw
19:17
Speaker 1: this really great explanation where it was on Make magazine
19:22
Speaker 1: and I think it was called like ask Make, how
19:25
Speaker 1: do trust? His work? Pretty straightforward, um, and it basically
19:29
Speaker 1: had like a really get a great graphic of taking
19:34
Speaker 1: using popsicle sticks. Right, Let's say you make a square
19:37
Speaker 1: out of popsicle sticks, and you joined the popsicle sticks
19:41
Speaker 1: together at the corners where the ends all meet. Ye,
19:43
Speaker 1: little Elmer's paste. Maybe makes sense. It seems pretty supportive, right,
19:48
Speaker 1: But when you pressed down on any one of those joints,
19:51
Speaker 1: which is where the load's going to be centered or
19:54
Speaker 1: distributed most remember the ends the square shift to the side,
20:00
Speaker 1: and all of a sudden you have a rhombus. Well,
20:02
Speaker 1: rambus is inherently less structurally sound than square, which is
20:06
Speaker 1: why you very rarely see rambus as in architecture. Right,
20:11
Speaker 1: with a triangle, when you press down at any one
20:13
Speaker 1: of the joints, it distributes that compression or tension directly
20:19
Speaker 1: through the center of the beam, so the triangle stays
20:24
Speaker 1: totally rigid. And when you add, the more triangles you add,
20:27
Speaker 1: the more support you have, So they're like basically like
20:31
Speaker 1: as far as the shape goes, the superconductor of transferring
20:34
Speaker 1: or distributing compression or tension. Yeah, that's a good way
20:39
Speaker 1: to put it. And that's why when you see that
20:41
Speaker 1: that train tress alone that has that trust on topics,
20:44
Speaker 1: got all those beautiful diagonal uh pieces of metal. And
20:49
Speaker 1: it's not just for for looks, even though it is
20:51
Speaker 1: cool looking. No. One of the other great things about
20:54
Speaker 1: a trust is that there you know, it's like just
20:57
Speaker 1: a three steel beams or three whatever aluminium beams. They're
21:01
Speaker 1: just three pieces of metal usually fixed together. And that's
21:05
Speaker 1: that's the other key that I left out. They have
21:08
Speaker 1: to be connected at the ends equally distributed from each end. Right, So,
21:14
Speaker 1: let's say you you drill a hole to to rivet
21:16
Speaker 1: one side of the trust to another, or one end
21:19
Speaker 1: of the trust to another end, the the other end
21:23
Speaker 1: has to be equally far away. Do you see what
21:26
Speaker 1: I'm saying. Yeah, yeah, okay, they wouldn't just be like
21:28
Speaker 1: just drill that other one wherever. So anyway you have
21:31
Speaker 1: to the place where the trust sides join together has
21:35
Speaker 1: to be on the ends. And then but one of
21:38
Speaker 1: the things that it allows for is for wind to
21:40
Speaker 1: blow through it easily. That's a huge point about trusses.
21:45
Speaker 1: They're not solid in that they don't they don't put
21:50
Speaker 1: up a lot of resistance to when they allow it
21:52
Speaker 1: to flow through, which is really kind of what you want.
21:54
Speaker 1: We'll see when you're building bridges. Yeah, I think even
21:57
Speaker 1: the covered bridges have is more of a that's type
22:00
Speaker 1: thing on the sides. Right. Yes, it's not solid, is it.
22:04
Speaker 1: That'd be dumb a covered bridge. Yeah. I thought the
22:08
Speaker 1: walls were usually like a lattice so wind could pass through.
22:10
Speaker 1: Now and they had a than a roof and like
22:14
Speaker 1: a lattice e side is there, right, Yeah, maybe there's
22:17
Speaker 1: all kinds. I think those are just to keep the
22:21
Speaker 1: rain off. Oh yeah, that's what you said earlier and
22:25
Speaker 1: keep shooting down there. Yeah. But anyway, trust is rock,
22:31
Speaker 1: I guess, is what I'm trying to say. Yes, there's
22:33
Speaker 1: your T shirt. Trusses rock. So are we at arches?
22:39
Speaker 1: Do we say that they frequently used trusses to support
22:42
Speaker 1: beam bridges? Yeah? Arches. Now, when we say a bridge
22:48
Speaker 1: is an arch bridge, the deck is not some big
22:52
Speaker 1: hill that you drive over. The deck is flat the
22:55
Speaker 1: arches underneath, uh right yeah. And you can have a
23:01
Speaker 1: single arch if your span isn't along, or you can
23:04
Speaker 1: have a big one with like six or eight arches.
23:07
Speaker 1: Although I've seen I think there are like short arch
23:10
Speaker 1: bridges that actually do go up and down, you know,
23:13
Speaker 1: like if there's natural arch bridges, like rock formations are
23:17
Speaker 1: like that and that's why they're still standing. There's um
23:20
Speaker 1: there's there's a bridge that forms like a perfect circle.
23:26
Speaker 1: So like when when you see it reflected in the water,
23:28
Speaker 1: it just looks like a circle. Arch bridges are pretty
23:33
Speaker 1: cool too. There are no trusses, but they're beautiful in
23:36
Speaker 1: their own way. That's true. Uh So the arches obviously
23:40
Speaker 1: semi circular. Um. And like you said, if it meets
23:43
Speaker 1: the water and reflects nicely, fully circular, fully circular. Uh
23:47
Speaker 1: And the entire form is gonna divert weight onto what
23:51
Speaker 1: are called abutments. And this is what takes on the pressure.
23:55
Speaker 1: It's like, I mean, if it's just a single arch,
23:57
Speaker 1: those abutments are probably going to be part of the
23:59
Speaker 1: earth on one side or the other. Yeah. Um. And
24:04
Speaker 1: the whole point of an abutment is when you press
24:07
Speaker 1: down in an arch, or when you know, gravity pushes
24:10
Speaker 1: down on it or it's compressed, that force goes downward
24:15
Speaker 1: and it makes the sides of the arch go out.
24:17
Speaker 1: Those abutments press inward, so that the force of compression
24:22
Speaker 1: just goes straight down through the arch circle the semicircle
24:26
Speaker 1: and into the earth or into the ground or whatever. Yeah.
24:29
Speaker 1: And and it's the arch. The what I thought was interesting,
24:32
Speaker 1: it's really all about fighting that compression. There isn't a
24:35
Speaker 1: lot of tension that comes into play with an arch bridge.
24:39
Speaker 1: I think the tension is grows more and more possible
24:42
Speaker 1: when the degree of the arc or arch grows. Okay, yeah,
24:48
Speaker 1: so that could come into play. It can, but for
24:50
Speaker 1: the most part, when you're building an arch, you have
24:53
Speaker 1: to worry about compression more than tension, gotcha. So there's
24:56
Speaker 1: a stylistically and artistically design wise. They're all kinds of arches.
25:01
Speaker 1: Baroque arches, Renaissance arches, Roman arches. They were the Romans built,
25:07
Speaker 1: you know, arch bridges that are still standing today. Um,
25:10
Speaker 1: have you been to Rome? Yeah? Man, it's just like
25:13
Speaker 1: you're walking along and all of a sudden you look
25:15
Speaker 1: to your leaps and there's like a two thousand year
25:18
Speaker 1: old aqueduct, you know, hundred year old arch just sitting there. Yeah.
25:23
Speaker 1: I remember the first time I went to Europe coming
25:25
Speaker 1: back and being sort of like bummed out, you know,
25:28
Speaker 1: because we're walking along and then there's Burger king. You know,
25:32
Speaker 1: this is two hundred years old. She go to Rome.
25:37
Speaker 1: I know, my house is like eighty years old, and
25:39
Speaker 1: it seems super old. Nothing by Romans standards. No, but
25:45
Speaker 1: you know, a little drafty in those thousand year old apartments. Yeah,
25:48
Speaker 1: but it's so neat though, because I mean like there's
25:51
Speaker 1: so much old surviving stuff that not all of it's
25:55
Speaker 1: even meant to be preserved. Some of it's just like
25:59
Speaker 1: just there. It's not like a part of a park
26:01
Speaker 1: or an historic exhibit. It's just part of the city. Yeah,
26:05
Speaker 1: you know, Yeah, I've heard other tourists complaining about how
26:09
Speaker 1: dirty Rome is, and I'm always just like, come on,
26:13
Speaker 1: it's like focusing on the wrong part. It's been around
26:16
Speaker 1: for a long time. Um yeah. And also yeah, don't
26:21
Speaker 1: be stupid and just look around you like they're complaining
26:25
Speaker 1: in front of a two thousand year old fountain. I
26:26
Speaker 1: didn't notice that was particularly dirty. I mean, it wasn't
26:30
Speaker 1: any more dirty than like New York or anything any
26:33
Speaker 1: other big city. But the thing with the arch though
26:37
Speaker 1: very stable once you get it built. But the building
26:40
Speaker 1: process it's tricky because until you connect those two ends, um,
26:46
Speaker 1: that's what gives it its strength. So until that happens,
26:48
Speaker 1: it's a little dicey. Yeah. Oh yeah, I had some
26:51
Speaker 1: scaffolding come on time. Yeah. And they used to build
26:53
Speaker 1: wood scalf scaffolds and supports to hold the thing and
26:57
Speaker 1: then you just would build it in. Um. Now they
27:00
Speaker 1: use suspension cables like I think the biggest arch bridge
27:05
Speaker 1: on the planet is West Virginia's New River Gorge Bridge,
27:09
Speaker 1: and that thing is unbelievable. It really is. And what's
27:12
Speaker 1: cool is when you look at it, UM, it just
27:15
Speaker 1: it uses the cliff walls or the walls of the
27:18
Speaker 1: gorge as the abutments. Beautiful stuff, super strong. And that's
27:22
Speaker 1: where we're going to talk about that in our base dumping.
27:26
Speaker 1: I know. That's the fact that ties these two podcasts together.
27:29
Speaker 1: It's where they have Bridge Day talk about elegantly simple.
27:34
Speaker 1: So suspension bridges, for my money, are where it's at.
27:38
Speaker 1: I think they deserve their own UM episode. Oh yeah, pretty,
27:43
Speaker 1: I'm pretty much they're they're that complex. Like this is
27:47
Speaker 1: just the briefest overview of bridges in general, but especially
27:51
Speaker 1: with suspension bridges. It feels like there's just so much
27:54
Speaker 1: going on with those things. Yeah, I agree. I mean,
27:57
Speaker 1: Kim Burns did like an eight hour long documentary the
28:00
Speaker 1: Brooklyn Bridge alone. Yeah, that's true. He's a deep diver.
28:05
Speaker 1: We're over of you guys with a giant helmet to
28:08
Speaker 1: go over his giant haircut, because a pretty big hair
28:12
Speaker 1: doan UM. All right, So suspension bridges we mentioned, of course,
28:16
Speaker 1: Golden Gate Bridge and the Brooklyn Bridge. This is when
28:19
Speaker 1: you have your deck, your roadway is suspended by cables
28:25
Speaker 1: between can be a number of them, but uh to
28:29
Speaker 1: at least two tall towers that are supporting all of
28:32
Speaker 1: this weight and compression is pushing down, traveling up through
28:36
Speaker 1: those cables and transferring all that compression through all those
28:40
Speaker 1: lovely cables. Right. So, I mean another way to look
28:43
Speaker 1: at it is exactly what it sounds like. It's the
28:45
Speaker 1: bridge is suspended from cables, right, But if you really
28:49
Speaker 1: start looking into what it's doing, it's not just holding
28:52
Speaker 1: these things up. What's what's going on is there's a
28:55
Speaker 1: transfer of that natural compression of the deck up through
28:59
Speaker 1: the lines, up through the cables up down up to
29:03
Speaker 1: the towers, which, like you said, send them down to
29:05
Speaker 1: the earth. Right, So the towers that hold the bridge
29:09
Speaker 1: up are at the same time distributing or dissipating the
29:14
Speaker 1: forces of compression that are trying to pull the bridge
29:17
Speaker 1: down into the water below it. Yes, and the tension
29:21
Speaker 1: you also have to deal with as well, and apparently
29:24
Speaker 1: you deal with that using another part of the structure
29:27
Speaker 1: of suspension bridges, which are called anchorages. Yeah. Now, that's
29:31
Speaker 1: just what the towers connected to at the base right now. No,
29:35
Speaker 1: huh so it's like um anchorages is like the abutment essentially. Yes,
29:40
Speaker 1: they're they're like a suspension bridges abutments. Whereas as you
29:44
Speaker 1: get closer to the middle of the bridges, that's where
29:46
Speaker 1: the towers are. But on the very ends, like say
29:49
Speaker 1: where the roadway hits the bridge, you're gonna have a
29:52
Speaker 1: massive piece of rock or massive piece of concrete, and
29:56
Speaker 1: those are the anchorages. And you have horizontal cables that
30:02
Speaker 1: distribute the compression from the bottom of the bridge to
30:06
Speaker 1: um the anchorages and those those transfer those into the earth. Yeah.
30:11
Speaker 1: And you might also, depending on the size of your
30:13
Speaker 1: suspension bridge, have to have that below deck truss as
30:17
Speaker 1: well to help stiffen the deck um. And you know,
30:20
Speaker 1: if you have a four thousand foot bridge, you're gonna
30:23
Speaker 1: have all all kinds of trusses and decks and cables.
30:27
Speaker 1: And I think I finally figured out what it is
30:30
Speaker 1: about bridges that I love is that the the arc,
30:34
Speaker 1: the structural design that it needs to be strong, also
30:38
Speaker 1: happens to be beautiful. Yeah, you know what I mean,
30:42
Speaker 1: Like the way the cables are arranged. It's not like
30:44
Speaker 1: they're like, oh, this looks great. It's like, well it
30:46
Speaker 1: has to be like this, but it also happens to
30:49
Speaker 1: be very striking, like Grace Jones, you know what I mean? Yeah,
30:55
Speaker 1: absolutely so. Um So, suspension bridges are your favorite, huh.
31:00
Speaker 1: I like them because they have so much going on.
31:03
Speaker 1: I like trust is because they're so elegantly simple and
31:06
Speaker 1: they're just tough as nails. There's a bridge for everyone.
31:08
Speaker 1: I think there really is. Um the cable stayed bridge,
31:12
Speaker 1: and we should say that suspension bridges. When you think
31:15
Speaker 1: of a suspension bridge, probably probably think of the Golden
31:18
Speaker 1: gate bridge or something like that. Right, Just a classic
31:20
Speaker 1: suspension bridge, two towers to um anchorages, lots of suspension cables.
31:26
Speaker 1: It's the suspension bridge and you think, well, then they're
31:29
Speaker 1: probably pretty new. Wrong. Suspension bridges have been found in
31:34
Speaker 1: various forms for hundreds of years at least, and apparently
31:38
Speaker 1: the Inca were um masters at building rope suspension bridges
31:43
Speaker 1: out of woven grass. Crazy man, Yeah, fifteen hundreds they
31:47
Speaker 1: discovered the Spanish concreteadores stumbled upon these were like, what
31:51
Speaker 1: in the world is going on here? Because the smart
31:54
Speaker 1: Europeans didn't figure this out for another like few hundred
31:57
Speaker 1: years after that. That's right. Um, the inc Is still
32:01
Speaker 1: have one of these bridges intact. It it spans ninety
32:04
Speaker 1: ft um and they remake it every year as part
32:08
Speaker 1: of a three day festival. Really nice, which is why
32:11
Speaker 1: it's still intact because the grass woven grass rope bridge
32:15
Speaker 1: didn't last all that long necessarily even though why when
32:19
Speaker 1: it's fresh and new, it's strong as an expiration date
32:22
Speaker 1: what you're saying. But apparently, as we'll learn, all bridges
32:26
Speaker 1: have an expiration date. All right, Well we'll take a
32:29
Speaker 1: break then with that tease and talk about the cable
32:32
Speaker 1: stayed bridge and then um, how you might die on
32:34
Speaker 1: a bridge one day. Alright, so we're onto your favorite,
32:57
Speaker 1: my friend, the super sleek, modern looking cable stayed bridge,
33:02
Speaker 1: which is actually actually actually has been around since like
33:07
Speaker 1: World War two. Yeah, but the idea which is modern.
33:10
Speaker 1: The idea came from a dude named um Fast Ranchica
33:15
Speaker 1: Man and he was a contemporary of Kepler and brahi
33:19
Speaker 1: Um and he basically came up with the first design
33:23
Speaker 1: for a cable stayed bridge back in the sixteenth century.
33:26
Speaker 1: So what's what's the nuts and bolts of this thing.
33:29
Speaker 1: So basically it is a rather than two towers like
33:34
Speaker 1: a suspension bridge uses, a cable state bridge uses one tower.
33:37
Speaker 1: Well not always um, there's plenty of them that have
33:40
Speaker 1: more than one, but okay, but for a particular span
33:44
Speaker 1: of bridge, there's one tower supporting that one span, right, UM.
33:48
Speaker 1: So it's basically you can't use it for as long
33:51
Speaker 1: of a span as a suspension bridge. But if you
33:54
Speaker 1: have a slightly shorter span and you don't want to
33:56
Speaker 1: spend quite as much money and you don't want as
33:59
Speaker 1: many wires up there and everything, you can go with
34:01
Speaker 1: the cable state bridge. So you have one usually one
34:05
Speaker 1: UM tower holding up all the cables, and the cables
34:09
Speaker 1: can either all connect to one point, which is called
34:13
Speaker 1: a UM radio pattern. Right, So it's like all these
34:19
Speaker 1: different cables are connecting on the bridge deck at different points,
34:23
Speaker 1: but they're all connecting at about a single point on
34:25
Speaker 1: the tower. Again architecturally lovely, very neat looking. And then
34:30
Speaker 1: another way that you can do it is UM in
34:32
Speaker 1: a parallel pattern. So they're connected at different points on
34:35
Speaker 1: the deck and they connect at different points on the tower.
34:39
Speaker 1: And that's the case with the Erasmus Bridge, which I
34:43
Speaker 1: think is the most beautiful bridge in the world in Holland.
34:46
Speaker 1: Well that doesn't surprise me. I mean, look at that thing.
34:49
Speaker 1: Look at that pal Oh yeah, it's something else. Yeah,
34:53
Speaker 1: I wish you guys could see this. Look. It doesn't
34:56
Speaker 1: look like very Dutch though, No, it looks very Um
35:02
Speaker 1: it's like the New Holland. I guess, yeah, new Amsterdam.
35:06
Speaker 1: I'm just picturing like Holland. I think of uh, you know,
35:09
Speaker 1: wooden windmills and like two lips and stuff like that. Ye. Sure, yeah,
35:13
Speaker 1: this is modern hauland for it looks like something that
35:15
Speaker 1: would be in like Sydney, Australia. Well, they have great
35:17
Speaker 1: bridge to they do. Maybe that's what I'm thinking, Um,
35:22
Speaker 1: living bridge, Well, you are you done with those? Well
35:24
Speaker 1: I was gonna say another design for cable state bridge
35:26
Speaker 1: looks a lot like a sailboat, with the tower standing
35:32
Speaker 1: straight up and then on each side cables going down
35:35
Speaker 1: at a diagonal from it to make it look like
35:37
Speaker 1: a sailboat, sail and masked and again for structural integrity
35:41
Speaker 1: more than anything, right, um living bridges sure, Uh, well,
35:47
Speaker 1: I guess we should say cable state bridges are uh
35:50
Speaker 1: they can't be as long as suspension bridges, but they
35:53
Speaker 1: can be pretty long. Yeah, like have to close to
35:56
Speaker 1: three thousand feet. But that's what I'm saying, Like, if
35:58
Speaker 1: you have a shorter span and you don't want to
36:01
Speaker 1: use as many materials and hints, you spend as much
36:04
Speaker 1: money at cable State bridge is a great alternative. Yeah.
36:06
Speaker 1: I wonder when cities, Uh, I wonder what the considerations are, um,
36:11
Speaker 1: like money, what you I would guess money first and
36:14
Speaker 1: foremost money, what you probably is best for the land.
36:18
Speaker 1: And but I also bet that that architecture comes into play,
36:22
Speaker 1: like how it looks in the city escape, don't you think,
36:25
Speaker 1: Like usually a city will have some sort of well
36:28
Speaker 1: accept several designs, competing designs, and then probably well like
36:33
Speaker 1: in Atlanta's case with the seventeenth street bridge, goes with
36:36
Speaker 1: the cheapest one and then half of it falls down
36:39
Speaker 1: on the traffic later, like a couple of years later.
36:41
Speaker 1: Did that happen? Yeah? Uh when um like to two
36:46
Speaker 1: years ago? Really yeah, man, it was a big deal.
36:48
Speaker 1: Luckily it happened at like four in the morning or
36:51
Speaker 1: five in the morning. But like when you're walking on
36:53
Speaker 1: the bridge, you know the side stuff one whole side
36:58
Speaker 1: fell over onto seventy below, onto the onto the connector
37:02
Speaker 1: right below. Yeah, I kind of remember that. Yeah, but
37:05
Speaker 1: it's an ugly bridge to begin with. Three million. Dude,
37:07
Speaker 1: if you're listening the guy who designed it, I'm sorry,
37:09
Speaker 1: I don't mean to insult your work, but I but
37:13
Speaker 1: do better. It just the city could have done better,
37:16
Speaker 1: I think. But I think what it came down to,
37:18
Speaker 1: I'm sure it was. All of these are beautiful, but
37:22
Speaker 1: we're just going to spend the money on this one,
37:24
Speaker 1: you know, or whoever got the biggest kick back or
37:27
Speaker 1: wherever that came from, not to be cynical. Living bridges. Yeah,
37:33
Speaker 1: we're talking about that. Um. If you go to northern
37:37
Speaker 1: India to the here we go, uh, the Meghalaya region,
37:42
Speaker 1: I think that was good. All right, close enough, Um,
37:46
Speaker 1: they have something pretty remarkable and they are called living bridges.
37:50
Speaker 1: And what they did was it's so rainy there that
37:54
Speaker 1: all of their natural bridges were having a hard time
37:56
Speaker 1: staying intact because of all the moisture from monsoons. Yeah,
38:00
Speaker 1: and that's you know, you can't have a natural bridge
38:02
Speaker 1: with that much water. So they said, why don't we
38:06
Speaker 1: take these tree roots and grow them out of the
38:11
Speaker 1: ground and span a river over the course of years
38:15
Speaker 1: and years and years and then basically plant on the
38:19
Speaker 1: other side into the ground and this is now a
38:22
Speaker 1: natural tree root bridge. Right, it's like giant living bonds.
38:25
Speaker 1: I like you're they were training routes to go a
38:28
Speaker 1: certain way, and they would take a um, a tree,
38:31
Speaker 1: a felled tree, and split it in half and use
38:34
Speaker 1: that as the guide. Right, it's like the structure so
38:37
Speaker 1: that they were building an arch, but they weren't making
38:39
Speaker 1: an arch like sort of a temporary bridge exactly, and
38:42
Speaker 1: they let the roots grow along that and like they
38:44
Speaker 1: would plan these things out, or they do plan these
38:46
Speaker 1: things out over the course of like a decade. And
38:49
Speaker 1: I get the impression it's, um, the whole town's responsibilityly,
38:52
Speaker 1: some people in the town's responsibility to make sure that
38:55
Speaker 1: if you see your route starting to go down in
38:57
Speaker 1: the wrong place, you just pluck it up and put
38:59
Speaker 1: it back on a fell log that's guiding it across
39:02
Speaker 1: the way. Yeah, it's pretty neat, like it requires patients obviously,
39:05
Speaker 1: but it also um, I imagine just once a day
39:09
Speaker 1: someone walks down and it's like yep, looking good, and
39:12
Speaker 1: then just walks away again, pets. The bridge says, keep growing,
39:15
Speaker 1: I'll walk across in ten years, buddy. And apparently those
39:18
Speaker 1: things can last up to fifty years or the the
39:21
Speaker 1: largest one that they have up to a hundred feet,
39:24
Speaker 1: which is thirty meters for our friends in India. Um,
39:27
Speaker 1: and it can bear the way to fifty people and
39:30
Speaker 1: last up to five years, not fifty. That's what I said. Oh,
39:33
Speaker 1: I thought you said people, well, it's crazy, like you
39:38
Speaker 1: gotta google these things. Yeah, they're very pretty, very pretty.
39:42
Speaker 1: It looks very um dark crystally. Oh yeah, totally, you
39:47
Speaker 1: know what I mean. But they're not unsettling at all
39:50
Speaker 1: like the dark crystal right, which, by the way, if
39:53
Speaker 1: you're ever in Atlanta, sometimes people say, Hey, I'm coming
39:56
Speaker 1: to Atlanta. What should I do? Uh, go to the
39:59
Speaker 1: Center for Popetry Arts and just look at their free exhibit,
40:03
Speaker 1: which includes a full size Skexy. It's terrifying. Yeah, they
40:08
Speaker 1: have We've talked about this before. They have emmett Utter.
40:13
Speaker 1: For me, that was pretty pretty magnificent. It meant a
40:16
Speaker 1: lot for Emma Utter to meet you too. They're doing
40:19
Speaker 1: Actually I saw it was just at the Museum of
40:21
Speaker 1: the Moving Image and Queens. Oh, yeah, I saw you
40:24
Speaker 1: post something about that. Yeah, they have a Madman exhibit
40:26
Speaker 1: right now, which is pretty neat, but it was they
40:30
Speaker 1: I was not there in time for the Jim Henson
40:32
Speaker 1: when they're they're putting that in place, I think for
40:34
Speaker 1: later coming coming. What's good You didn't miss it yet? Well, yeah,
40:38
Speaker 1: I'll just go back. We went to the Yoko on
40:41
Speaker 1: No exhibit at Momah. Awesome. She's something else, dude. She's
40:46
Speaker 1: got a pretty cool mind. Yeah, she had She had
40:50
Speaker 1: this one display and it was titled three Spoons and
40:54
Speaker 1: it was just four spoons in a row. It wasn't three.
40:59
Speaker 1: I love that stuff, so I recommend that as well.
41:03
Speaker 1: I'm not a fan of her music, though, I actually
41:05
Speaker 1: got turned onto her music in the listening room there
41:07
Speaker 1: Plastic Band. It's crazy. It's weird stuff, but I kind
41:11
Speaker 1: of like it. I mean, she's definitely one of the
41:13
Speaker 1: most like original thinkers you know out there, and she's
41:18
Speaker 1: been at it for a while, like a lot of
41:19
Speaker 1: the stuff went back to the sixties, like the early sixties. Yeah,
41:22
Speaker 1: and talk about weathering criticism and still just being like
41:25
Speaker 1: screw you. Yeah, I'm Yoko. Oh No, I don't care
41:28
Speaker 1: what you say. Well she was exonerated to recently, remember
41:31
Speaker 1: Paul McCartney came out and said like, it was not
41:33
Speaker 1: Yoko owner that broke up the Beatles and saying that
41:36
Speaker 1: it just took him like fifty years to come out
41:38
Speaker 1: and say it. Yeah, she's like, would it kill you? Right?
41:43
Speaker 1: He told me privately many times, but we'll press release,
41:46
Speaker 1: tweet it alright. So we talked about compression and uh
41:52
Speaker 1: tension being the two main forces. Uh, there are quite
41:55
Speaker 1: a few other forces, dozens even they can act on
41:58
Speaker 1: a bridge in a negative way, And the scariest one,
42:01
Speaker 1: for my money, is torsion. Um. If you've ever seen
42:05
Speaker 1: the video, it's a very famous video of the bridge,
42:10
Speaker 1: what is it the Tacoma the Tacoma Narrows Bridge to
42:13
Speaker 1: coma narrows bridge when it looks like a wet noodle
42:17
Speaker 1: twisting in the wind, Yeah, it was. It's nuts. And
42:20
Speaker 1: they have like footage of this whole thing just undergoing
42:23
Speaker 1: this destruction that kept just going on and on and
42:27
Speaker 1: on and finally the bridges comes down. Yeah. The craziest
42:30
Speaker 1: part is when you're watching it, you just think, oh man,
42:32
Speaker 1: look at that thing. It's nuts, and thank god, there's
42:34
Speaker 1: no one on it, and then you see I continude
42:36
Speaker 1: walking on it in a car. Yeah, and a guy
42:39
Speaker 1: ran there was a dog. There's one car in there
42:41
Speaker 1: and there's a dog trapped in the car, and some
42:44
Speaker 1: guy ran and got the dogs. Yes, pretty great heroic stuff. Sure.
42:49
Speaker 1: Then later on I don't know if he's the same
42:51
Speaker 1: guy and another guy or just two completely new guys.
42:54
Speaker 1: They're just walking along it. This is after a whole
42:56
Speaker 1: section is falling into the river, but the section they're
42:59
Speaker 1: walking still swaying way from the bridge. Step back from
43:05
Speaker 1: the bridge, man, So that's torsion at work. Yeah, and
43:09
Speaker 1: that's a big problem that designers a suspension bridges face
43:12
Speaker 1: because you have a deck that's being held from being
43:16
Speaker 1: held alof by cables. Right, it's not like fixed to
43:20
Speaker 1: anything below it necessarily mean it's being suspended. So just
43:24
Speaker 1: like on like a rope bridge or something like that,
43:27
Speaker 1: it sways very easily. Right. Yeah, those towers are strong,
43:30
Speaker 1: but it's not, you know, directly connected to those towers.
43:34
Speaker 1: So if you have a swaying bridge in between them, right,
43:39
Speaker 1: and the thing is swaying back and forth, but if
43:42
Speaker 1: one side starts to sway over the other side and
43:45
Speaker 1: all of a sudden you have an opposing circular force,
43:48
Speaker 1: and that's torsion, and that can basically rip the bridge
43:52
Speaker 1: in into which is sheer. Yeah. Well that's the other
43:57
Speaker 1: awful thing that can happen. It can just snap, well
44:00
Speaker 1: not snap, I guess, but just breaking to two parts. Yeah. Well,
44:04
Speaker 1: I mean snapping is the result of compression. Sharing would
44:08
Speaker 1: be what it's called technically, where to the same span
44:13
Speaker 1: of bridge has the two opposing forces acting on it
44:17
Speaker 1: at once, UM, in opposite directions, and it goes it
44:21
Speaker 1: makes that terrible sound. Um. If you want to combat torsion, UM.
44:27
Speaker 1: Many ways to do this, You're you're probably gonna have
44:29
Speaker 1: a deck trust going on to help out. Trust saves
44:33
Speaker 1: the day that trust saves the day you're gonna have.
44:36
Speaker 1: You're gonna do wind tunnel tests if it's a modern
44:40
Speaker 1: bridge beforehand, well you're gonna make a model, yeah, and
44:44
Speaker 1: do tests and see like how does wind affect this
44:46
Speaker 1: bridge and what do we need to do. But the
44:48
Speaker 1: thing is with the um with the Tacoma Narrows Bridge
44:53
Speaker 1: in particular, they did tests. They had that thing rated
44:57
Speaker 1: with standing winds up to a hundred and twenty was
45:00
Speaker 1: an hour. But the winds that day that brought it down.
45:03
Speaker 1: We're only forty miles an hour, And for a long
45:06
Speaker 1: time they were like, what happened, and somebody said, you
45:10
Speaker 1: know what it was? It was mechanical residence. It was. Yeah,
45:15
Speaker 1: the deck trust was not sufficient for the span that
45:20
Speaker 1: was part of it and the way that the wind
45:22
Speaker 1: hit it and the angle calls the final thing that
45:25
Speaker 1: you just mentioned residents, which is um sort of it's
45:29
Speaker 1: a vibration basically that gets out of hands. So resonance,
45:32
Speaker 1: to me, I think deserves its own podcast too. It's awesome.
45:36
Speaker 1: Everything every especially anything that we build, from an airplane
45:39
Speaker 1: to a bridge, to watch it has a certain frequency
45:45
Speaker 1: um where it will really pick up force, really absorbed force,
45:50
Speaker 1: it will run through it. Right, So let's say that
45:52
Speaker 1: your bridge um has a residence. Uh, that's like at
45:56
Speaker 1: a frequency of ten. That's probably a total the ridiculous
46:00
Speaker 1: number that I just said. But let's say it's ten, right,
46:03
Speaker 1: and then let's say that wind comes at it at
46:05
Speaker 1: fort at just the right angle and it makes it
46:08
Speaker 1: sway at a frequency of nine, Well, that bridge is
46:11
Speaker 1: gonna be It's just gonna sit there and sway. Not
46:14
Speaker 1: a big problem. If that wind hits it at just
46:16
Speaker 1: the right angle at just the right speed it's and
46:18
Speaker 1: it starts swaying at eleven, it's still not quite a problem.
46:23
Speaker 1: But if it gets it just right and it starts
46:25
Speaker 1: it swaying at ten, all of a sudden, those sways
46:28
Speaker 1: are going to become more and more pronounced because all
46:30
Speaker 1: that energy is flowing through at its maximum potential and
46:35
Speaker 1: at its freest flow, because it's hitting the bridge at
46:39
Speaker 1: its natural residence, right. And that's what caused the Tacoma
46:44
Speaker 1: Narrows Bridge to come down, because once that thing starts going,
46:48
Speaker 1: there's no coming back from it because it's just happening.
46:51
Speaker 1: It gets worse and work exactly. And that's that's because
46:54
Speaker 1: it hit it at just the right frequency. Yeah, they
46:56
Speaker 1: like in it in the article, which I think is
46:58
Speaker 1: pretty uh down to earth, the snowball rolling downhill exactly.
47:02
Speaker 1: It just keeps getting worse and worse, and that you
47:04
Speaker 1: can't stop it. So but isn't that bizarre that you
47:07
Speaker 1: a bridge has a natural residence and natural frequency. I
47:11
Speaker 1: don't think so, Like I would assume it would vibrate. Yeah,
47:15
Speaker 1: it did not occur to me at all. And I
47:17
Speaker 1: was talking to Adam about this too, And I was like,
47:20
Speaker 1: so I saw that building designers, bridge designers, they will
47:24
Speaker 1: fine tune like a structure so that it resonates at
47:29
Speaker 1: a frequency that it's probably never gonna encounter from an
47:32
Speaker 1: earthquake or from winds or whatever. I'm like, how do
47:35
Speaker 1: you do that? And apparently it comes down to the
47:38
Speaker 1: building materials you use, the shapes you use to form
47:41
Speaker 1: the structure, the way you join those shapes together. And
47:46
Speaker 1: you can basically say, I'm giving this building a frequency
47:50
Speaker 1: of one point five, whereas I know all of the
47:54
Speaker 1: wind in the area and the ground movement from an
47:57
Speaker 1: earthquake is going to make it vibrated a free quency
48:00
Speaker 1: of seven, so it'll be fine. Yeah. And one way,
48:04
Speaker 1: like you said, they can do that is by not
48:06
Speaker 1: having like one like shortening the sections of the deck
48:09
Speaker 1: plus a and that way the vibration. When you have
48:13
Speaker 1: these overlapping plates and smaller sections, it's gonna create enough
48:17
Speaker 1: friction to disrupt that frequency. Right, it'll change the frequency
48:20
Speaker 1: that the bridge is moving at. But I mean, and
48:22
Speaker 1: not just bridges, to you have to take this into
48:24
Speaker 1: take into account like airplanes, right, you can't use engines
48:28
Speaker 1: on airplanes that create vibrations at a frequency that's at
48:32
Speaker 1: the natural resonance of the airplane body. Most the airplane
48:36
Speaker 1: body is gonna come apart just from turning the engines on.
48:39
Speaker 1: Could you imagine seeing the airplane wings starting to flap
48:42
Speaker 1: like harder and harder, Right, But apparently the more common
48:46
Speaker 1: thing when you have a disaster catastrophe from a residents
48:50
Speaker 1: a mechanical resonance problem. Um, it's like one bolt, it's
48:54
Speaker 1: like I can't take it anymore and stops, and then
48:56
Speaker 1: that leads to a cascade of failures that aultimately has
49:01
Speaker 1: the bridge coming down. Interesting. I think that's fascinating. I
49:05
Speaker 1: had no idea that you had to worry about frequencies
49:08
Speaker 1: and vibrations. Why all the bridges you've built of collapse?
49:12
Speaker 1: They collapsed pretty easy. Well, if you've ever heard the
49:15
Speaker 1: old they go down like a French boxer. That means
49:20
Speaker 1: I don't need um. But it was a glass Joe reference.
49:23
Speaker 1: Remember him from Tyson's punch out, Oh No counter He
49:29
Speaker 1: says he was French glass joe. You said, a glass
49:33
Speaker 1: jaw and he went down just like a sack of potato,
49:36
Speaker 1: so easy. Well, which was it a sack of potatoes?
49:39
Speaker 1: Or a French boxer. He was both. He went down
49:43
Speaker 1: like a sack of French potatoes. Yes, French fries. My
49:46
Speaker 1: bridges go down like a French boxer. But Glass Joe,
49:50
Speaker 1: the French boxer went down like a sack of potatoes. Ergo,
49:53
Speaker 1: my bridges go down like a sack of potatoes. Um,
49:58
Speaker 1: if you've ever heard the Old Wives stay all that
50:00
Speaker 1: like an army marching across the bridge and step can
50:04
Speaker 1: cause enough vibration to take down that bridge. It's true
50:08
Speaker 1: that could happen. So if at the right frequency, right yeah,
50:12
Speaker 1: and wartime, that's they will break step. In other words,
50:15
Speaker 1: their rhythm isn't all the same to avoid that scenario.
50:19
Speaker 1: And there was a bridge disaster I saw on that
50:21
Speaker 1: Time magazine slide show where that happened. Um, there were
50:26
Speaker 1: there were a pair of skywalk bridges inside the Higher
50:29
Speaker 1: Regency Kansas City Hotel, um in the lobby. They were
50:34
Speaker 1: just like you know, raised bridges going through the lobby,
50:38
Speaker 1: and they collapsed and killed like a bunch of people
50:42
Speaker 1: because people people marching dancing. They were dancing on the
50:47
Speaker 1: on the skywalk. And you think, like up to today
50:51
Speaker 1: or yesterday when I started researching this right, Like, I
50:55
Speaker 1: just thought that's weight or pressure, something like if everybody's dancing,
50:59
Speaker 1: didn't It never occurred to me that the rhythm had
51:03
Speaker 1: something to do. Yeah, i'd always heard that, Well, you're
51:06
Speaker 1: far more advanced than I am a structural engineering, my friend.
51:09
Speaker 1: Not that. It's just always heard that, like, you know,
51:11
Speaker 1: even a bunch of kittens walking across could cause that.
51:15
Speaker 1: And the reason they said kittens, of course, is so
51:17
Speaker 1: it has nothing to do with weight, right, because kittens
51:20
Speaker 1: knowing nothing. And consequently, I think Lina Richie had to
51:24
Speaker 1: change the name of that song because of the accident.
51:26
Speaker 1: I think originally it was what a feeling when you're
51:28
Speaker 1: dancing on the skywalk and he had to change it
51:32
Speaker 1: to ceiling and everyone's like, that's weird dance on the ceiling,
51:35
Speaker 1: but it rhymes, and he's like, yeah, but nobody ever
51:38
Speaker 1: died from dancing on this on the ceiling. I guess
51:41
Speaker 1: the final thing we should mention is that weather. Um,
51:45
Speaker 1: obviously we'll play a big impact. We already talked about wind,
51:48
Speaker 1: but um, over the years, the materials they use in
51:52
Speaker 1: the design is gone in to take account things like
51:55
Speaker 1: wind and uh what sun damage. I don't know what
51:59
Speaker 1: I think get the free stall cycles, huge salt salt exposure.
52:04
Speaker 1: If it's going over like a salty body of water,
52:07
Speaker 1: that makes sense. Yeah, there's a lot of things that
52:10
Speaker 1: are trying to bring a bridge down. Nature abhores a
52:13
Speaker 1: bridge basically as much as a vacuum um. I've going
52:18
Speaker 1: what's got. There's probably around six hundred and thirty thousand
52:22
Speaker 1: bridges in the US alone, because there were six hundred
52:26
Speaker 1: and seventeen thousand, nine hundred and thirty five and a
52:28
Speaker 1: two thousand two census, and they add them. They were
52:32
Speaker 1: adding them at about a thousand a year, maybe nine
52:34
Speaker 1: hundred a year. That's just the US. The world's longest
52:38
Speaker 1: bridge completed in two ten, the Danyang Coon Shawn Bridge.
52:43
Speaker 1: I think I've seen pictures of that. It serves as
52:46
Speaker 1: a railway bridge for the Beijing and Shanghai Railway. It's
52:50
Speaker 1: a hundred and two mile long bridge that's nutty over water.
52:54
Speaker 1: I'm a big fan of cities with multiple water bridges.
53:00
Speaker 1: That's why you liked Pittsburgh, Pittsburgh, Portland, Budapest. I'm a
53:05
Speaker 1: big fan. Atlanta. Doesn't mean we have bridges, but it's
53:07
Speaker 1: not like you have to go to the Chattahoochee River Lakes.
53:11
Speaker 1: Nobody goes to the Chattahoochie You know what. Um, I
53:16
Speaker 1: got one more thing I want to shout out to
53:17
Speaker 1: PBS is build it big website, which is like beyond
53:21
Speaker 1: nineties as far as websites go. But it was extremely
53:25
Speaker 1: helpful and understanding the forces that work on bridges, different
53:29
Speaker 1: types of bridges, different specific bridges. Great website and thanks
53:34
Speaker 1: to Adam. I guess you got some information from him. Yeah,
53:36
Speaker 1: thanks Adam. Was he into talking to you about it?
53:38
Speaker 1: Or was he on the other end going oh my god,
53:41
Speaker 1: justsh shut up and watching Tim and Eric? He was
53:43
Speaker 1: he was into talking about it. I figured he would
53:46
Speaker 1: be yeah. Uh. And I actually have to shout out
53:48
Speaker 1: to you mean too because I told her we were
53:49
Speaker 1: building bridges, or well, we were talking about bridges. She
53:52
Speaker 1: sent me a bunch of stuff on popsicle bridges. Um,
53:55
Speaker 1: apparently there's a a Indie Go go for the world's
54:00
Speaker 1: strongest or Canada's strongest popsicle bridge. Yeah, they're trying to
54:05
Speaker 1: build that. Yes, and they start six screened already for
54:11
Speaker 1: out of popsicle sticks. Good for them. So that's everybody
54:15
Speaker 1: getting shouted out to all over the place in this one. Huh,
54:17
Speaker 1: that's nice stuff. Bam. If you want to know more
54:21
Speaker 1: about bridges, you can type that word into the search
54:23
Speaker 1: part how stuff works dot com. And since I said
54:26
Speaker 1: search parts, time for listener mayl. I'm gonna call this.
54:33
Speaker 1: I got a couple of street gang responses. Will read
54:36
Speaker 1: over the next couple of shows. Um, here's one. I
54:40
Speaker 1: had to write in about your street gangs episode as
54:42
Speaker 1: it was interesting pertains to my job. Short version is
54:45
Speaker 1: that I worked for a hospital based program and we
54:47
Speaker 1: see every gunshot wound victim and stab wound victim who
54:50
Speaker 1: comes through, which is about four year UM, and about
54:53
Speaker 1: ten percent of those are gang involved. How you guys
54:56
Speaker 1: have mentioned how you found the number of gangs to
54:58
Speaker 1: be hard to believe, but I think you may you
55:00
Speaker 1: thinking the street gangs is one entity that has strict
55:02
Speaker 1: borders and lots of people. And my experience, larger gangs
55:06
Speaker 1: will sometimes incorporate smaller gangs, and sometimes larger gangs will
55:09
Speaker 1: split off into many many smaller groups. Uh. People go
55:13
Speaker 1: in and out of gangs and are sometimes affiliated with
55:15
Speaker 1: more than one. Currently, we have about at least seventy
55:17
Speaker 1: in our city alone, and a substantial amount of those
55:20
Speaker 1: have less than twenty members, so like many gangs, not
55:23
Speaker 1: super gangs, not super gangs. According to this paper on
55:26
Speaker 1: street gangs in Boston, eight percent of the gangs in
55:29
Speaker 1: the city have less than ten members and have ten
55:33
Speaker 1: to nineteen members. So while the numbers you gave seem
55:38
Speaker 1: shockingly high, they also seem to be in step with
55:40
Speaker 1: the current climate. And that is from Arianna. And what
55:44
Speaker 1: city did she say? You know, I don't see that.
55:46
Speaker 1: I don't think she said. I don't know if it
55:49
Speaker 1: was Boston or if she just referenced Boston. Well, thanks
55:51
Speaker 1: a lot, Ariana. We appreciate that email. And yeah, keep
55:55
Speaker 1: them coming. We wanted them more about gangs. I just
55:57
Speaker 1: had the impression the whole time that like one or another,
56:00
Speaker 1: we were officially or unofficially misinformed. H And also let
56:07
Speaker 1: us know who's the coolest famous person you've ever met?
56:11
Speaker 1: You can tweet to us that that's why sk podcast.
56:15
Speaker 1: You can join us on Facebook dot com, slash stuff
56:17
Speaker 1: you Should Know. You can put it in an email
56:19
Speaker 1: to stuff Podcast at how Stuff Works dot com and
56:22
Speaker 1: has always joined us at our home on the web,
56:24
Speaker 1: Stuff you Should Know dot com. For more on this
56:32
Speaker 1: and thousands of other topics. Is it how stuff works?
56:34
Speaker 1: Dot com