0 00:00:08,611 --> 00:00:10,791 - Now that we looked at the history of Roebling, 1 00:00:10,791 --> 00:00:14,891 and the education and his life experience, 2 00:00:14,891 --> 00:00:17,792 let's move on to his three major works 3 00:00:17,792 --> 00:00:20,392 beginning with the Niagara River Bridge, 4 00:00:20,392 --> 00:00:22,752 821 foot span, 5 00:00:22,752 --> 00:00:25,732 completed in 1855. 6 00:00:25,734 --> 00:00:28,370 In 1850, we talked about the Britannia Bridge 7 00:00:28,370 --> 00:00:30,650 in the UK by Stephenson. 8 00:00:30,650 --> 00:00:32,350 This was a railway bridge 9 00:00:32,350 --> 00:00:34,990 and it was intended to have suspenders, 10 00:00:34,990 --> 00:00:37,590 hence, the awkward, tall towers. 11 00:00:37,590 --> 00:00:42,310 The Niagara River Bridge at 821 feet needed those suspenders 12 00:00:42,310 --> 00:00:47,230 and it also needed a deep deck just like Britannia had. 13 00:00:47,230 --> 00:00:49,009 Here the span is much larger, 14 00:00:49,009 --> 00:00:52,449 therefore, the truss and the cables both are needed 15 00:00:52,449 --> 00:00:54,230 whereas, again, in the Britannia, 16 00:00:54,230 --> 00:00:56,730 only the deep deck was needed. 17 00:00:56,730 --> 00:00:59,289 The Niagara River Bridge essentially established 18 00:00:59,289 --> 00:01:01,930 Roebling's reputation as a master builder 19 00:01:01,930 --> 00:01:03,970 of suspension bridges. 20 00:01:03,970 --> 00:01:05,149 Roebling had a rival, 21 00:01:05,149 --> 00:01:07,310 just like Stephenson and Brunel were rivals, 22 00:01:07,310 --> 00:01:09,609 but they were rivals, but friends, 23 00:01:09,609 --> 00:01:11,610 Roebling was not friends with his rival 24 00:01:11,610 --> 00:01:13,910 and that rival was Charles Ellet. 25 00:01:13,910 --> 00:01:16,150 Charles Ellet actually was awarded this project 26 00:01:16,150 --> 00:01:18,730 for the Niagara River Bridge but 27 00:01:18,730 --> 00:01:20,230 before the project starts, 28 00:01:20,230 --> 00:01:23,851 Ellet gets fired for reasons unrelated to the project. 29 00:01:23,851 --> 00:01:26,490 While Roebling was building his Niagara River Bridge, 30 00:01:26,490 --> 00:01:29,011 the Wheeling Bridge over the Ohio River, 31 00:01:29,011 --> 00:01:31,430 another suspension bridge that was built by 32 00:01:31,430 --> 00:01:35,090 Charles Ellet, collapses in a wind storm. 33 00:01:35,090 --> 00:01:38,270 This gets Roebling nervous and he asks Trenton 34 00:01:38,270 --> 00:01:40,731 to send over more wire rope. 35 00:01:40,731 --> 00:01:44,131 So if you look at images of the Niagara River Bridge 36 00:01:44,131 --> 00:01:46,691 we see that he's attached the cables 37 00:01:46,691 --> 00:01:49,491 to the bottom of the deck down to the ground. 38 00:01:49,491 --> 00:01:52,971 So not a very elegant solution, but a safe one. 39 00:01:52,971 --> 00:01:56,892 And the Niagara River Bridge was safe against wind. 40 00:01:56,892 --> 00:01:59,252 During the Civil War, there was a concern that this bridge 41 00:01:59,252 --> 00:02:00,652 would be destroyed, therefore, 42 00:02:00,652 --> 00:02:02,975 Union soldiers guarded this bridge. 43 00:02:02,975 --> 00:02:05,855 It was considered an important bridge. 44 00:02:05,855 --> 00:02:08,615 Now let's move onto the Cincinnati Bridge. 45 00:02:08,615 --> 00:02:10,895 This was completed between the time period 46 00:02:10,895 --> 00:02:13,535 of 1856 and 1866. 47 00:02:13,535 --> 00:02:16,175 It was interrupted by the Civil War. 48 00:02:16,175 --> 00:02:18,055 This spans over the Ohio River 49 00:02:18,055 --> 00:02:20,880 and slightly over 1,000 feet in span. 50 00:02:20,880 --> 00:02:24,066 So we went from about 500 feet order of magnitude 51 00:02:24,066 --> 00:02:26,526 in the last lecture over in the UK 52 00:02:26,526 --> 00:02:28,626 with Telford, Stephenson, and Brunel 53 00:02:28,626 --> 00:02:31,986 and now we're up to in the order of magnitude of 1000 feet. 54 00:02:31,986 --> 00:02:33,926 And at the time that it was completed, 55 00:02:33,926 --> 00:02:37,266 it was the longest spanning bridge in the world. 56 00:02:37,266 --> 00:02:39,007 We can see with the Cincinnati Bridge 57 00:02:39,007 --> 00:02:41,127 the style that Roebling is developing. 58 00:02:41,127 --> 00:02:43,717 It's really the precursor, it's the prototype 59 00:02:43,717 --> 00:02:45,408 to the Brooklyn Bridge. 60 00:02:45,408 --> 00:02:49,868 Initially in 1846, Roebling had proposed two spans 61 00:02:49,868 --> 00:02:54,338 on the order of about 788 feet each. 62 00:02:54,338 --> 00:02:56,770 He revised that span to be one span 63 00:02:56,770 --> 00:03:00,470 after the successful completion of the Niagara River Bridge. 64 00:03:00,470 --> 00:03:01,870 So again, when completed, 65 00:03:01,870 --> 00:03:04,590 it was the longest spanning bridge in the world. 66 00:03:04,590 --> 00:03:07,070 Since it's completion, the Cincinnati Bridge 67 00:03:07,070 --> 00:03:09,450 has been renamed after the engineer. 68 00:03:09,450 --> 00:03:14,040 It is now called the John A. Roebling Bridge. 69 00:03:14,040 --> 00:03:15,651 So with this background of Roebling, 70 00:03:15,651 --> 00:03:17,851 his life, his experiences, 71 00:03:17,851 --> 00:03:20,911 we can examine now his greatest masterpiece, 72 00:03:20,911 --> 00:03:21,693 the Brooklyn Bridge. 73 00:03:21,693 --> 00:03:24,133 So the rest of the lecture will be dedicated 74 00:03:24,133 --> 00:03:27,513 to this masterpiece, the Brooklyn Bridge. 75 00:03:27,513 --> 00:03:29,493 So how did John Roebling's vision 76 00:03:29,493 --> 00:03:31,033 of the Brooklyn Bridge come about? 77 00:03:31,033 --> 00:03:33,273 It actually happened in 1852, 78 00:03:33,273 --> 00:03:35,873 that's when he got the idea for the Brooklyn Bridge. 79 00:03:35,873 --> 00:03:39,213 He was on a ferry boat, stranded on the East River, 80 00:03:39,213 --> 00:03:40,593 which is right behind me 81 00:03:40,593 --> 00:03:44,433 because chunks of clogged ice blocked the channel. 82 00:03:44,433 --> 00:03:46,533 He began dreaming and thinking about 83 00:03:46,533 --> 00:03:48,394 a bridge crossing this East River 84 00:03:48,394 --> 00:03:50,695 but it was a very large span and it would of 85 00:03:50,695 --> 00:03:54,597 had to be much longer than the Cincinnati Bridge. 86 00:03:54,597 --> 00:03:57,878 He wrote letters to the New York Press and eventually, 87 00:03:57,878 --> 00:04:02,119 in 1865, a bridge company was born. 88 00:04:02,119 --> 00:04:03,699 Now we're gonna examine the Brooklyn Bridge 89 00:04:03,699 --> 00:04:07,019 from the scientific, social, and symbolic aspects. 90 00:04:07,019 --> 00:04:09,019 So from the scientific aspect, 91 00:04:09,019 --> 00:04:10,579 we're gonna look at some terminology 92 00:04:10,579 --> 00:04:13,623 related to loads and the parts of a suspension bridge 93 00:04:13,623 --> 00:04:17,123 and look at the form that it has for gravity and wind. 94 00:04:17,123 --> 00:04:18,923 From the social point of view, 95 00:04:18,923 --> 00:04:21,263 there's a lot of politics to talk about 96 00:04:21,263 --> 00:04:23,703 and economy, of course, is closely related to 97 00:04:23,703 --> 00:04:26,063 both politics and the social context. 98 00:04:26,063 --> 00:04:28,183 And finally from the symbolic point of view, 99 00:04:28,183 --> 00:04:31,383 we know it to be on of the greatest icons in the world. 100 00:04:31,383 --> 00:04:34,903 We're gonna look at its opening and how the artist's 101 00:04:34,903 --> 00:04:37,045 respond to this bridge. 102 00:04:37,045 --> 00:04:39,705 A rendering drawn by one of John Roebling's assistants, 103 00:04:39,705 --> 00:04:42,925 Wilhelm Hildenbrand, shows what the vision 104 00:04:42,925 --> 00:04:45,305 of John Roebling was for the Brooklyn Bridge. 105 00:04:45,305 --> 00:04:47,525 So with this rendering, we can see that indeed, 106 00:04:47,525 --> 00:04:50,965 his vision, his original idea is what was constructed, 107 00:04:50,965 --> 00:04:53,265 or very similar to it. 108 00:04:53,265 --> 00:04:55,285 In the preface to report by John Roebling 109 00:04:55,285 --> 00:05:00,075 to the New York Bridge Company in 1867, he wrote, 110 00:05:00,075 --> 00:05:02,187 "The contemplated work when constructed 111 00:05:02,187 --> 00:05:03,987 "in accordance with my designs, 112 00:05:03,987 --> 00:05:06,387 "will not only be the greatest bridge in existence, 113 00:05:06,387 --> 00:05:08,148 "but it will be the great engineering work 114 00:05:08,148 --> 00:05:10,748 "of this continent and of the age. 115 00:05:10,748 --> 00:05:13,548 "It's most conspicuous features, the great towers, 116 00:05:13,548 --> 00:05:16,188 "will serve as landmarks to the adjoining cities, 117 00:05:16,188 --> 00:05:18,008 "and they will be entitled to be ranked 118 00:05:18,008 --> 00:05:20,128 "as national monuments." 119 00:05:20,128 --> 00:05:21,488 This isn't exactly modest, 120 00:05:21,488 --> 00:05:24,208 but actually history has shown it to be true. 121 00:05:24,208 --> 00:05:25,887 The towers of the Brooklyn Bridge actually, 122 00:05:25,887 --> 00:05:28,227 when completed, look like skyscrapers 123 00:05:28,227 --> 00:05:31,348 in the context of the Brooklyn and Manhattan skyline. 124 00:05:31,348 --> 00:05:34,447 Now I'll come back and show you that later. 125 00:05:34,447 --> 00:05:36,408 From the scientific aspect of the study, 126 00:05:36,408 --> 00:05:39,028 today I'm going to focus on some terminology, 127 00:05:39,028 --> 00:05:40,868 for example the loads. 128 00:05:40,868 --> 00:05:43,128 In engineering, we call dead load 129 00:05:43,128 --> 00:05:45,751 something that's a permanent load in the structure. 130 00:05:45,751 --> 00:05:48,491 It's essentially the self weight of the structure. 131 00:05:48,491 --> 00:05:51,471 So in the case of the Bridge, it's the load of the deck 132 00:05:51,471 --> 00:05:54,471 for example, would be something to be considered 133 00:05:54,471 --> 00:05:56,931 the dead load of that bridge. 134 00:05:56,931 --> 00:05:58,551 Then we have live load. 135 00:05:58,551 --> 00:06:00,191 Live load, in the case of a bridge, 136 00:06:00,191 --> 00:06:02,371 is the traffic load, the weight of the vehicles, 137 00:06:02,371 --> 00:06:03,771 the weight of the pedestrians. 138 00:06:03,771 --> 00:06:07,011 It's a transient load, something that's moveable. 139 00:06:07,011 --> 00:06:09,591 That's what we refer to as live load. 140 00:06:09,591 --> 00:06:12,731 We also have wind forces on any structure 141 00:06:12,731 --> 00:06:14,571 buildings as well as bridges. 142 00:06:14,571 --> 00:06:17,292 So we'll talk about a little bit about those wind forces 143 00:06:17,292 --> 00:06:19,852 and what part of the suspension bridge, 144 00:06:19,852 --> 00:06:21,752 the Brooklyn Bridge in particular, 145 00:06:21,752 --> 00:06:24,292 is dealing with those wind forces. 146 00:06:24,292 --> 00:06:26,032 Let me explain to you a little bit about 147 00:06:26,032 --> 00:06:27,612 the different parts of the bridge 148 00:06:27,612 --> 00:06:30,535 and the terminology used to describe the different parts. 149 00:06:30,535 --> 00:06:34,475 We have the deck, and the deck of the bridge 150 00:06:34,475 --> 00:06:36,415 is supported by the suspenders. 151 00:06:36,415 --> 00:06:38,974 The suspenders are the vertical elements 152 00:06:38,974 --> 00:06:41,935 of a suspension bridge and these elements 153 00:06:41,935 --> 00:06:44,635 essentially pick up the load of the deck truss 154 00:06:44,635 --> 00:06:48,415 which carries the dead load and the live load. 155 00:06:48,415 --> 00:06:50,475 And the suspenders, then in turn 156 00:06:50,475 --> 00:06:53,275 transfer their loads to the cables. 157 00:06:53,275 --> 00:06:58,115 The cables are the draped cable that goes from 158 00:06:58,115 --> 00:07:00,476 the top of one tower to the top of the other 159 00:07:00,476 --> 00:07:03,657 and then back anchored against the anchorages 160 00:07:03,657 --> 00:07:05,917 of these suspension bridges. 161 00:07:05,917 --> 00:07:07,997 The cables transfer the load to the anchors 162 00:07:07,997 --> 00:07:09,777 but also to the towers. 163 00:07:09,777 --> 00:07:13,877 And the towers bring the load down to the foundation. 164 00:07:13,877 --> 00:07:15,637 In the case of the Brooklyn Bridge, 165 00:07:15,637 --> 00:07:17,257 we have stays. 166 00:07:17,257 --> 00:07:19,697 Stays are the diagonal elements. 167 00:07:19,697 --> 00:07:20,977 They're like the suspenders. 168 00:07:20,977 --> 00:07:22,636 The suspenders are vertical, 169 00:07:22,636 --> 00:07:24,257 the stays are diagonal. 170 00:07:24,257 --> 00:07:26,978 And they essentially control the deformations 171 00:07:26,978 --> 00:07:30,557 that could be induced by the dynamic effects of wind. 172 00:07:30,557 --> 00:07:32,437 So Roebling learned this lesson 173 00:07:32,437 --> 00:07:34,337 through the Wheeling Bridge collapse 174 00:07:34,337 --> 00:07:37,197 and he applied those cables tying down the 175 00:07:37,197 --> 00:07:39,697 Niagara River Bridge from the bottom of the deck 176 00:07:39,697 --> 00:07:41,687 down to the ground, 177 00:07:41,687 --> 00:07:44,120 a solution that wasn't very elegant. 178 00:07:44,120 --> 00:07:46,300 In the case of the Cincinnati Bridge 179 00:07:46,300 --> 00:07:48,140 and also the Brooklyn Bridge, 180 00:07:48,140 --> 00:07:51,020 he includes these stays, these diagonal elements, again, 181 00:07:51,020 --> 00:07:54,160 to control the possible deformations due to wind 182 00:07:54,160 --> 00:07:56,480 through the lessons that he was learning 183 00:07:56,480 --> 00:07:58,300 of the bridges that were having trouble 184 00:07:58,300 --> 00:08:01,420 due to wind induced vibrations. 185 00:08:01,420 --> 00:08:03,820 Some other terminology that you've heard of before 186 00:08:03,820 --> 00:08:06,860 but I'm going to apply it in the context 187 00:08:06,860 --> 00:08:10,740 of structural engineering is compression and tension. 188 00:08:10,740 --> 00:08:14,680 So compression is when an element is being squeezed together 189 00:08:14,680 --> 00:08:17,980 and tension is when the element is being pulled apart. 190 00:08:17,980 --> 00:08:19,460 So when we look at a structure, 191 00:08:19,460 --> 00:08:22,220 we have to be able to identify which parts 192 00:08:22,220 --> 00:08:25,660 are in tension and which parts are in compression. 193 00:08:25,660 --> 00:08:28,340 Because that is the foundation of how one goes about 194 00:08:28,340 --> 00:08:30,900 designing those elements. 195 00:08:30,900 --> 00:08:32,960 So I have a question for you, 196 00:08:32,960 --> 00:08:36,300 if you look at this Brooklyn Bridge, look at the tower, 197 00:08:36,300 --> 00:08:39,920 the cables, the cables again, are the elements that go from 198 00:08:39,920 --> 00:08:42,980 tower to tower, they drape from tower to tower, 199 00:08:42,980 --> 00:08:45,420 and look at the suspenders, those vertical elements 200 00:08:45,420 --> 00:08:48,820 carrying the load from the deck to the cable. 201 00:08:48,820 --> 00:08:51,040 Which of those elements are in tension, 202 00:08:51,040 --> 00:08:54,789 and which of those elements are in compression? 203 00:08:59,630 --> 00:09:02,740 The answer to the question of which elements are in tension 204 00:09:02,740 --> 00:09:05,720 and which elements are in compression is Option A. 205 00:09:05,720 --> 00:09:08,660 It shows that the tower is in compression, 206 00:09:08,660 --> 00:09:13,340 the cable is in tension and the suspenders are in tension. 207 00:09:13,340 --> 00:09:16,562 So through your homework assignments that you will be doing, 208 00:09:16,562 --> 00:09:18,781 you will be able to understand this more fully 209 00:09:18,781 --> 00:09:23,002 and also be able to calculate the actual forces and stresses 210 00:09:23,002 --> 00:09:25,522 that these elements are carrying. 211 00:09:25,522 --> 00:09:27,521 To continue the story of the Brooklyn Bridge, 212 00:09:27,521 --> 00:09:30,142 I need to introduce to you Washington Roebling. 213 00:09:30,142 --> 00:09:33,061 Washington Roebling is one of John Roebling's sons 214 00:09:33,061 --> 00:09:35,562 and he received his degree in civil engineering 215 00:09:35,562 --> 00:09:39,701 from the Rensselaer Polytechnic Institute, known as RPI. 216 00:09:39,701 --> 00:09:41,462 It's a great school for engineering 217 00:09:41,462 --> 00:09:43,063 and one of the first engineering schools 218 00:09:43,063 --> 00:09:44,963 in the United States. 219 00:09:44,963 --> 00:09:47,003 He was a colonel in the Civil War 220 00:09:47,003 --> 00:09:50,123 and he worked with his father on the Cincinnati Bridge. 221 00:09:50,123 --> 00:09:52,543 Towards the end of that Cincinnati Bridge project, 222 00:09:52,543 --> 00:09:54,963 Roebling, actually Washington Roebling I should say, 223 00:09:54,963 --> 00:09:56,883 actually took over most of that project 224 00:09:56,883 --> 00:09:59,603 because John Roebling was busy preparing 225 00:09:59,603 --> 00:10:01,483 for the Brooklyn Bridge. 226 00:10:01,483 --> 00:10:04,683 Eventually, Washington Roebling took over the construction 227 00:10:04,683 --> 00:10:07,124 of the Brooklyn Bridge as well. 228 00:10:07,124 --> 00:10:10,185 In 1869, while surveying the East River determining 229 00:10:10,185 --> 00:10:13,388 where exactly to place this Brooklyn Bridge, 230 00:10:13,388 --> 00:10:16,248 John Roebling was standing on the piles of a dock. 231 00:10:16,248 --> 00:10:19,687 As the ferry docked and pushed back those piles, 232 00:10:19,687 --> 00:10:22,228 his toes got crushed. 233 00:10:22,228 --> 00:10:23,909 He refused medical attention, 234 00:10:23,909 --> 00:10:26,589 he believed in the healing power of water 235 00:10:26,589 --> 00:10:27,829 and tried his own methods, 236 00:10:27,829 --> 00:10:29,609 but unfortunately they didn't work 237 00:10:29,609 --> 00:10:33,509 and two weeks later, John Roebling died of lockjaw. 238 00:10:33,509 --> 00:10:36,329 Fortunately his son, Washington Roebling, 239 00:10:36,329 --> 00:10:38,149 was educated in civil engineering 240 00:10:38,149 --> 00:10:40,329 and he takes over the project. 241 00:10:40,329 --> 00:10:42,369 Washington Roebling was a great builder 242 00:10:42,369 --> 00:10:45,669 and a great engineer and well prepared to handle 243 00:10:45,669 --> 00:10:48,389 what we would call, say, the technical aspects 244 00:10:48,389 --> 00:10:50,169 of bridge construction. 245 00:10:50,169 --> 00:10:53,389 But he was not prepared for the social part, 246 00:10:53,389 --> 00:10:57,542 meaning the politics and corruption that would follow.