Statics: Bridges

Suspension Bridge

World's Longest Suspension Bridge:

Akashi Kaikyō Bridge, Japan
AKA "Pearl Bridge"
1,991 meters = 1.24 miles
built to withstand typhoons, tsunamis, earthquakes, and corrosive salt-water environment

Before the bridge, ferries were used to transport people across the Seto Inland Sea.

Siun Maru disaster

JNR (Japanese National Railway ferry "Uko Maru" collided with the Sium Maru ferry.
Accident attributed to thick fog, and lack of radar.
168 people killed including 100 elementary and junior high school students who were on a field trip.

Akashi bridge project was started to replace the dangerous ferry route.
10 years to build to build the bridge: 1988-1998

https://www.youtube.com/watch?v=N9fbRcRJY34

Bridge: Big-Bigger-Biggest, 2008

(Movie copyright: National Geographic, English subtitle prepared by ACUD.VN)

https://www.youtube.com/watch?v=lJIknkN7_84

https://www.youtube.com/watch?v=mjBuBEQmQzw

Leap 1: Material

Stone arches (max 30m span, larger bridges cannot hold up their own weight)
Cast Iron (too brittle)
First Iron bridge built in 1779 "Iron Bridge"
iron corrodes/rusts, needs maintenance.

Leap 2: the suspension bridge
Rope bridges → iron chains→Cables
Need anchor

Leap 3: strong chains
Chains - only as strong as their weakest link
1845 - 79 people standing on a bridge watching a clown pulled in barrel by geese drown
Niagra Bridge

Leap 4: building underwater
Brooklyn Bridge: 140,000 vehicles per day
Sludge & silt→bedrock
Shallow water: People working in wood casons with air locks
Deeper water: steel cason

Leap 5: taller towers
Golden Gate: Too much traffic for ferries
Ideal curve for a bridge - https://en.wikipedia.org/wiki/Catenary
Increase length = increase height to maintain ideal curve
Towers need to be strong enough to support cables, and ductile to bend when needed

Leap 6: wind
Longer decks = more twisting and bending = more susceptible to wind
Open Lattice box structure
open - allows wind to flow through bridge (rather than trying to divert wind)
box - keeps it from bending.

Leap 7: earth quake
Dampener Pendulums
Flexible materials

Bridge
Big-Bigger-Biggest
2008
https://www.youtube.com/watch?v=ZCrwIyfnyY0
Megastructure Longest Suspension Bridge In The World Construction Documentary