Havenyou ever wondered how people build bridges? How do you start? Do younbuild from the bottom up, or from the top down? How do you start tonreach from side to side over treacherous waters or a deep chasm?
n
n
n
n
nThenNiagara Falls Suspension Bridge is an early example of a bridge thatnallowed pedestrians, carriages, and trains to cross a wide river—asna matter of fact, it is the world’s first working railway suspensionnbridge. And that first step—the laying of the first line across thenwide and turbulent Niagara River—was accomplished by flying a kite!nn
n
n
n
n
n
nThenbuilders were stumped because the water was so turbulent that thenrapids were called Whirlpool Gorge. They didn’t think a boat couldntake the first wire across the river to start the bridge. Someonensuggested shooting a rocket attached to a wire, or some sort ofnbombshell with a wire, shot out of a cannon. But one many suggestednoffering a cash prize to the first child who could fly a kite overnthe gorge. n
n
n
n
n
n
nAn15-year-old boy named Homan Walsh won the prize (either $5 orn$10—accounts vary) by flying a kite from the Canadian side of thengorge. Eventually, when the winds subsided, his kite descended andngot caught in a tree on the American side. The day after thisncontest-winning flight, a stronger line was attached to the kitenstring; a rope followed, and then a cable made of wire.
n
n
n
n
n
nNext,nthe builders created a temporary suspension bridge across the NiagaranRiver. They used that temporary bridge to build a better, stronger,npermanent bridge.
n
n
n
n
n
n
I’ve always wondered how bridge builders create those supportive towers innwater. I found out that, in the olden days (such as the days of thenRoman Empire), huge boulders were piled up in the water, and thenbridge was built on and secured to the boulder piles. Later, buildersnwould lower a caisson, which is a huge cylinder made of steel andnconcrete, into the water and onto the river-, lake-, or seabed. Thenwater was then pumped out of the caisson. At this point, the caissonnbecame a sort of circular dam that kept water away from workers andnequipment. Since the 1930s, bridge builders generally float enormousnmetal caissons to the designated spot and then sink the caissons byngradually filling them with concrete and water. Divers are on hand tonmake sure that the sinking caissons settle on the right bit ofnground. n
I’ve always wondered how bridge builders create those supportive towers innwater. I found out that, in the olden days (such as the days of thenRoman Empire), huge boulders were piled up in the water, and thenbridge was built on and secured to the boulder piles. Later, buildersnwould lower a caisson, which is a huge cylinder made of steel andnconcrete, into the water and onto the river-, lake-, or seabed. Thenwater was then pumped out of the caisson. At this point, the caissonnbecame a sort of circular dam that kept water away from workers andnequipment. Since the 1930s, bridge builders generally float enormousnmetal caissons to the designated spot and then sink the caissons byngradually filling them with concrete and water. Divers are on hand tonmake sure that the sinking caissons settle on the right bit ofnground. nn
n
n
n
n
nTonlearn more about building bridges, check out the Worsley School Building Bridges page. Also, check out the Official Bridge Day website.
n
- n
-
nAlso,n this earlier postn deals with a bridge disaster,
n
-
nthisn earlier post discusses cantilever bridges, and
n
-
nthis earlier postn links to some fun bridge experiments.
n
n
n
n
n
n
n
n
n
nAlsonon this date:
n
n
n
n
n
n
Architect Christopher Wren’s birthday
Architect Christopher Wren’s birthday n
n
n
n
n
n
n
n
n
n
n
n
nBaseball great Mickey Mantle’s birthday
nn
n
n
n
n
n
n
n