Short Answer Bridges
What scientific phenomenon brought about the collapse of the Tacoma Narrows Bridge?
"Self-excitation" or "aeroelastic flutter"
Explain why Prof. Garlock argued that the Golden Gate Bridge is not a work of pure structural art.
Although the GG Bridge is considered an art deco cultural icon of San Francisco, the bridge is not pure structural art because we cannot entirely see the structure. Due to the facade concealment, it cannot be considered structural art because structure itself needs to form elegance.
Name 3 bridges that Ammann designed of record-breaking spans?
Bayonne Bridge, George Washington Bridge, Verrazano Narrows
"Out of Many - One" - the motto of the US. How does this apply to the "social" meaning of the Eiffel tower and Washington Monument?
Both are made of many pieces or stones but create a single structure. Also, they united the nation (and world) through their construction.
Describe the construction method used for both the Felsenau Bridge and the Ganter Bridge and why it is advantageous.
Both the Felsenau and the Ganter were constructed using the balanced cantilever method. This method is advantageous because it is specifically helpful for the building of cable-stayed bridges such as these. Once segments are placed, they will be supported by new cable stays in each construction stage. No auxiliary supports are required = economical and practical method for long cable-stayed bridges
Maillart's evolution of the 3-hinged hollow box arch went from smooth arches to "broken" arches. Name one bridge of the "broken arch" style and sketch the differences between the two forms.
Broken: Felsegg, Vessy, Lachen, Garstatt
Place these materials in chronological order: o reinforced concrete o structural steel o cast/wrought iron o prestressed concrete
Cast/wrought iron 2. Structural steel 3. Reinforced concrete 4. Prestressed concrete
For Menn's Felsenau Bridge, describe one characteristic illustrating "discipline" and one other illustrating "play".
Characteristics illustrating discipline (meaning they follow engineering guidelines/safety/rules: Double columns Pre-stressing in 2 directions Characteristics illustrating play aka creativity/aesthetic/artistic freedom: Single box girder with overhangs Haunched and integrated form Curved roadway
Who was the person who was erased from the history of the Golden Gate Bridge design until recently? What was his role and why did he get no credit?
Charles Ellis Ellis was considered only a secretary, however, after creating the bridge design and being known as the "brains" of the operation, Strauss fired Ellis due to jealousy
Name two bridges designed by Brunel?
Clifton Bridge (1864) and Maidenhead Bridge (1835)
Why is creep an important consideration in prestressed concrete?
Creep is an important consideration because it describes the physical quality of the concrete after it has been subjected to shrinkage and overall shortening of material, which causes the area to decrease and cause issues. Creep = length shortening under constant stress/load You have to take into account creep in order to build a safe bridge.
Name and describe three kinds of loads on a bridge.
Dead load: permanent vertical load, fixed position, static Traffic Load (live load): transient loads, movable positions Wind Force: transient, dynamic, horizontal load
Deflection theory led to thinner spans. What was the rationale behind deflection theory - in other words, what component of the bridge was relied upon for stiffness?
Deflection theory contained three parts: The heavier the span weight (qL), the greater the cable tension The greater the cable tension, the stiffer the span The stiffer the span, the less need for deck trusses
Who designed the Walnut Lane Bridge in Philadelphia and why is it significant?
Designer of Walnut Lane Bridge: George Webster and Henry Quimby At the time it was built, there was no direct connection It was more than a bridge: it was a way forward into a new century Connects two neighborhoods in Philly over a deep gorge Longest and highest concrete arch in the world when built
Describe with a sketch two types of cable-stayed arrangements.
Fan-shape cables: Fan out/radiate from a single point Harp-shape cables: The cables are all parallel
What construction method, extensively used today, did Finsterwalder invent?
Finsterwalder invented the "free-cantilever construction" method for prestressed concrete bridges, which allowed for long span bridges to be built without stabilized shoring.
Who was the one to pioneer prestressed concrete and what was the greatest scientific challenge to advancing it?
Freyssinet was the one to pioneer prestressed concrete Greatest scientific challenge to advancing it: CREEP
Other than not placing the stone façade on the towers, how did Othmar Ammann achieve economy in the design of the George Washington Bridge?
He was able to adjust the load calculations because he realized the low probability of full truck loading. This saved a lot of money during construction.
What are two ways that bridges were reinforced to counter the aerodynamic effects of wind after the collapse of Tacoma Narrows?
In order to counter the effects of the wind, retrofits were added which provided lower bracing
Menn described the hierarchy of his design goals as a dart board (see image). Label the numbers with one of these design goals: economics, safety, serviceability, aesthetics.
Inner circle = aesthetics Economy Serviceability Safety
Two short arch bridges of equal span are built: one in stone and another in iron. Which one will likely weigh less and why?
Iron will weigh less. It is lighter than stone and more permanent than wood.
What was the difference between Lindenthal's aesthetic and Ammann's aesthetic?
Lindenthal preferred massiveness while Amman preferred lightness
What is the visual difference between the Pia Maria Bridge and the Mungstener Bridge?
Pia Maria has a hinged support at the base of the arch, and the Mungstener has a fixed support. Again, the deck of the Pia Maria merges into the top of the arch.
Conceptually, how does prestressing work and why is it advantageous to concrete?
Prestressing is the introduction of compressive force to the concrete in order to counteract the stresses that will result from an applied load. This is done by embedding high tensile steel tendons within the concrete. In other words, the concrete is compressed (squeezed) before applying the load. Advantages for Concrete: Makes it more economical and durable Safer for long spanning bridges Allows for more exotic forms, new forms, innovation
What innovation allowed Menn to span a longer distance between the cross-walls in the Reichenau bridge compared to Klosters Bridge?
Prestressing of the deck allowed Menn to span a longer distance between the cross-walls in the Reichenau bridge.
Sketch two types of cross walls that Maillart used and name the bridge that he used them on.
Rectangular cross walls: Valtchielbach 1925 Trapezoidal cross walls: Schwandbach 1933
The Britannia and Menai Bridge both cross the Menai Straight. Name the designer of each bridge and what kind of traffic it was designed for (carriage or locomotive).
Robert Stephenson designed the Britannia Bridge and is meant for locomotives. William Telford designed the Menai Bridge and is meant for carriages.
The Wheeling Bridge collapse prompted Roebling to do what on the design of the Niagara Bridge?
Roebeling heard about Wheeling Bridge collapse and added more wire rope to tie to the bottom of his bridge for the construction of the Niagara Bridge
Name two ways that steel "completes" (i.e. complements) concrete in reinforced concrete structures.
Steel is ductile and excellent in tension therefore it reinforces the brittle and poor in tension concrete.
Where and with whom did the definition and ideals of structural art begin?
Structural art was started in Scotland by Thomas Telford in the 18th century.
The aesthetic goals of Menn were (1) transparency and slenderness, (2) simplicity and regularity, and (3) artistic shaping. Pick one of these and describe how the Sunniberg achieves this goal.
Sunniberg Bridge: I. Transparency and slenderness Open piers, thin deck Artistic shaping Harp cable form, similar piers, symmetric profile Expansion joints are used due to changes in temperate He uses a curve to account for this (less expensive approach) The bridge needs to withstand harsh temperatures Simplicity and regularity Folded pier section and outward splay of piers There is shaping to give it a more interesting appearance
Describe the load path on a suspension bridge considering the following components: towers, deck, cables, suspenders.
Suspenders: pick up load of deck truss Cables: pick up load of the suspenders Towers: pick up the load of the cables and takes load to the foundation
L/d defines the form of a suspension bridge. Will a smaller or larger L/d value produce a larger force in the cables? Why?
Taller towers mean smaller cable forces ... this would mean a larger d (so smaller L/d) means less cable force
The evolution of the structural artist has been described in three phases: imitation, innovation, and inspiration. Place these three bridges by Maillart into the proper phase: Tavanasa Bridge, Stauffacher Bridge, Salginatobel Bridge.
Tavanasa Bridge: Innovation in form: expressing 3 hinges of the structure (rational but to radical) Stauffacher Bridge: Imitation in form: designed like renaissance bridge, 3-hinged arch - but had to be a 'fake' design (cover structure) Salginatobel Bridge: Inspired in form: smooth hollow box arch
On a sketch of the Firth of Forth, mark the elements that are in compression and tension.
Tension: top of anchor arms and cantilever arms Compression: bottom of anchor arms and cantilever arms
Sketch the difference between the Craigellachie and Mythe bridge. Who designed them and which one is more efficient?
The Craigellachie and Mythe Bridges were designed by Thomas Telford. The Craigellachie has bisectors of the diagonal perpendicular to the arch whereas the Mythe has bisectors of the diagonal that are vertical (making it more efficient).
How is the shape of the Eiffel Tower related to the forces acting on it?
The Eiffel Tower's shape matches the moment diagram of the forces acting on it. This proper form of the structure leads to efficiency.
The Eiffel Tower and Rainier Tower are shown to the right. Which form is most efficient for carrying wind loads and why? (You may use a sketch to help with your response, but not necessary.)
The Eiffel tower is more efficient than the Rainier tower because it matches the shape of the moment diagram (aka built to withstand the force acting on it). On the other hand, the Rainier tower is not really utilizing the used material by having the bottom with a smaller area than the top.
What makes the Eiffel Tower so light? Is the form dominated by the forces of gravity or wind?
The Eiffel tower is very light due to the material (iron) and design (many whole, weighs less than the air that surrounds it).
What structural system is the Firth of Forth Bridge? Suspension, arch, etc.
The Firth of Forth Bridge is a Horizontal cantilever, with part of the structure working in tension and another working in compression.
What is the "scientific" explanation for why the area of the Washington Monument is larger at the base?
The Washington Monument has a greater cross-sectional area at the base because it has to withstand more force the further down the structure it is. This means less material is needed to support the force near the top versus the bottom.
Steel reinforcement is placed on the bottom of simply supported concrete beams and on the top of cantilever beams. Why is this?
The bottom steal is in tension and the concrete cannot resist tension
What is the visual difference between the Pia Maria Bridge and the Garabit Bridge?
The deck merges into the top of the arch in the Pia Maria but in the garabit, the deck sits on top of the arch
Which form is more efficient: the hollow box of the Zuoz Bridge or the solid arch of the Stauffacher Bridge? Why?
The hollow box of the Zuoz Bridge is more efficient because it uses 3x less material and is still stiffer/stronger
What were the two fundamental changes of the Industrial Revolution that served as a catalyst for Structural Art?
The industrial revolution saw both a change in material (wood and stone to iron) and power source (animal and human to steam).
If the legs of the Eiffel Tower were further apart, would the forces increase or decrease? Why?
The legs being spread further apart would decrease the force on them because it would spread it over a greater area.
What was "dishonest" about the form of the Hellgate Bridge?
The top chord is not doing anything at the supports and the bottom chord transfers all of the load to the foundation
What do the Eads bridge and Craigellachie Bridge have in common?
They are both trussed arches
Describe the abutments of the Bayonne Bridge from the scientific perspective, as discussed in lecture.
They are unnecessary steel skeletons
Railroads carry locomotives that can be extremely heavy. Name a new material that structural artists used in the 1800's to design bridges for these loads? Give an example of a railroad bridge, name the designer, and classify the bridge type (e.g. suspension bridge).
They began using wire rope in the 1800s to design railroad bridges. The Niagara Bridge was a railroad bridge designed by Roebling. It is a suspension bridge that used this wire rope.
Why was the deck of the Bayonne Bridge raised?
They raised the deck so larger, taller ships could pass under the bridge
In suspension bridges, what are two ways to mitigate the effects of flutter while maintaining thin decks?
Two ways to mitigate the effects of flutter w/ thin decks: Retrofits: stays and deep truss Retrofits: stays and air foils
Explain the relationship between wire, strand, and cable.
Wires → strands → cables
