WEBVTT - Selects: Bridges: Nature Abhors Them 0:00:01.160 --> 0:00:04.400 Hello, s y s K Fam. It's Josh and for 0:00:04.519 --> 0:00:08.000 this week's Stuff you Should Know selects. I've chosen Bridges 0:00:08.520 --> 0:00:11.960 Nature Abhores Them, which we released back in June of 0:00:11.960 --> 0:00:14.880 two fift and it's a pretty good one. It's got 0:00:14.880 --> 0:00:17.680 a lot of engineering, believe it or not. But it's 0:00:17.680 --> 0:00:20.439 not like the eye glazy kind. It's like the oh 0:00:20.520 --> 0:00:24.400 my god, this is amazingly fascinating kind. I hope you 0:00:24.440 --> 0:00:26.639 feel that way at least, and I'll bet you will 0:00:27.000 --> 0:00:43.720 so enjoy Bridges Nature Abhores Them. Starting now, welcome to 0:00:43.800 --> 0:00:52.760 Stuff you Should Know, a production of I Heart Radio. Hey, 0:00:52.800 --> 0:00:55.360 and welcome to the podcast. I'm Josh Clark with Charles 0:00:55.400 --> 0:00:59.120 w Chuck Bryant with Jerry Rowland with me Josh Clark, 0:00:59.480 --> 0:01:02.960 and this is You Should Know featuring Josh Clark's about 0:01:02.960 --> 0:01:05.039 to say, you never introduce yourself, and then you done 0:01:05.080 --> 0:01:09.279 did it twice? Three three times? Oh yeah, you always 0:01:09.280 --> 0:01:11.840 introduce your but you never say your last name. I 0:01:11.880 --> 0:01:16.920 think that's extruct me. John, No, I say I'm Josh Clark, 0:01:17.040 --> 0:01:20.000 do you Yeah? Every time I should listen to these sometimes, yeah, 0:01:21.000 --> 0:01:23.880 that explains the glazed overlook in your eyes. Whenever we 0:01:24.000 --> 0:01:32.480 start um Bridges. Yeah, is that your intro? Yep, I 0:01:32.720 --> 0:01:35.200 like him. Maybe we can add like a scat drummer 0:01:35.360 --> 0:01:38.520 on top of that. We have that kind of um 0:01:38.560 --> 0:01:41.440 when we're doing uh listener mail, there's a little bit 0:01:41.480 --> 0:01:44.400 of dan Oh yeah, well that's not scat drumming. I 0:01:44.440 --> 0:01:47.480 would say that's more of a shuffle mhm scats like 0:01:47.480 --> 0:01:51.360 bood Yeah like that. Yeah, you should get Hodgment to 0:01:51.360 --> 0:01:55.400 scat for you sometime. He's going He's get a lot 0:01:55.480 --> 0:01:59.640 of boot boot badus going on when he's scatting any 0:01:59.720 --> 0:02:03.640 jazz hands. No, No, it's not exactly Manhattan transfer level. 0:02:05.160 --> 0:02:13.320 He's intermediate. Yeah. Uh yeah so again Bridges. Yeah, you know, 0:02:13.360 --> 0:02:15.040 I bet we're going to hear from some folks because 0:02:15.080 --> 0:02:19.200 there are bridge enthusiasts Yeah, which I think is kind 0:02:19.200 --> 0:02:22.880 of neat. Yeah. Well, I mean they're like modern marvels 0:02:22.880 --> 0:02:26.160 of engineering, and actually there's some ancient marvels of engineering too, 0:02:26.200 --> 0:02:32.560 as far as they are, um, yeah, they're basically I 0:02:32.639 --> 0:02:37.480 was talking to our pal um Adam the architect o, 0:02:37.520 --> 0:02:42.160 the bridge builder. No, uh, he's a building builder or 0:02:42.240 --> 0:02:44.880 a building designer. I don't know if he actually knows 0:02:44.919 --> 0:02:46.800 how to build the buildings. He just knows how to 0:02:46.800 --> 0:02:49.200 tell other people how to build that. Adam can't swing 0:02:49.200 --> 0:02:56.800 a hammer, so he was saying that, um uh the um. 0:02:57.040 --> 0:03:00.560 Basically the structural engineers who designed bridges are just straight 0:03:00.639 --> 0:03:04.520 up geniuses. Like it requires a basically a genius to 0:03:04.520 --> 0:03:07.120 to factor in all of this stuff. Yeah, anyone can 0:03:07.120 --> 0:03:10.720 design a building, you know, there's just four walls and 0:03:10.720 --> 0:03:13.560 a bunch of floors. Put a roof on it. Bridge 0:03:13.600 --> 0:03:18.440 though it's different. Yes, right, there aren't walls really, Um, 0:03:18.639 --> 0:03:20.960 there can be bridges of Madison County they had walls. 0:03:21.040 --> 0:03:23.560 Oh yeah, they have walls. I was going to mention 0:03:23.560 --> 0:03:26.200 the bridges of Madison County. Yeah, I love those that 0:03:26.200 --> 0:03:31.160 that'd be a beam bridge, I guess, yeah, with a truss, right, 0:03:31.760 --> 0:03:35.560 a top trust, what's the top trust called a through 0:03:35.600 --> 0:03:39.760 trust through trusts, and then below that. If it were 0:03:39.800 --> 0:03:41.760 below it would be a deck trust. But I don't 0:03:41.760 --> 0:03:43.280 know if that counts as a trust. It's more just 0:03:43.320 --> 0:03:45.560 like a house on top of the bridge. I bet 0:03:45.560 --> 0:03:48.240 their structural support there. I guess they thought it was 0:03:48.600 --> 0:03:50.360 mainly just to keep the rain off of you when 0:03:50.360 --> 0:03:53.080 you crossed the bridge, like just an extra little thank 0:03:53.120 --> 0:03:55.080 you for crossing the bridge. I thought it was just 0:03:55.160 --> 0:03:59.040 to draw in Lackey tourists who wanted to have their 0:03:59.040 --> 0:04:02.720 picture made. Another famous bridge, the one that the headless 0:04:02.720 --> 0:04:06.440 Horseman couldn't cross in the Legend of Sleepy Halla. Oh yeah, 0:04:06.560 --> 0:04:10.160 it wouldn't that a bridge. Sure, trolls of under bridges, 0:04:10.440 --> 0:04:14.320 bats drawbridges are pretty cool. Have you ever seen Maximum 0:04:14.320 --> 0:04:17.720 Overdrive the beginning of that movie. Um, it's been many 0:04:17.760 --> 0:04:20.440 many years. I saw it again. I saw it again 0:04:20.520 --> 0:04:23.279 very recently, like this year, and it is it's maybe 0:04:23.360 --> 0:04:25.479 better than it was before. It holds up as a 0:04:25.480 --> 0:04:29.320 crappy movie still. Yes. Yeah. The whole soundtrack is a 0:04:29.400 --> 0:04:31.360 C d C by the way, which you should love 0:04:32.160 --> 0:04:34.080 the whole soundtrack. I do love that, and I do 0:04:34.160 --> 0:04:38.080 remember that. And didn't Stephen King directs that, which he 0:04:38.120 --> 0:04:40.800 doesn't do much right. No, that maybe it's only one 0:04:40.920 --> 0:04:43.800 is definitely his first interesting. But there's a great draw 0:04:44.520 --> 0:04:49.359 drawbridge scene in there. Did someone jump it, jump the 0:04:49.400 --> 0:04:54.039 span as it raised? No, I think their car fell 0:04:54.080 --> 0:04:57.159 into their truck fell in. Okay, because usually the drawbridge 0:04:57.160 --> 0:05:01.360 scene is like I can make it. Uh No, this 0:05:01.400 --> 0:05:06.760 one was You're all doomed and uh. Let me also 0:05:06.760 --> 0:05:10.440 recommend Budapest for bridges. You mean I went to Budapest 0:05:10.440 --> 0:05:12.560 a couple of years ago. Yeah, I went there like 0:05:12.680 --> 0:05:15.919 twenty years ago. Okay, so yeah, you know the bridges 0:05:15.960 --> 0:05:19.040 are amazing that I think like five because they connect 0:05:19.080 --> 0:05:23.840 the two sides. Yeah, Buddha and Pesht, right, and each 0:05:23.880 --> 0:05:27.520 one is totally different, like it's just a completely different design. Yeah, 0:05:27.560 --> 0:05:31.160 and they're just all gorgeous. Yeah, let's just start with 0:05:31.200 --> 0:05:33.960 a bunch of bridge recommendations. I'm going to recommend the 0:05:34.000 --> 0:05:37.359 city of Pittsburgh. Oh yeah, I went through a baseball 0:05:37.440 --> 0:05:40.760 game there, and it's just just gorgeous. Those beautiful bridges 0:05:40.760 --> 0:05:43.479 that you can see from the baseball stadium and the river. 0:05:43.839 --> 0:05:48.680 That was when we were a Toyota commercial from its ring, right. Yeah, 0:05:48.720 --> 0:05:52.719 I stayed in the hotel and just eight um sog 0:05:52.800 --> 0:05:56.039 copenny r no chicken sog. Right, it's just like a 0:05:56.200 --> 0:05:58.760 chord of it. But you can see the baseball stadium 0:05:58.800 --> 0:06:02.599 out your hotel window. Yeah. And I saw some bridges too. Yeah, 0:06:02.640 --> 0:06:04.920 you walk across the bridge to get there. Really, swe 0:06:05.040 --> 0:06:10.080 did what else any other bridges? Well, Brooklyn Bridge, sure, 0:06:10.480 --> 0:06:13.120 Golden Gate Bridge, those are like the famous ones are 0:06:13.160 --> 0:06:16.520 barely even worth mentioning, Yeah, but the Brooklyn Bridge is 0:06:17.360 --> 0:06:20.320 for your money. It's which is free. It's a pretty 0:06:20.320 --> 0:06:22.719 great thing to do to walk across it. It's it's 0:06:22.839 --> 0:06:25.520 just beautiful. I've never done that. You should do it. 0:06:25.720 --> 0:06:28.960 Even the Geico Lizard did it, and I haven't. That 0:06:29.040 --> 0:06:31.400 guy's like Australian or something. Well, maybe we should just 0:06:31.480 --> 0:06:34.280 animate you and have you walk across it. Uh. One 0:06:34.279 --> 0:06:37.240 more thing, if you want to know more about the 0:06:37.240 --> 0:06:39.920 Brooklyn Bridge, I don't remember which one we talked about 0:06:39.960 --> 0:06:43.200 it and but there is a really cool documentary about 0:06:43.200 --> 0:06:47.840 the Brooklyn Bridge and it's building by Ken Burns. Oh wow, 0:06:48.000 --> 0:06:50.320 I believe it's on Netflix. I'll have to check that 0:06:50.360 --> 0:06:54.920 out then, yep, because I like kin Burns and Brooklyn bridges. 0:06:56.120 --> 0:07:01.440 All right, you ready? Uh yeah. In so, bridges have 0:07:01.560 --> 0:07:04.240 been around for a very long time. This article is 0:07:04.279 --> 0:07:07.640 by Robert lam and another dude named Michael Morrissey together. 0:07:08.160 --> 0:07:11.160 I believe they were locked away in a closet for 0:07:11.240 --> 0:07:14.760 like a couple of months while they worked this out together. Well, 0:07:14.920 --> 0:07:16.800 he the one of the first ones that're talking about 0:07:16.840 --> 0:07:21.920 ancient bridges that they mentioned in here. The Arcadeco Bridge 0:07:22.200 --> 0:07:25.840 in ancient Greece, did you see that thing? It's really neat. 0:07:25.880 --> 0:07:28.800 I mean it still stands. It's a three thousand year 0:07:28.840 --> 0:07:32.280 old bridge, and uh, it's just kind of cool to 0:07:32.320 --> 0:07:37.559 think about. You know, ancient civilizations. In ancient times, people said, well, 0:07:38.240 --> 0:07:40.480 I want to get over there, right and I'm here, 0:07:41.400 --> 0:07:43.680 and uh so let's build something to do that. I 0:07:43.680 --> 0:07:46.800 need something to walk on, yeah, or drive my card over? 0:07:47.200 --> 0:07:50.240 Is that simple? Um? I saw that. I saw the 0:07:50.280 --> 0:07:54.120 world's oldest bridge that's still in use, um Is in 0:07:54.200 --> 0:08:00.600 Turkey over the um Melis River, I believe, from eight 0:08:01.000 --> 0:08:03.080 b c. Do you know what that one's h How 0:08:03.080 --> 0:08:09.720 it's constructed a single It is a single stone slab archy. No, 0:08:09.880 --> 0:08:13.760 it is a stone slab, single arch. Yeah, that makes sense, 0:08:14.920 --> 0:08:21.280 very basic. Yeah, but the arch it's super old. But 0:08:21.320 --> 0:08:25.480 it's still in use today because whoever figured it out 0:08:25.680 --> 0:08:28.280 came upon this very elegant solution to a lot of 0:08:28.320 --> 0:08:31.320 problems that a bridge poses. Because, as you were saying, 0:08:31.720 --> 0:08:34.520 when when you come upon like a river or creek 0:08:34.600 --> 0:08:36.160 or something, you say, I'm on this side and I 0:08:36.200 --> 0:08:37.520 need to be on the other side, so I need 0:08:37.520 --> 0:08:41.360 something to walk across. Yeah, Okay, that's a basic solution. 0:08:41.400 --> 0:08:43.560 But the further and further you get, the more and 0:08:43.600 --> 0:08:49.600 more problems. Like as bridge billers say, most span more problems. Yeah, 0:08:49.600 --> 0:08:51.079 I guess what we should have said is I want 0:08:51.120 --> 0:08:54.800 to walk across and live. I want to walk all 0:08:54.840 --> 0:08:57.640 the way across, right, I don't want to fall down. No, 0:08:57.679 --> 0:08:59.680 I don't want to get halfway across and have it snapped. 0:09:00.080 --> 0:09:06.040 So over the years, as people have come upon problems 0:09:06.120 --> 0:09:08.800 where you are going to build a bridge that will 0:09:08.840 --> 0:09:12.080 snapping and kill you, they've come up with solutions to 0:09:12.360 --> 0:09:15.120 prevent that from happening. That's pretty much the pursuit of 0:09:15.200 --> 0:09:18.280 bridge building is coming up with ways to prevent a 0:09:18.320 --> 0:09:20.640 bridge from collapsing, and a lot of trial and error 0:09:20.640 --> 0:09:23.400 over the years, you know, and a lot of real 0:09:23.720 --> 0:09:27.960 significant disasters. In fact, there's a Time magazine slide show 0:09:28.760 --> 0:09:33.200 um called worst Bridge Collapses in Past one years, um, 0:09:33.280 --> 0:09:35.480 and it's got all these photos of collapse bridges and 0:09:35.520 --> 0:09:38.719 little descriptions and the number of fatalities and everything. But um, 0:09:38.720 --> 0:09:42.000 it's it's really interesting all these different bridges have collapsed 0:09:42.000 --> 0:09:44.680 and failed for all these different reasons. Well and after 0:09:44.760 --> 0:09:48.120 each one, uh it's very sad, of course, but after 0:09:48.160 --> 0:09:51.000 each one someone goes, oh, well we should do this 0:09:51.160 --> 0:09:54.800 for the next one. We should not forget that bolt 0:09:55.040 --> 0:09:57.400 next time. Well, that's that could be human Ara, True, 0:09:57.520 --> 0:10:02.000 that's happened. Yeah, I'm sure. All right. So should we 0:10:02.000 --> 0:10:07.200 start off with the bats? Be a t s. Beams, arches, trusses, 0:10:07.679 --> 0:10:13.160 and suspensions are the main components of the structural components 0:10:13.160 --> 0:10:16.679 of a bridge. It's very simple. That's it. That's all 0:10:16.720 --> 0:10:19.600 you need to know to construct your own bridge. And 0:10:19.679 --> 0:10:22.880 with these four things you can make almost any kind 0:10:22.880 --> 0:10:27.160 of bridge. Um, we're gonna cover mainly beam bridges, arch bridges, 0:10:27.600 --> 0:10:32.120 trust bridges, suspension bridges, and then the super cool looking 0:10:32.600 --> 0:10:36.559 cable stayed bridge. It is super cool looking, probably my 0:10:36.600 --> 0:10:39.480 favorite looking bridge in the world that I came across 0:10:39.520 --> 0:10:43.280 and reach researching. This is a cable stayed bridge, the 0:10:43.320 --> 0:10:45.960 one that's in the article. Oh yeah, they look like 0:10:46.880 --> 0:10:50.839 look like sales gorgeous, the big triangles rising up. It's lovely. 0:10:51.480 --> 0:10:53.280 But they look a little more modern to me. They 0:10:53.280 --> 0:10:57.600 don't have that classic architecture like the Brooklyn Bridge does, 0:10:57.720 --> 0:10:59.600 or like the Tower Bridge in London. Yeah, I think 0:10:59.640 --> 0:11:02.560 that's why I like it. Yeah you like the modern look. Yeah, yeah, 0:11:02.760 --> 0:11:07.920 you're a modern guy. I'm super mod alright. Um. They 0:11:07.960 --> 0:11:10.040 point out in the article, which is very key. What 0:11:10.120 --> 0:11:13.520 you talked about. The span of the bridge is the 0:11:13.559 --> 0:11:17.200 distance between the supports, and that's where Um, that's where 0:11:17.200 --> 0:11:20.120 it all goes down. Basically, Yes, that's got to be 0:11:20.160 --> 0:11:23.080 strong there. Those are something that every single bridge has 0:11:23.200 --> 0:11:26.319 is a span and at least one support most likely 0:11:26.400 --> 0:11:33.079 to yeah, you know, um, and there's different The reason 0:11:33.160 --> 0:11:36.800 that there are different types of bridges because different bridge 0:11:36.840 --> 0:11:42.160 designs that that bats designs what is it, beams, arches, trusses, 0:11:42.160 --> 0:11:47.920 and suspension. They provide stability for varying span lengths. So 0:11:48.040 --> 0:11:50.319 like a beam, if you have like a fifty ft 0:11:50.840 --> 0:11:55.760 UM span, just put a like a very long log 0:11:55.840 --> 0:11:59.040 over over the span and there you go. There's your bridge. 0:11:59.440 --> 0:12:01.800 But as you get further and further along, you have 0:12:01.880 --> 0:12:04.480 more and more problems supporting that span, So you need 0:12:04.559 --> 0:12:07.840 different types of solutions, and the different length of the 0:12:07.880 --> 0:12:12.040 span calls usually for a specific type of bridge design. Yeah, 0:12:12.120 --> 0:12:14.640 and generally it'll I mean there's a lot of overlap, 0:12:14.640 --> 0:12:17.800 of course, but UM beam bridges tend to be the shortest, 0:12:18.040 --> 0:12:21.240 followed by arch bridges and then suspension bridges, and I 0:12:21.240 --> 0:12:25.559 think those UM the cable stayed bridge is is kind 0:12:25.559 --> 0:12:28.080 of a suspension bridge, so that counts. It's like a 0:12:28.160 --> 0:12:32.440 kind of a variation that can be very long as well. Yeah, 0:12:32.559 --> 0:12:34.920 not quite as long as suspension bridges, though from what 0:12:35.000 --> 0:12:38.320 I understand and this um, the suspension bridge affords the 0:12:38.400 --> 0:12:41.360 longest span. Okay, so you've got a big long span, 0:12:42.360 --> 0:12:46.480 it's it's suspension time. And they're also super expensive. Yeah, 0:12:46.520 --> 0:12:49.679 suspension bridges because all the bridge builders know that you've 0:12:49.679 --> 0:12:51.480 got a long span that you're trying to cross, you 0:12:51.559 --> 0:12:53.720 probably got some deep pockets and they're gonna milk you 0:12:53.760 --> 0:12:57.200 for it. Oh yeah, every penny. Yeah yeah, Like you 0:12:57.240 --> 0:13:00.840 need a suspension bridge, I'm your guy. Yep. Um. All right, 0:13:00.920 --> 0:13:03.480 so let's talk about there are a lot of different 0:13:03.840 --> 0:13:06.760 forces that can act on a bridge to make it 0:13:06.840 --> 0:13:10.040 not as stable. UM will cover a few of the 0:13:10.920 --> 0:13:14.079 other ones later, but the main two here early on 0:13:14.240 --> 0:13:18.160 our tension and compression. And the very easy way to 0:13:18.200 --> 0:13:21.120 think about these two things is tension is like if 0:13:21.160 --> 0:13:23.000 you if you and I are pulling a rope, like 0:13:23.080 --> 0:13:24.839 you're on one end and I'm on the other, We're 0:13:24.840 --> 0:13:28.199 gonna pull that sucker tight and I'm gonna fall over 0:13:28.400 --> 0:13:33.000 due to your massive strength. I'm pretty huge, But there 0:13:33.000 --> 0:13:37.640 will be some tension in that rope. Yeah, is f 0:13:37.760 --> 0:13:40.679 do you fall down? Yeah, and I'd start laughing. There 0:13:40.679 --> 0:13:44.200 would be tension, sure, But tension is the lengthening of something. Yes, 0:13:44.400 --> 0:13:47.800 Compression is the shortening of something, Yeah, like a spring collapse. Right. 0:13:47.840 --> 0:13:50.280 So it's easy to visualize when you're talking like springs 0:13:50.280 --> 0:13:52.040 and ropes and that kind of thing. But if you're 0:13:52.040 --> 0:13:55.200 talking about just a single deck of a bridge, which 0:13:55.200 --> 0:13:58.600 you think of as one piece, Um, it's tough too. 0:13:58.960 --> 0:14:02.280 It starts to get tough to visualize it until you 0:14:02.360 --> 0:14:04.800 realize that you have to look at like a bridge 0:14:04.840 --> 0:14:08.960 deck like the roadway on the bridge, as really having 0:14:09.000 --> 0:14:12.480 a top and a bottom. Yes, and forces, Well, the 0:14:12.520 --> 0:14:15.760 compression acts in the downward motion on the top, and 0:14:15.880 --> 0:14:20.240 the tension acts from the underneath coming up on the bottom. Right, 0:14:20.280 --> 0:14:24.480 So the bottom of the bridge, underneath it of the 0:14:24.560 --> 0:14:28.440 deck is going to be spread out under the force 0:14:28.440 --> 0:14:32.560 of tension. We're on top where it's being pushed down compressed. 0:14:33.320 --> 0:14:36.960 That's compression. Yeah, And they kind of, in a weird way, 0:14:37.000 --> 0:14:40.520 work together. Even though they're sort of opposite things, they're 0:14:40.520 --> 0:14:45.520 definitely related. Uh, And what will happen is if these uh, 0:14:45.880 --> 0:14:49.680 if you aren't a very good bridge builder, um, buckling 0:14:49.680 --> 0:14:54.040 will occur when it's compressed on the top, and snapping 0:14:54.080 --> 0:14:58.200 can occur on the bottom when tension is at work. 0:14:58.480 --> 0:15:00.600 That's right, all sounds very can using. But if you 0:15:00.720 --> 0:15:03.080 just I gotta do is like put your hand out 0:15:03.120 --> 0:15:05.880 and look at it, right, you know, and so or 0:15:06.080 --> 0:15:08.400 if you take and push down on your hand or 0:15:08.640 --> 0:15:12.600 on your hand, right, you know what I'm saying like that, yeah, 0:15:12.720 --> 0:15:17.280 like that. Um, the whole thing becomes very very evident 0:15:17.520 --> 0:15:20.920 when you look at a beam bridge, right, the most 0:15:20.960 --> 0:15:23.280 basic form of a bridge, like if you dropped a 0:15:23.320 --> 0:15:26.320 log over a river, right, and this this thing. Um. 0:15:26.440 --> 0:15:29.000 This article used the example of like taking a pair 0:15:29.040 --> 0:15:31.920 of milk crates and putting like a two by four 0:15:31.920 --> 0:15:35.080 across them. Right, if you put like a bowling ball 0:15:36.200 --> 0:15:39.440 on a bowling ball stand so it doesn't roll around 0:15:39.520 --> 0:15:42.360 on top of the um on top of or right 0:15:42.360 --> 0:15:45.360 in the middle of your two by four, which makes 0:15:45.400 --> 0:15:49.480 up your beam bridge deck. Right, Um, you're gonna see 0:15:49.480 --> 0:15:51.840 that it bows. And what you're seeing is that on 0:15:51.880 --> 0:15:54.680 the top it's being compressed. On the bottom, it's being 0:15:54.880 --> 0:15:59.320 um tensed. Right. Um, And what you've just done is 0:15:59.360 --> 0:16:02.360 at a low to that bridge. And there's two kinds 0:16:02.400 --> 0:16:05.000 of loads to start out with. There's a deadload, which 0:16:05.040 --> 0:16:07.200 is the weight of the bridge and all of its 0:16:07.240 --> 0:16:11.000 materials combined. And then there's a live load, which is say, 0:16:11.080 --> 0:16:13.680 like the cars and the people and the trains and 0:16:13.720 --> 0:16:16.640 everything that that add the extra weight while they're moving 0:16:16.680 --> 0:16:19.480 across it and everything. And as you add this extra load, 0:16:19.560 --> 0:16:22.000 first of all, the bridge is already dealing with its deadload. 0:16:22.400 --> 0:16:24.600 It's got to hold that up. That's job number one 0:16:24.680 --> 0:16:26.680 for a bridge. Yeah, Like if you had a three 0:16:26.800 --> 0:16:29.640 hundred foot two by four and two milk crates is 0:16:29.640 --> 0:16:32.560 gonna sag in the middle just naturally, right, and it 0:16:32.640 --> 0:16:34.800 might even break. And there have been bridges that have 0:16:34.880 --> 0:16:37.400 been built that where the guy forgot to carry the 0:16:37.440 --> 0:16:40.280 one or whatever and they couldn't stand up under their 0:16:40.280 --> 0:16:42.600 own weight and they collapse from their own weight. They 0:16:42.640 --> 0:16:45.280 collapse from the deadload. So job number one of the 0:16:45.360 --> 0:16:48.720 bridge is to support its own weight. Job number one 0:16:48.880 --> 0:16:53.000 point one is to support all of the live load 0:16:53.120 --> 0:16:56.960 the traffic that goes across it as well. Uh. And 0:16:57.000 --> 0:16:59.440 the two ways that you're going to do this to counteract. 0:17:00.000 --> 0:17:05.280 Tension and compression are dissipation and transference force or transferring 0:17:05.320 --> 0:17:09.560 the force. So with dissipation you spread out that force equally, 0:17:09.600 --> 0:17:13.720 you spread out over a wide area, and with transferring um, 0:17:13.800 --> 0:17:17.560 you move the area of weakness to an area of strength, right, 0:17:17.600 --> 0:17:21.840 which pretty simple. Yeah, they're kind of tough to distinguish sometimes, Yeah, 0:17:22.080 --> 0:17:24.560 you know what I mean. But for example, like the 0:17:24.600 --> 0:17:28.040 best example of dissipation is the arch, which we'll talk 0:17:28.080 --> 0:17:31.000 about how that works in a second. Yea, um, but 0:17:31.240 --> 0:17:37.280 suspension bridges are best at transferring the um the tension 0:17:37.520 --> 0:17:41.200 and compression forces. That's right. So if you're if you're 0:17:41.200 --> 0:17:43.840 talking about a beam bridge, that most basic kind. Uh. 0:17:43.920 --> 0:17:45.600 The other thing they're gonna do to make it stronger, 0:17:45.640 --> 0:17:47.800 of course is use back in the old days to 0:17:47.880 --> 0:17:51.119 use wood than later iron and then steel, maybe some 0:17:51.200 --> 0:17:55.119 concrete mixed in um. But the size of the beam 0:17:55.400 --> 0:17:57.560 is going to be really important. Like the height of 0:17:57.600 --> 0:18:00.840 the beam is important because the the top is gonna 0:18:00.840 --> 0:18:03.399 experience stress, the bottom is gonna experience stress in the 0:18:03.440 --> 0:18:06.919 middle not as much. So a good I beam, a 0:18:06.920 --> 0:18:08.840 good tall I beam, is what you want. Yeah, and 0:18:08.880 --> 0:18:11.000 I didn't realize that that's why I beams are made 0:18:11.200 --> 0:18:15.919 like I beam, the center of like the deck or 0:18:15.960 --> 0:18:18.720 the beam or whatever. Any kind of beam is going 0:18:18.760 --> 0:18:22.000 to experience the least amount of compression or tension. It's 0:18:22.000 --> 0:18:24.560 really the top or the bottom. So you don't have 0:18:24.600 --> 0:18:26.960 to put quite as much material into the center of 0:18:27.000 --> 0:18:29.240 the beam as you do the top and the bottom 0:18:29.400 --> 0:18:33.359 to prevent buckling and snapping. That's right. So the beam bridge, 0:18:33.400 --> 0:18:36.359 you're gonna add what's called a truss uh to make 0:18:36.400 --> 0:18:38.960 it stronger. This we'll talk about trust is more but 0:18:39.400 --> 0:18:44.600 it's basically triangulated strength. And you'll see a trust if 0:18:44.600 --> 0:18:48.879 you've ever seen like a a train bridge, like you 0:18:48.920 --> 0:18:53.200 see a truss on top, or like in areas where 0:18:53.400 --> 0:18:56.760 they get a lot of snow, roof supports will frequently 0:18:56.800 --> 0:18:59.600 be trusses. Yeah, and that's a three trust on top 0:18:59.640 --> 0:19:02.480 we already said. And if it's underneath then it is 0:19:02.800 --> 0:19:06.919 uh the deck trust. And you can have both, but usually, 0:19:06.960 --> 0:19:09.879 like with the railroads, you'll see like that top trust 0:19:10.680 --> 0:19:14.200 not the same as a trestle. That's different. It's like 0:19:14.200 --> 0:19:17.960 like a roller coaster, you know. So after this break, 0:19:17.960 --> 0:19:43.159 why don't we talk more about trust bridges? Nice? So, Chuck, 0:19:43.280 --> 0:19:46.280 no joke, trusses are one of my favorite things. Now 0:19:46.560 --> 0:19:49.399 it's pretty neat. After doing some research into them, I'm like, 0:19:49.680 --> 0:19:53.560 I love trust is your trust guy? Yeah? And it's 0:19:53.600 --> 0:19:59.240 because they're so elegant and simple. They're elegantly simple basically. 0:19:59.760 --> 0:20:04.159 So um. I saw this really great explanation where it 0:20:04.280 --> 0:20:06.720 was on Make magazine, and I think it was called like, 0:20:06.800 --> 0:20:11.480 ask Make, how do trust his work? Pretty straightforward? Um, 0:20:11.520 --> 0:20:14.359 And it basically had like a really get a great 0:20:14.400 --> 0:20:20.199 graphic of taking using popsicle sticks. Right, Let's say you 0:20:20.240 --> 0:20:22.800 make a square out of popsicle sticks and you join 0:20:22.880 --> 0:20:25.840 the popsicle sticks together at the corners where the ends 0:20:25.880 --> 0:20:28.800 all meet. Yeah, a little Elmer's paste maybe makes sense, 0:20:29.400 --> 0:20:32.840 seems pretty supportive. Right, But when you pressed down on 0:20:33.160 --> 0:20:35.679 any one of those joints, which is where the load's 0:20:35.720 --> 0:20:41.320 going to be centered or distributed most remember the ends 0:20:41.600 --> 0:20:44.280 the square shift to the side, and all of a 0:20:44.280 --> 0:20:47.320 sudden you have a rhombus. Well, rambus is inherently less 0:20:47.320 --> 0:20:51.159 structurally sound than square, which is why you very rarely 0:20:51.200 --> 0:20:55.600 see rambus as in architecture. Right, with a triangle, when 0:20:55.600 --> 0:20:58.439 you press down at any one of the joints it 0:20:58.560 --> 0:21:03.479 distributes that can pression or tension directly through the center 0:21:04.119 --> 0:21:08.359 of the beam, so the triangle stays totally rigid. And 0:21:08.400 --> 0:21:10.520 when you add, the more triangles you add, the more 0:21:10.560 --> 0:21:14.440 support you have. So they're like basically like as far 0:21:14.480 --> 0:21:18.720 as the shape goes, the superconductor of transferring or distributing 0:21:19.560 --> 0:21:22.840 compression or tension. Yeah, that's a good way to put it. 0:21:22.880 --> 0:21:25.480 And that's why when you see that that train tress 0:21:25.560 --> 0:21:28.000 alone that has that trust on top, it's got all 0:21:28.000 --> 0:21:33.000 those beautiful diagonal uh pieces of metal and it's not 0:21:33.080 --> 0:21:35.320 just for for looks, even though it is cool looking. Now, 0:21:35.640 --> 0:21:38.439 one of the other great things about a trust is 0:21:38.480 --> 0:21:41.359 that there you know, it's like just a three steel 0:21:41.400 --> 0:21:45.320 beams or three whatever aluminum beams. They're just three pieces 0:21:45.320 --> 0:21:49.480 of metal, usually fixed together. And that's that's the other 0:21:49.560 --> 0:21:52.480 key that I left out. They have to be connected 0:21:52.520 --> 0:21:57.280 at the ends equally distributed from each end. Right, So 0:21:57.359 --> 0:21:59.840 let's say you you drill a hole to to rivet 0:22:00.040 --> 0:22:02.720 one side of the trust to another, or one end 0:22:02.760 --> 0:22:06.080 of the trust to another end, the the other end 0:22:06.119 --> 0:22:09.440 has to be equally far away, right. Do you see 0:22:09.440 --> 0:22:11.520 what I'm saying? Yeah, yeah, okay. They wouldn't just be 0:22:11.520 --> 0:22:14.119 like just droll that other one wherever. So anyway you 0:22:14.160 --> 0:22:18.520 have to the place where the trust sides join together 0:22:18.560 --> 0:22:21.000 has to be on the ends and then but one 0:22:21.000 --> 0:22:23.800 of the things that it allows for is for wind 0:22:23.840 --> 0:22:27.520 to blow through it easily. That's a huge point about trusses. 0:22:28.080 --> 0:22:33.080 They're not solid in that they don't they don't put 0:22:33.160 --> 0:22:35.240 up a lot of resistance to when they allow it 0:22:35.280 --> 0:22:37.320 to flow through, which is really kind of what you want. 0:22:37.440 --> 0:22:40.760 We'll see when you're building bridges. Yeah. I think even 0:22:40.800 --> 0:22:43.480 the covered bridges have is more of a lattice type 0:22:43.480 --> 0:22:47.560 thing on the sides. Right, Yes, it's not solid, is it. 0:22:47.600 --> 0:22:50.280 That'd be dumb a covered bridge. Yeah, yeah, they're solid. 0:22:50.720 --> 0:22:52.719 I thought the walls were usually like a lattice so 0:22:52.800 --> 0:22:55.280 wind could pass through. Now and they had that had 0:22:55.280 --> 0:23:00.280 a roof and like a lattice e side is the right. Yeah, 0:23:00.359 --> 0:23:04.000 maybe there's all kinds. I think those are just to 0:23:04.080 --> 0:23:07.840 keep the rain off. Oh yeah, that's what you said 0:23:07.840 --> 0:23:13.240 earlier and keep shooting down the theoris structure. Yeah. But anyway, 0:23:13.280 --> 0:23:16.119 trust is rock, I guess, is what I'm trying to say. Yes, 0:23:16.440 --> 0:23:20.199 there's your T shirt. Trust is rock. So are we 0:23:20.240 --> 0:23:24.480 at arches? Do we say that they frequently used trusses 0:23:24.560 --> 0:23:30.760 to support beam bridges. Yeah, arches. Now, when we say 0:23:30.800 --> 0:23:33.679 a bridge is an arch bridge, the deck is not 0:23:34.520 --> 0:23:38.080 some big hill that you drive over. The deck is 0:23:38.080 --> 0:23:43.959 flat the arches underneath. Uh right, yeah. And you can 0:23:44.000 --> 0:23:46.640 have a single arch if your span isn't it long, 0:23:46.720 --> 0:23:49.000 or you can have a big one with like six 0:23:49.080 --> 0:23:52.280 or eight arches. Although I've seen I think there are 0:23:52.359 --> 0:23:55.760 like short arch bridges that actually do go up and down, 0:23:56.560 --> 0:23:59.040 you know, like if I mean there's natural arch bridges 0:23:59.240 --> 0:24:01.200 like rock form a sans like that, and that's why 0:24:01.200 --> 0:24:05.400 they're still standing. There's um there's there's a bridge that 0:24:06.520 --> 0:24:10.439