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‐The 3 bridges we will deal with were built in mid 19th c. They were very controversial. A lot of politics were involved because of the size of the structures and the funds invested in them
‐Treat as works of art and as results of competition‐Shouldn’t get the idea that Structural Art is confined to huge works. It also applies to relatively small bridges and buildings‐In each case the bridge was designed by one person –structural artist. Best engineers of their era.
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Before the ET, Eiffel was Europe’s greatest bridge builder in mid 19th century
Raised in a middle class family, born in Dijon
Failed the entrance exam for the prestigious Ecole Polytechnique so he enrolled in the private Ecole Central des Arts et Manufactures
Graduated in 1855 with a degree in Chemical engineering.
Was supposed to enter the family vinegar business, but family feud, and therefore he took a job with a firm that designed and built railway equipment.
By 1867 he left this firm and established his own firm as a designer and builder of metal construction.
By 1885 he had built hundreds of major iron structures
Image of ET from http://en.wikipedia.org/wiki/File:Tour_Eiffel_Wikimedia_Commons.jpg
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Symbolic: we have examined the Eiffel Tower as a work of art, now we examine Eiffel as the artist.
Eiffel has said “the more a system is simple, the more one can be sure of how the loads will be carried”
His aesthetic, I would suggest, was rooted in simplicity and expression of the relationship between form and forces.
Le Corbusier (famous architect) has said that Eiffel “was pained by not being seen as a creator of beauty… His calculations were always inspired by an admirable instinct for proportion, his goal was elegance.”
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•Railroad bridge – need to have it fairly straight (not much slope)
•Towers – exceptionally high because the valleys are deep and wide, so spans are reasonable for a railroad bridge
•Idea is to connect all county seats with straight lines
•http://transpressnz.blogspot.com/2011/12/rouzat‐viaduct.html
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•Eiffel flares out columns at base, not satisfied with before
•Doesn’t like straight towers
•Flare = aesthetic choice
•but at same time, he’s the builder so he’s concerned with economics
•Spread at base to spread forces out on foundation
•Trying to not waste materials, not waste money, but still be elegant
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•Tries to express the structure
•Not only splays but gets closer together due to the nature of the water, is more streamlined for when it floods
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‐Competition shows us the state of the art at the time‐All entries were from designer‐builders (designers who were also the builders) so they gave costs for building their designs‐Describe first entry
‐Like Eads showed: connecting deck to arch with maze of truss‐An ambiguous form like the Saltash and Britannia ‐Spreads at supports due to lateral affect of the winds
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‐2nd entry – shape of the moment diagram for a beam = rational‐Rational does not guarantee elegance‐One still needs to make aesthetic choices
‐The structure can be hidden, exposed, or exposed and expressed(as this one)
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‐3rd entry‐Shorter span but needs more pillars expensive, so try to avoid‐Pier in main channel more difficulty in construction
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‐4th entry‐Almost equal spans and relatively heavy deck‐Pier in middle, plain truss
‐Each is a reasonable solution
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‐5th entry‐Cantilever joined in middle‐Very heavy supporting towers
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‐6th entry ‐Ambiguous form
‐See all these different forms that people were exploring‐Biggest design competition in Europe at the time, possibly the world
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‐7th entry = 2nd lowest cost design‐Broken arch; slightly gothic looking ‐Leaning supports for center of span
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‐8th entry Eiffel’s design ‐Winner‐31% lower in cost than 2nd cheapest design ‐Truss is much lighter because it uses the arch to support more
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‐Eiffel’s design ‐New aesthetic‐Background for Garabit
‐http://portoloungehostel.com/wp‐content/uploads/2012/03/DMaria1.jpg
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‐For Garabit, Eiffel has shown that he was the best no competition, but a commission‐Not that one is superior to the other – they are very close‐In the top, the deck merges into the top of the arch, but in the Garabit Eiffel is careful to express the arch and deck separately‐Presumption: he preferred the Garabit solution
‐Also rational because the height is greater in the Garabit than the Pia Maria‐For Garabit, Eiffel has shown that he was the best no competition, but a commission
‐https://www.flickr.com/search/?text=garabit&sort=date‐posted‐desc&license=1%2C2%2C3%2C4%2C5%2C6 (photo Tim Kelly)
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‐Comparison ‐ Almost the same in span‐Not that one is superior to the other – they are very close‐In the top, the deck merges into the top of the arch, but in the Garabit Eiffel is careful to express the arch and deck separately‐Presumption: he preferred the Garabit solution
‐Also rational because the height is greater in the Garabit than the Pia Maria
‐http://www.skyscrapercity.com/showthread.php?t=200745‐https://www.flickr.com/search/?text=garabit&sort=date‐posted‐desc&license=1%2C2%2C3%2C4%2C5%2C6 (photo by Olibac)
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‐Built the same as the Eads Bridge‐Eiffel was a builder, so needed to be able to build it economically‐Not temporary supports for cable, but real supports
‐https://www.flickr.com/search/?text=garabit&sort=date‐posted‐desc&license=1%2C2%2C3%2C4%2C5%2C6 (photo Tim Kelly)
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‐Construction‐Hinged at base (defines hinge)
‐Hinges can adjust arch so that it meets at the center‐Improvement over Eads which was fixed at the base (why he had to use ice to adjust)‐Allows for expansion and contraction due to temperature change‐Construction and aesthetic decision
‐Cables holding arch in place
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https://www.flickr.com/search/?text=garabit&sort=date‐posted‐desc&license=1%2C2%2C3%2C4%2C5%2C6 (by Frederic Bruschet)
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‐Comparison by a professor in Vienna with a German bridge, the Mungstener Viaduct, in his book Aesthetics of Bridges produced in the early 20th c. ‐Where Garabit comes to a point at the base of the arch, Mungstener is actually wider at the base‐Eiffel separates the pier from the arch while in the Mungstener the pier clunks into the arch‐Eiffel’s piers in the middle are the same as the ones on the side, but they are completely different in Mungstener‐Same kind of design but visually very different
‐https://www.flickr.com/search/?text=garabit&sort=date‐posted‐desc&license=1%2C2%2C3%2C4%2C5%2C6 (photo Tim Kelly)
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Mungstener is technically correct and quite inexpensive but quite different due to different aesthetic vision
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‐Closer look at Garabit‐See the separation between tower and hinge
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‐ Side with scale factor
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‐Exhibited in an important place – 200 Franc note‐Now switched to Euro and depersonalized all currency
‐Same view in note
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‐One design that was not so clever…‐Firth of Tay – structure was unstable collapse 75 people die‐Compare towers Firth of Tay’s are too slender and ugly
‐http://commons.wikimedia.org/wiki/File:Catastrophe_du_pont_sur_le_Tay_‐_1879_‐_Illustration.jpg
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‐2 great barriers to Scotland’s east coast travel were the Firth of Forth and the Firth of Tay‐When the Firth of Tay collapsed, the same engineer was in the process of building a bridge over the Firth of Forth (foundations were built). Had planned a 2‐span suspension bridge of 1600 ft each. But when the F of Tay collapsed the public lost confidence in him and his design and a new design was requested of Benjamin Baker.‐Next time Scots had to build a bridge over a stormy estuary they wanted to make sure it would not fail
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‐Thought to be monstrous by some‐Clearly designed to resist the heavy wind‐Benjamin Baker designed on the basis of this failure
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‐Looks better from profile view‐Longest spanning bridge in the world and also a RR bridge great achievement
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‐Reminds us of the Eiffel Tower turned on its side‐Double cantilever‐Relatively light but very very stiff‐Overdesigned, but Baker was concerned with aesthetics
‐Not all agree, but intention was there
‐Photo by Maria Garlock
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Photo by Maria Garlock
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Once the cantilever arm was constructed, the center span was prefabricated on the ground and then lifted into place using a large crane.
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Poll Title: What is the magnitude of the reaction at the anchor Ra (in terms of W)?
http://www.polleverywhere.com/multiple_choice_polls/92KDwgHD0T5zuDt
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‐ Benjamin Baker demonstrating to the government how this new form would work. Used this in his presentation.
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Poll Title: Which image properly represents the tension and compression in the structural elements?
http://www.polleverywhere.com/multiple_choice_polls/aJQHgDtpN0BxUKt
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‐Eads Bridge, Across the Mississippi River in St. Louis– requires a stiff span because of railroad crossing. First bridge to be built entirely out of steel‐Garabit ‐ deep valleys. High viaducts are subject to heavy winds; Garabit Viaduct: way up wind loads important‐F of F ‐ Estuaries (in every major port) – rough – stiff, long spans ‐ new forms
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‐Had no formal training ‐largely self‐educated; at the age of 13, he left school to take up work to help support the family‐Born and raised on the Ohio River‐made his initial fortune in salvage, by creating a diving bell for retrieving goods from the bottom of rivers that were sunk there by riverboat disasters, especially along the busy Mississippi River. He also devised special boats for raising the remains of sunken ships from the river bed. When steamboats sunk you could keep anything you salvage from the bottom‐Designed a diving bell (submarine) and walked on the bottom of the Mississippi River knew the river intimately‐Close friend of Ulysses S. Grant and during the Civil War designed and built a fleet of metal boats that controlled the Mississippi River for the North‐In 1870s and 80s designed a system of jetties for New Orleans to open up the port (which was closing due to silt) against the competition of the government Corps of Engineers‐Influenced by his walks along the Mississippi River
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‐Eads was not in great health due to salvaging (weak heart) ‐Went to Germany after the Civil War and rode up and down the Rhine‐See this bridge in Koblenz, Germany
‐Uses triple arch idea for his bridge‐Stimulated like many other engineers by seeing previous works
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But his proposal was different: steel, not iron; and 520 ft in span = 50% longer than Coblenz1st bridge he ever designed. Never designed one before or after. Hired 2 assistants/engineers who had the detailed structural experience that he lacked.Like Bakers F of F, it is the only MAJOR bridge design he had done.
http://www.cityprofile.com/missouri/photos/2454‐st.‐louis‐eadsbr1.html
Flikr has some CC images, but none have the arch in the background. For lecture, keep this one.https://www.flickr.com/search/?text=EADS%20BRIDGE&sort=date‐posted‐desc&license=1%2C2%2C3%2C4%2C5%2C6
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‐Symbolic: Probably the first bridge in the US to be designed explicitly as a symbol of civic art. St L. consciously set out to create a monument to symbolize its aspirations of reestablishing economic dominance in the Mid west.
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‐Social: Competition for dominance in the Midwest after Civil War; RR started to come from East to Chicago‐Traditional metropolis was St. Louis until the Civil War. The Civil War however cut off river transportation and St. Louis was in danger of losing dominance to Chicago‐St. Louis Bridge (now the Eads Bridge) was an effort to draw the RR through St. Louis (Chicago wanted it through Chicago) and connect St L to the prosperous NW and the expanding west.
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‐https://www.flickr.com/search/?text=EADS%20BRIDGE&sort=date‐posted‐desc&license=1%2C2%2C3%2C4%2C5%2C6 (by MoDOT)
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‐If take strings and place loads get funicular shape pure tension‐If freeze that form and turn it upside down all compression
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‐Eads needed to raise money for this bridge because the government would not sponsor it‐Convinced bankers in NYC that this is a profitable invention‐This image is part of the report to bankers (Fig. 7)‐ Arch: this is the perfect form for a bridge for uniform loads
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‐But if train is on one side only instability‐Danger of the arch form – good only for one load type
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‐What you need is a deck with bracing, truss, to stiffen the arch enough to carry a side load‐Deep on the sides to combat motion downwards‐Eads said that this was not attractive
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‐Eads prefers this shape‐Takes arch material and splits it into two pieces (same amount of material) and laces it together
‐Exactly what Telford did (trussed arch)
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‐Weight of side load is transferred vertically to the truss arch‐Design of 1860s no automobiles
‐2 levels: trains and carriages‐Eads is trying to make it as light as he can, but still very stiff
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‐Completed in 1874‐First major structure made out of steel, not iron
‐Explain difference: carbon content and alloys‐Similar to Britannia, except Britannia is more closed‐in‐Trussed arch is similar to Eiffel’s but the first one made out of steel‐See it the way it looks today with trains going through it (taken about 30 years ago)‐Was taken out of service for trains 20 years ago (I think that today have metro??)
‐Problem of how to preserve it‐Still viable for automobiles
‐National landmark
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‐See similarity with Telford’s design‐Explain difference between the 2 designs of Telford (Craigellachie and Mythe)
‐Direction of the Xs ‐Eads has simpler, more modern approach‐Eads knew what Telford had done
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‐Construction of Eads Bridge‐Eads designed how this bridge would be built on the Mississippi River‐Don’t see much, but a major part of the bridge is already built. See Caissons in the Mississippi River‐Base of river is moving all the time, so if tried to found it on the sediment, the bridge would fail‐River is too wide for a single span at this timea
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‐Compressed air caissons driven down with sheets of wood‐Will see again next time with the Brooklyn bridge‐Big metal cylinder which cuts its way down to solid ground‐Then send people down there to clean muck out‐Stones piled on to make piers
‐Method developed in Europe that Eads and Roebling were both familiar with ‐Water would crush caissons in it if the air inside were not compressed
‐Pressure (hydrostatic) proportional to depth needed to pump air to resist pressure‐Need to bridge people up slowly to avoid getting bends (called then caisson disease)
‐Describe the medical condition‐Some died‐Eads and his doctor discovered this solution but did not communicate to Roebling (building the Brooklyn Bridge) since they were rivals
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‐Here’s the superstructure‐Built out as cantilevers to avoid interrupting river traffic‐Temporary cables and towers to avoid scaffold in the water‐Temperature meant that it moved a lot so he had to pack it with ice to shrink it so that he could make the connections at the middle secure
‐https://www.flickr.com/search/?text=EADS%20BRIDGE&sort=date‐posted‐desc&license=1%2C2%2C3%2C4%2C5%2C6 (by MoDOT)
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‐The Eads Bridge today = a great work of structural art‐National Historic Landmark‐Didn’t bring greatness in the way that they hoped (St. Louis is a great city, but not the gateway to the West)‐Bridge served purpose but was not able to pay back investors because there was less traffic than anticipated‐Steel needs to be painted‐Locomotives got heavier‐Traffic was reduced after WWII
‐https://www.flickr.com/search/?text=EADS%20BRIDGE&sort=date‐posted‐desc&license=1%2C2%2C3%2C4%2C5%2C6 (by Kent Landerholm)
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‐Deal with these 3 people‐Eads – his design; big competition for dominance in the Midwest between St. Louis and Chicago‐Eiffel‐Baker – new character; distinguished civil engineer; this is the only bridge he built
‐Treat each of these as designs by artists‐Although each of these people had a major career in engineering, Eads and Baker had only one major work associated with their names
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