WEBVTT - Bridges: Nature Abhors Them 0:00:01.040 --> 0:00:04.200 Welcome to you Stuff you Should Know from House Stuff 0:00:04.240 --> 0:00:12.520 Works dot com. Hey, and welcome to the podcast. I'm 0:00:12.600 --> 0:00:15.760 Josh Clark with Charles W. Chuck Bryant with Jerry Rowland 0:00:16.280 --> 0:00:19.479 with me Josh Clark, Mr. Stuff you Should Know featuring 0:00:19.600 --> 0:00:22.759 Josh Clark's about to say you never introduced yourself and 0:00:22.800 --> 0:00:27.200 then you done did it twice three three times? Oh yeah, 0:00:27.280 --> 0:00:30.120 you always introduce your but you never say your last name. 0:00:30.160 --> 0:00:34.680 I think that's extruct me. John. No, I say I'm 0:00:34.760 --> 0:00:37.320 Josh Clark, do you Yeah? Every time I should listen 0:00:37.360 --> 0:00:41.519 to the Sometimes that explains the glazed overlook in your 0:00:41.560 --> 0:00:49.599 eyes whenever we start um bridges. Yeah, is that your intro? Ye? 0:00:50.760 --> 0:00:53.120 I like them. Maybe we can add like a scat 0:00:53.200 --> 0:00:56.640 drummer on top of that. We have that kind of 0:00:56.760 --> 0:00:59.720 um when we're doing uh listener mail, there's a little 0:00:59.720 --> 0:01:02.800 bit of oh yeah, well that's not scat drumming. I 0:01:02.800 --> 0:01:05.880 would say that's more of a shuffle mhm scots like 0:01:07.800 --> 0:01:10.040 yeah like that. Yeah, you should get Hodgment to scat 0:01:10.040 --> 0:01:14.520 for you sometime. He's got a lot of boot boot 0:01:14.520 --> 0:01:20.000 bidus going on when he's scatting any jazz hands. No, No, 0:01:20.040 --> 0:01:27.959 it's not exactly Manhattan Transfer level. He's intermediate. Yeah uh 0:01:28.040 --> 0:01:32.160 yeah so again, Princess. Yeah, you know, I bet we're 0:01:32.200 --> 0:01:35.760 gonna hear from some folks because there are bridge enthusiasts, 0:01:36.720 --> 0:01:38.959 which I think is kind of neat. Yeah. Well, I 0:01:38.959 --> 0:01:42.680 mean they're like modern marvels of engineering, and actually there's 0:01:42.720 --> 0:01:47.120 some ancient marvels of engineering too, as far as they are. 0:01:47.280 --> 0:01:52.120 Um yeah, there you Basically I was talking to our 0:01:52.200 --> 0:01:58.680 pal um Adam the architect o, the bridge builder. No, yeah, uh, 0:01:58.680 --> 0:02:02.520 he's a building builder. We're a building designer. I don't 0:02:02.520 --> 0:02:04.440 know if he actually knows how to build the buildings. 0:02:04.480 --> 0:02:06.120 He just knows how to tell other people how to 0:02:06.160 --> 0:02:10.280 build that. Adam can't swing a hammer. He was saying that, 0:02:10.440 --> 0:02:17.720 um uh the um. Basically, the structural engineers who designed 0:02:17.720 --> 0:02:21.480 bridges are just straight up geniuses. Like it requires a 0:02:21.600 --> 0:02:25.040 basically a genius to factor in all of this stuff. Yeah, 0:02:25.040 --> 0:02:28.600 anyone can design a building, you know, there's just four 0:02:28.639 --> 0:02:31.200 walls and a bunch of floors. Put a roof on it. 0:02:31.600 --> 0:02:36.880 Bridge though it's different. Yes, right, there aren't walls really, Um, 0:02:37.040 --> 0:02:39.360 there can be bridges of Madison County they had walls. 0:02:39.440 --> 0:02:41.920 Oh yeah, they have walls. I was going to mention 0:02:41.960 --> 0:02:44.600 the bridges of Madison County. Yeah, I love those that 0:02:44.600 --> 0:02:49.520 that'd be a beam bridge, I guess, yeah, with a trust, right, 0:02:50.120 --> 0:02:53.960 the top trust was the top trust film a through 0:02:54.000 --> 0:02:58.160 trust through trusts, and then below that. If they were 0:02:58.200 --> 0:03:00.280 below it would be a deck trust. But don't know 0:03:00.280 --> 0:03:01.760 if that counts as a trust. It's more just like 0:03:01.800 --> 0:03:04.120 a house on top of the bridge. I bet their 0:03:04.160 --> 0:03:07.560 structural support there. May thought it was mainly just to 0:03:07.639 --> 0:03:09.639 keep the rain off of you when you crossed the bridge, 0:03:09.639 --> 0:03:12.720 like just an extra little thank you for crossing the bridge. 0:03:12.760 --> 0:03:15.120 I thought it was just to draw in Lackey tourists 0:03:15.639 --> 0:03:19.640 who wanted to have their picture made. Another famous bridge, 0:03:20.040 --> 0:03:22.880 the one that the Headless Horseman couldn't cross in the 0:03:23.000 --> 0:03:27.040 legend of Sleepy Hallow. Oh yeah, wouldn't that a bridge? Sure? 0:03:27.320 --> 0:03:31.120 Trolls of under bridges that draw bridges are pretty cool. 0:03:31.639 --> 0:03:35.360 Have you ever seen Maximum Overdrive? The beginning of that movie? Um, 0:03:35.400 --> 0:03:38.240 it's been many, many years. I saw it again. I 0:03:38.280 --> 0:03:41.240 saw it again very recently, like this year, and it 0:03:40.480 --> 0:03:43.480 is it's maybe better than it was before. It holds 0:03:43.560 --> 0:03:47.480 up as a crappy movie. Still. Yeah, the whole soundtrack 0:03:47.560 --> 0:03:49.160 is a C D C by the way, which you 0:03:49.200 --> 0:03:52.240 should love the whole sound I do love that, and 0:03:52.280 --> 0:03:55.080 I do remember that. And didn't Stephen King direct that, 0:03:56.120 --> 0:03:58.840 which he doesn't do much, right, No, but maybe it's 0:03:58.840 --> 0:04:01.720 the only one is definitely far interesting. But there's a 0:04:01.720 --> 0:04:06.720 great draw draw bridge scene in there. Uh did someone 0:04:06.800 --> 0:04:11.480 jump it jump the span as it raised? No? I 0:04:11.520 --> 0:04:14.280 think their car fell into their truck felling. Okay, because 0:04:14.360 --> 0:04:17.080 usually the drawbridge scene is like I can make it. 0:04:18.560 --> 0:04:24.520 Uh No, this one was you're all doomed and uh, 0:04:24.600 --> 0:04:27.919 let me also recommend Budapest for bridges. You mean I 0:04:27.960 --> 0:04:30.240 went to Budapest a couple of New years as ago. Yeah, 0:04:30.279 --> 0:04:32.919 I went there like twenty years ago. Okay, so yeah, 0:04:33.120 --> 0:04:35.720 you know the bridges are amazing that I think like 0:04:35.839 --> 0:04:40.680 five because they connect the two sides, yeah, Buddha and Pest, right, 0:04:41.000 --> 0:04:43.880 and each one is totally different, like it's just a 0:04:43.920 --> 0:04:48.760 completely different design. Yeah, and they're just all gorgeous. Yeah, 0:04:48.960 --> 0:04:51.120 let's just start with a bunch of bridge recommendations. I'm 0:04:51.160 --> 0:04:56.280 going to recommend the City of Pittsburgh baseball game there, 0:04:56.320 --> 0:04:59.359 and it's just just gorgeous. Those beautiful bridges that you 0:04:59.400 --> 0:05:02.320 can see from the baseball stadium and the river. That 0:05:02.400 --> 0:05:07.080 was when we were a Toyota commercial ring. Right. Yeah, 0:05:07.120 --> 0:05:11.159 I stayed in the hotel and just eight um sog 0:05:11.200 --> 0:05:14.440 copenny r no chicken sog. Right, it's just like a 0:05:14.600 --> 0:05:17.160 quarter of it. But you can see the baseball stadium 0:05:17.160 --> 0:05:20.359 out your hotel window. Yeah. And I saw some bridges 0:05:20.400 --> 0:05:22.520 to Yeah, you walk across the bridge to get there. 0:05:22.920 --> 0:05:27.960 Really swe did what else any other bridges, well, Brooklyn Bridge, 0:05:28.880 --> 0:05:31.520 Golden Gate Bridge, this are like the famous ones. They're 0:05:31.560 --> 0:05:34.920 barely even worth mentioning. Yeah, but the Brooklyn Bridge is 0:05:35.760 --> 0:05:38.679 for your money. It's which is free. It's a pretty 0:05:38.720 --> 0:05:41.080 great thing to do to walk across it. It's it's 0:05:41.240 --> 0:05:43.920 just beautiful. I've never done that. You should do it. 0:05:44.080 --> 0:05:47.360 Even the Geico Lizard did it, and I haven't. That 0:05:47.440 --> 0:05:49.800 guy's like Australian or something. Well, maybe we should just 0:05:49.839 --> 0:05:52.680 animate you and have you walk across it. Uh. One 0:05:52.680 --> 0:05:55.640 more thing if you want to know more about the 0:05:55.640 --> 0:05:58.440 Brooklyn Bridge, I don't remember which one we talked about it, 0:05:58.480 --> 0:06:01.640 and but there is a really cool documentary about the 0:06:01.680 --> 0:06:06.279 Brooklyn Bridge and it's building by Ken Burns. Oh wow, 0:06:06.400 --> 0:06:08.719 I believe it's on Netflix. I'll have to check that 0:06:08.760 --> 0:06:13.320 out then, yep, because I like cain Burns and Brooklyn bridges, 0:06:14.480 --> 0:06:19.839 all right, you ready? Uh yeah, man, So bridges have 0:06:19.920 --> 0:06:22.640 been around for a very long time. This article is 0:06:22.680 --> 0:06:26.080 by Robert Lam and another dude named Michael Morrissey together. 0:06:26.520 --> 0:06:29.560 I believe they were locked away in a closet for 0:06:29.640 --> 0:06:33.160 like a couple of months while they worked this out together. Well, 0:06:33.320 --> 0:06:35.200 he the one of the first ones that talking about 0:06:35.200 --> 0:06:40.320 ancient bridges that they mentioned in here, the Arcadeco Bridge 0:06:40.600 --> 0:06:44.240 in ancient Greece. Did you see that thing? It's really neat. 0:06:44.279 --> 0:06:47.200 I mean it still stands. It's a three thousand year 0:06:47.200 --> 0:06:50.680 old bridge, and uh, it's just kind of cool to 0:06:50.720 --> 0:06:55.640 think about, you know, ancient civilizations and ancient times. People said, 0:06:55.680 --> 0:06:58.880 well I want to get over there, and I'm here, 0:06:59.760 --> 0:07:02.240 and so let's build something to do that. I need 0:07:02.279 --> 0:07:05.760 something to walk on or drive my card over that. 0:07:05.839 --> 0:07:09.040 Si Um, I just saw that. I saw the world's 0:07:09.080 --> 0:07:13.280 oldest bridge that's still in use. Um is in Turkey 0:07:13.320 --> 0:07:20.160 over the Mulis River, I believe from eight Do you 0:07:20.200 --> 0:07:23.360 know what that's how it's constructed. It is a single 0:07:23.520 --> 0:07:28.520 It is a single stone slab. Archy. No, it is 0:07:28.560 --> 0:07:32.480 a stone slab, single arch. Yeah that makes sense. Yeah, 0:07:33.280 --> 0:07:39.600 very basic. Yeah, but the arch it's super old. But 0:07:39.720 --> 0:07:43.880 it's still in use today because whoever figured it out 0:07:44.080 --> 0:07:46.680 came upon this very elegant solution to a lot of 0:07:46.720 --> 0:07:49.720 problems that a bridge poses. Because, as you were saying, 0:07:50.120 --> 0:07:52.880 when when you come upon like a river or creek 0:07:52.960 --> 0:07:54.560 or something, you say, I'm on this side and I 0:07:54.600 --> 0:07:55.880 need to be on the other side, so I need 0:07:55.920 --> 0:07:59.720 something to walk across. Yeah, okay, that's a basic solution. 0:07:59.760 --> 0:08:01.960 But the further and further you get, the more and 0:08:02.000 --> 0:08:07.960 more problems. Like, as bridge builders say, most span more problems. Yeah, 0:08:08.000 --> 0:08:09.480 I guess what we should have said is I want 0:08:09.480 --> 0:08:13.200 to walk across and live. I want to walk all 0:08:13.240 --> 0:08:16.000 the way across, right, I don't want to fall down. No, 0:08:16.080 --> 0:08:18.000 I don't want to get halfway across and have it snapped. 0:08:18.400 --> 0:08:24.440 So over the years, as people have come upon problems 0:08:24.520 --> 0:08:27.160 where you are going to build a bridge that will 0:08:27.240 --> 0:08:30.480 snapping and kill you, they've come up with solutions to 0:08:30.720 --> 0:08:33.520 prevent that from happening. That's pretty much the pursuit of 0:08:33.600 --> 0:08:36.680 bridge building is coming up with ways to prevent a 0:08:36.720 --> 0:08:39.040 bridge from collapsing, and a lot of trial and error 0:08:39.040 --> 0:08:41.800 over the years, you know, and a lot of real 0:08:42.120 --> 0:08:46.400 significant disasters. In fact, there's a Time magazine slide show 0:08:47.160 --> 0:08:51.600 um called worst Bridge Collapses in Past one years, um, 0:08:51.640 --> 0:08:53.839 and it's got all these photos of collapse bridges and 0:08:53.920 --> 0:08:57.120 little descriptions and the number of fatalities and everything. But um, 0:08:57.120 --> 0:09:00.400 it's it's really interesting all these different bridges of lapsed 0:09:00.400 --> 0:09:03.080 and failed for all these different reasons. Well and after 0:09:03.160 --> 0:09:06.480 each one, uh, it's very sad, of course, but after 0:09:06.559 --> 0:09:09.400 each one someone goes, oh, well we should do this 0:09:09.559 --> 0:09:13.200 for the next one. We should not forget that bolt 0:09:13.440 --> 0:09:15.800 next time. Well, that's that could be human Ara, True, 0:09:15.880 --> 0:09:20.360 that's happened. Yeah, I'm sure. All right. So should we 0:09:20.400 --> 0:09:25.600 start off with the bats be A t s. Beams, arches, trusses, 0:09:26.080 --> 0:09:31.560 and suspensions are the main components of the structural components 0:09:31.559 --> 0:09:35.080 of a bridge. It's very simple, that's it. That's all 0:09:35.120 --> 0:09:38.000 you need to know to construct your own bridge. And 0:09:38.080 --> 0:09:41.240 with these four things you can make almost any kind 0:09:41.280 --> 0:09:45.560 of bridge. Um. We're gonna cover mainly beam bridges, arch bridges, 0:09:46.000 --> 0:09:50.520 trust bridges, suspension bridges, and then the super cool looking 0:09:51.000 --> 0:09:55.360 cable stayed bridge. It is super cool, probably my favorite 0:09:55.360 --> 0:09:58.000 looking bridge in the world that I came across and 0:09:58.040 --> 0:10:01.840 reach researching. This is a cable stayed bridge, the one 0:10:01.880 --> 0:10:05.440 that's in the article. Oh yeah, they look like look 0:10:05.520 --> 0:10:09.240 like sales gorgeous, the big triangles rising up. It's lovely. 0:10:09.880 --> 0:10:11.679 But they look a little more modern to me. They 0:10:11.679 --> 0:10:16.000 don't have that classic architecture like the Brooklyn Bridge does, 0:10:16.120 --> 0:10:18.079 or like the Tower Bridge in London. Yeah. I think 0:10:18.080 --> 0:10:21.000 that's why I like it. Yeah, you like the modern look. Yeah, yeah, 0:10:21.160 --> 0:10:26.319 you're a modern guy. I'm super mod alright. Um. They 0:10:26.360 --> 0:10:28.400 point out in the article, which is very key. What 0:10:28.480 --> 0:10:31.880 you talked about. The span of the bridge is the 0:10:31.920 --> 0:10:35.600 distance between the supports, and that's where um, that's where 0:10:35.600 --> 0:10:38.839 it all goes down. Basically, Yes, that's got to be strong, 0:10:38.920 --> 0:10:41.480 there be those are something that every single bridge has 0:10:41.600 --> 0:10:44.679 is a span and at least one support most likely 0:10:44.760 --> 0:10:51.440 to Yeah you know, um, and there's different The reason 0:10:51.559 --> 0:10:55.200 that there are different types of bridges because different bridge 0:10:55.240 --> 0:11:00.560 designs that that bats designs what is it, beams, arches, trusses, 0:11:00.559 --> 0:11:06.320 and suspension. They provide stability for varying span lengths. So 0:11:06.400 --> 0:11:08.720 like a beam, if you have like a fifty ft 0:11:09.240 --> 0:11:13.760 um span, just put a a like a very long 0:11:13.800 --> 0:11:16.880 log over over the span and there you go, there's 0:11:16.880 --> 0:11:19.559 your bridge. But as you get further and further along, 0:11:19.920 --> 0:11:22.520 you have more and more problems supporting that span, so 0:11:22.600 --> 0:11:26.040 you need different types of solutions, and the different length 0:11:26.040 --> 0:11:29.000 of the span calls usually for a specific type of 0:11:29.040 --> 0:11:32.280 bridge design. Yeah, and generally it it'll I mean there's 0:11:32.280 --> 0:11:35.200 a lot of overlap, of course, but UM beam bridges 0:11:35.240 --> 0:11:37.680 tend to be the shortest, followed by arch bridges and 0:11:37.720 --> 0:11:42.720 then suspension bridges, and I think those UM the cable 0:11:42.720 --> 0:11:45.040 stayed bridge is is kind of a suspension bridge, so 0:11:45.080 --> 0:11:48.120 that counts. It's like a kind of a variation that 0:11:48.920 --> 0:11:51.480 can be very long as well. Yeah, not quite as 0:11:51.520 --> 0:11:54.160 long as suspension bridges though from what I understand, and 0:11:54.280 --> 0:11:58.080 this UM, the suspension bridge affords the longest span. Okay, 0:11:58.240 --> 0:12:02.440 so you've got a big long span, it's it's suspension time. Yeah. 0:12:02.480 --> 0:12:06.560 And they're also super expensive. Yeah, suspension bridges because all 0:12:06.640 --> 0:12:08.880 the bridge builders know that you've got a log span 0:12:09.000 --> 0:12:10.800 that you're trying to cross, you probably got some deep 0:12:10.800 --> 0:12:12.880 pockets and they're gonna milk you for it. Oh yeah, 0:12:12.920 --> 0:12:16.680 every penny. Yeah. Yeah, Like you need a suspension bridge 0:12:16.760 --> 0:12:20.280 I'm your guy. Um, all right, so let's talk about 0:12:20.679 --> 0:12:23.240 there are a lot of different forces that can act 0:12:23.280 --> 0:12:26.520 on a bridge to make it not as stable. Um. 0:12:26.960 --> 0:12:30.280 Will cover a few of the other ones later, but 0:12:30.320 --> 0:12:34.520 the main two here early on our tension and compression. 0:12:35.440 --> 0:12:37.360 And the very easy way to think about these two 0:12:37.440 --> 0:12:40.160 things is tension is like if you if you and 0:12:40.200 --> 0:12:42.040 I are pulling a rope, like you're on one end 0:12:42.080 --> 0:12:44.360 and I'm on the other, We're gonna pull that sucker tight, 0:12:45.120 --> 0:12:48.959 and uh, I'm gonna fall over due to your massive strength. 0:12:49.200 --> 0:12:52.160 I'm pretty huge, but um, there will be some tension 0:12:52.160 --> 0:12:57.320 in that rope. Yeah, f do you fall down? Yeah? 0:12:57.400 --> 0:13:00.000 And I'd start laughing if there would be tension. Sure. 0:13:00.160 --> 0:13:03.600 The tension is the lengthening of something. Compression is the 0:13:03.640 --> 0:13:06.360 shortening of something, Yeah, like a spring collapse. Right. So 0:13:06.400 --> 0:13:08.800 it's easy to visualize when you're talking like springs and 0:13:08.880 --> 0:13:10.640 ropes and that kind of thing. But if you're talking 0:13:10.679 --> 0:13:13.680 about just a single deck of a bridge, which you 0:13:13.720 --> 0:13:17.160 think of as one piece, Um, it's tough to it 0:13:17.480 --> 0:13:21.280 starts to get tough to visualize it until you realize 0:13:21.320 --> 0:13:23.480 that you have to look at like a bridge deck 0:13:23.800 --> 0:13:27.480 like the roadway on the bridge as really having a 0:13:27.559 --> 0:13:31.480 top and a bottom. Yes, and forces, Well, the compression 0:13:31.559 --> 0:13:34.439 acts in the downward motion on the top, and the 0:13:34.480 --> 0:13:38.640 tension acts from the underneath coming up on the bottom. Right, 0:13:38.679 --> 0:13:42.880 So the bottom of the bridge, underneath it, of the 0:13:42.960 --> 0:13:46.839 deck is going to be spread out under the force 0:13:46.840 --> 0:13:50.960 of tension. We're on top where it's being pushed down compressed. 0:13:51.679 --> 0:13:55.360 That's compression. Yeah, and they kind of in a weird way, 0:13:55.400 --> 0:13:58.880 work together. Even though they're sort of opposite things, they're 0:13:58.920 --> 0:14:02.840 definitely related, right. Uh. And what will happen is if 0:14:02.880 --> 0:14:07.520 these uh, if you aren't a very good bridge builder, um, 0:14:07.640 --> 0:14:11.559 buckling will occur when it's compressed on the top, and 0:14:11.920 --> 0:14:16.560 snapping can occur on the bottom when tension is at work. 0:14:16.880 --> 0:14:19.000 That's right. It all sounds very confusing, but if you 0:14:19.120 --> 0:14:21.480 just I gotta do is like put your hand out 0:14:21.520 --> 0:14:24.640 and look at it, you know, and so or if 0:14:24.680 --> 0:14:27.120 you take and push down on your hand or on 0:14:27.160 --> 0:14:31.000 your hand, right, you know what I'm saying, like that, yeah, 0:14:31.120 --> 0:14:35.680 like that. Um, the whole thing becomes very very evident 0:14:35.920 --> 0:14:39.320 when you look at a beam bridge, right, the most 0:14:39.360 --> 0:14:41.680 basic form of a bridge, like if you dropped a 0:14:41.680 --> 0:14:44.720 log over a river, right, and this this thing. Um. 0:14:44.840 --> 0:14:47.400 This article used the example of like taking a pair 0:14:47.400 --> 0:14:50.280 of milk crates and putting like a two by four 0:14:50.320 --> 0:14:53.480 across them. Right, if you put like a bowling ball 0:14:54.600 --> 0:14:57.200 on a bowling ball stand so it doesn't roll around, Yeah, 0:14:57.200 --> 0:15:00.840 that'd awkward on top of them, on top, right in 0:15:00.840 --> 0:15:03.920 the middle of your two by four, which makes up 0:15:03.960 --> 0:15:07.960 your beam bridge deck. Right, Um, you're gonna see that 0:15:08.000 --> 0:15:10.360 it bows, and what you're seeing is that on the 0:15:10.400 --> 0:15:16.080 top it's being compressed. On the bottom, it's being um tensed, right. Um. 0:15:16.200 --> 0:15:18.720 And what you've just done is add a load to 0:15:19.360 --> 0:15:21.520 that bridge. And there's two kinds of loads to start 0:15:21.520 --> 0:15:24.480 out with. There's a deadload, which is the weight of 0:15:24.560 --> 0:15:27.800 the bridge and all of its materials combined. And then 0:15:27.800 --> 0:15:30.600 there's a live load, which is say, like the cars 0:15:30.640 --> 0:15:32.960 and the people and the trains and everything that that 0:15:33.120 --> 0:15:36.080 add the extra weight while they're moving across it and everything. 0:15:36.320 --> 0:15:38.320 And as you add this extra load, first of all, 0:15:38.400 --> 0:15:41.160 the bridge is already dealing with its deadload. You's got 0:15:41.160 --> 0:15:44.080 to hold that up. That's job number one for a bridge. Yeah, 0:15:44.120 --> 0:15:46.760 Like if you had a three hundred foot two by 0:15:46.760 --> 0:15:49.280 four and two milk crates it's gonna sag in the 0:15:49.280 --> 0:15:51.920 middle just naturally, right, and it might even break. And 0:15:51.960 --> 0:15:54.520 there have been bridges that have been built that where 0:15:54.600 --> 0:15:57.080 the guy forgot to carry the one or whatever and 0:15:57.120 --> 0:15:59.480 they couldn't stand up under their own weight and they 0:15:59.520 --> 0:16:02.160 collapse from their own weight. They collapse from the deadload. 0:16:02.520 --> 0:16:04.840 So job number one of the bridge is to support 0:16:04.880 --> 0:16:09.040 its own weight. Job number one point one is to 0:16:09.800 --> 0:16:13.040 support all of the liveload the traffic that goes across 0:16:13.080 --> 0:16:16.000 it as well. That's right. Uh. And the two ways 0:16:16.080 --> 0:16:18.720 that you're going to do this to counteract tension and 0:16:18.720 --> 0:16:24.040 compression are dissipation and transference force or transferring the force. 0:16:24.120 --> 0:16:28.080 So with dissipation you spread out that force equally, you 0:16:28.120 --> 0:16:32.120 spread out over a wide area, and with transferring um 0:16:32.200 --> 0:16:35.960 you move the area of weakness to an area of strength, right, 0:16:36.000 --> 0:16:40.120 which pretty simple. Yeah, they're kind of tough to distinguish sometimes, Yeah, 0:16:40.440 --> 0:16:42.920 you know what I mean. But for example, like the 0:16:42.960 --> 0:16:46.440 best example of dissipation is the arch, which we'll talk 0:16:46.480 --> 0:16:50.240 about how that works in a second. Um. But suspension 0:16:50.280 --> 0:16:56.040 bridges are best at transferring the um the tension and 0:16:56.280 --> 0:16:59.760 compression forces. That's right. So if you're if you're talking 0:16:59.760 --> 0:17:02.400 about to beam bridge that most basic kind. Uh. The 0:17:02.400 --> 0:17:04.399 other thing they're gonna do to make it stronger, of course, 0:17:04.480 --> 0:17:06.840 is use back in the old days, use wood than 0:17:06.920 --> 0:17:12.159 later iron and then steel, maybe some concrete mixed in um. 0:17:12.200 --> 0:17:15.240 But the size of the beam is gonna be really important. 0:17:15.280 --> 0:17:18.480 Like the height of the beam is important because the 0:17:18.480 --> 0:17:20.840 the top is gonna experience stress, the bottom is gonna 0:17:20.840 --> 0:17:23.760 experience stress in the middle not as much. So a 0:17:23.800 --> 0:17:27.160 good I beam, a good tall ibam is what you want. Yeah, 0:17:27.200 --> 0:17:29.400 and I didn't realize that. That's why I beams are made. 0:17:29.600 --> 0:17:34.479 Like I beam, the center of the deck or the 0:17:34.520 --> 0:17:37.320 beam or whatever, any kind of beam is going to 0:17:37.359 --> 0:17:40.560 experience the least amount of compression or tension. It's really 0:17:40.640 --> 0:17:43.040 the top or the bottom. So you don't have to 0:17:43.080 --> 0:17:45.439 put quite as much material into the center of the 0:17:45.480 --> 0:17:47.879 beam as you do the top and the bottom to 0:17:48.040 --> 0:17:51.760 prevent buckling and snapping. That's right. So with the beam bridge, 0:17:51.800 --> 0:17:54.760 you're gonna add what's called a truss uh to make 0:17:54.800 --> 0:17:57.240 it stronger. This uh, we'll talk about trust is more 0:17:57.280 --> 0:18:02.840 but it's basically reriangulated strength. And you'll see a trust 0:18:02.880 --> 0:18:06.960 if you've ever seen like a a train bridge like 0:18:07.240 --> 0:18:11.320 you see a trust on top or like in areas 0:18:11.320 --> 0:18:14.560 where they get a lot of snow, roof supports will 0:18:14.640 --> 0:18:17.800 frequently be trusses. Yeah, and that's a three trust on 0:18:17.800 --> 0:18:20.639 top we already said. And if it's underneath then it 0:18:20.800 --> 0:18:24.720 is uh the deck trust and you can have both, 0:18:24.760 --> 0:18:27.600 but usually, like with the railroads, you'll see like that 0:18:27.680 --> 0:18:30.879 top trust not the same as a trestle. That's different. 0:18:31.560 --> 0:18:36.040 That's like like a roller coaster, you know. So after 0:18:36.040 --> 0:18:59.520 this break, why don't we talk more about trust bridges? Nice? So, 0:19:00.280 --> 0:19:03.320 no joke. Trusses are one of my favorite things now, 0:19:03.600 --> 0:19:06.399 it's pretty neat. After doing some research into him, I'm like, 0:19:06.640 --> 0:19:13.680 I love trust. Yeah, and it's because they're so elegant 0:19:13.760 --> 0:19:17.880 and simple. They're elegantly simple basically. So, um, I saw 0:19:17.960 --> 0:19:22.480 this really great explanation where it was on Make magazine 0:19:22.600 --> 0:19:25.320 and I think it was called like ask Make, how 0:19:25.359 --> 0:19:29.360 do trust? His work? Pretty straightforward, um, and it basically 0:19:29.400 --> 0:19:34.080 had like a really get a great graphic of taking 0:19:34.640 --> 0:19:37.879 using popsicle sticks. Right, Let's say you make a square 0:19:37.880 --> 0:19:41.159 out of popsicle sticks, and you joined the popsicle sticks 0:19:41.160 --> 0:19:43.560 together at the corners where the ends all meet. Ye, 0:19:43.680 --> 0:19:48.360 little Elmer's paste. Maybe makes sense. It seems pretty supportive, right, 0:19:48.440 --> 0:19:51.320 But when you pressed down on any one of those joints, 0:19:51.400 --> 0:19:54.840 which is where the load's going to be centered or 0:19:54.880 --> 0:20:00.920 distributed most remember the ends the square shift to the side, 0:20:00.920 --> 0:20:02.760 and all of a sudden you have a rhombus. Well, 0:20:02.840 --> 0:20:06.840 rambus is inherently less structurally sound than square, which is 0:20:06.840 --> 0:20:11.160 why you very rarely see rambus as in architecture. Right, 0:20:11.520 --> 0:20:13.920 with a triangle, when you press down at any one 0:20:13.920 --> 0:20:19.720 of the joints, it distributes that compression or tension directly 0:20:19.720 --> 0:20:24.080 through the center of the beam, so the triangle stays 0:20:24.160 --> 0:20:27.240 totally rigid. And when you add, the more triangles you add, 0:20:27.240 --> 0:20:30.320 the more support you have, So they're like basically like 0:20:31.080 --> 0:20:34.840 as far as the shape goes, the superconductor of transferring 0:20:34.960 --> 0:20:39.560 or distributing compression or tension. Yeah, that's a good way 0:20:39.560 --> 0:20:41.080 to put it. And that's why when you see that 0:20:41.080 --> 0:20:44.200 that train tress alone that has that trust on topics, 0:20:44.680 --> 0:20:49.639 got all those beautiful diagonal uh pieces of metal. And 0:20:49.680 --> 0:20:51.520 it's not just for for looks, even though it is 0:20:51.520 --> 0:20:54.159 cool looking. No. One of the other great things about 0:20:54.200 --> 0:20:57.000 a trust is that there you know, it's like just 0:20:57.119 --> 0:21:01.200 a three steel beams or three whatever aluminium beams. They're 0:21:01.240 --> 0:21:05.840 just three pieces of metal usually fixed together. And that's 0:21:05.920 --> 0:21:08.639 that's the other key that I left out. They have 0:21:08.760 --> 0:21:14.280 to be connected at the ends equally distributed from each end. Right, So, 0:21:14.359 --> 0:21:16.879 let's say you you drill a hole to to rivet 0:21:16.960 --> 0:21:19.720 one side of the trust to another, or one end 0:21:19.760 --> 0:21:23.080 of the trust to another end, the the other end 0:21:23.119 --> 0:21:26.480 has to be equally far away. Do you see what 0:21:26.560 --> 0:21:28.600 I'm saying. Yeah, yeah, okay, they wouldn't just be like 0:21:28.880 --> 0:21:31.280 just drill that other one wherever. So anyway you have 0:21:31.359 --> 0:21:35.720 to the place where the trust sides join together has 0:21:35.720 --> 0:21:38.080 to be on the ends. And then but one of 0:21:38.080 --> 0:21:40.919 the things that it allows for is for wind to 0:21:40.960 --> 0:21:44.520 blow through it easily. That's a huge point about trusses. 0:21:45.080 --> 0:21:50.080 They're not solid in that they don't they don't put 0:21:50.160 --> 0:21:52.240 up a lot of resistance to when they allow it 0:21:52.280 --> 0:21:54.320 to flow through, which is really kind of what you want. 0:21:54.440 --> 0:21:57.760 We'll see when you're building bridges. Yeah, I think even 0:21:57.800 --> 0:22:00.480 the covered bridges have is more of a that's type 0:22:00.520 --> 0:22:04.560 thing on the sides. Right. Yes, it's not solid, is it. 0:22:04.600 --> 0:22:08.080 That'd be dumb a covered bridge. Yeah. I thought the 0:22:08.080 --> 0:22:10.560 walls were usually like a lattice so wind could pass through. 0:22:10.680 --> 0:22:13.480 Now and they had a than a roof and like 0:22:14.040 --> 0:22:17.760 a lattice e side is there, right, Yeah, maybe there's 0:22:17.760 --> 0:22:21.320 all kinds. I think those are just to keep the 0:22:21.440 --> 0:22:25.200 rain off. Oh yeah, that's what you said earlier and 0:22:25.320 --> 0:22:31.080 keep shooting down there. Yeah. But anyway, trust is rock, 0:22:31.200 --> 0:22:33.680 I guess, is what I'm trying to say. Yes, there's 0:22:33.680 --> 0:22:37.720 your T shirt. Trusses rock. So are we at arches? 0:22:39.440 --> 0:22:42.520 Do we say that they frequently used trusses to support 0:22:42.880 --> 0:22:48.280 beam bridges? Yeah? Arches. Now, when we say a bridge 0:22:48.359 --> 0:22:52.520 is an arch bridge, the deck is not some big 0:22:52.600 --> 0:22:55.560 hill that you drive over. The deck is flat the 0:22:55.640 --> 0:23:01.240 arches underneath, uh right yeah. And you can have a 0:23:01.280 --> 0:23:04.080 single arch if your span isn't along, or you can 0:23:04.119 --> 0:23:06.760 have a big one with like six or eight arches. 0:23:07.480 --> 0:23:10.360 Although I've seen I think there are like short arch 0:23:10.440 --> 0:23:13.760 bridges that actually do go up and down, you know, 0:23:13.760 --> 0:23:17.480 like if there's natural arch bridges, like rock formations are 0:23:17.560 --> 0:23:19.960 like that and that's why they're still standing. There's um 0:23:20.000 --> 0:23:25.200 there's there's a bridge that forms like a perfect circle. 0:23:26.160 --> 0:23:28.760 So like when when you see it reflected in the water, 0:23:28.840 --> 0:23:33.480 it just looks like a circle. Arch bridges are pretty 0:23:33.480 --> 0:23:36.600 cool too. There are no trusses, but they're beautiful in 0:23:36.600 --> 0:23:39.919 their own way. That's true. Uh So the arches obviously 0:23:40.080 --> 0:23:43.040 semi circular. Um. And like you said, if it meets 0:23:43.040 --> 0:23:47.439 the water and reflects nicely, fully circular, fully circular. Uh 0:23:47.480 --> 0:23:51.119 And the entire form is gonna divert weight onto what 0:23:51.160 --> 0:23:54.960 are called abutments. And this is what takes on the pressure. 0:23:55.000 --> 0:23:57.840 It's like, I mean, if it's just a single arch, 0:23:57.920 --> 0:23:59.720 those abutments are probably going to be part of the 0:23:59.720 --> 0:24:04.119 earth on one side or the other. Yeah. Um. And 0:24:04.200 --> 0:24:07.119 the whole point of an abutment is when you press 0:24:07.160 --> 0:24:10.159