BRIDGE BUILDING · Suspension Bridge – Modern Suspension Bridges ! Modern Suspension bridges have an M-Shaped pattern and are the most impressive type of bridge with their long

BRIDGE BUILDING

Bridge Facts l  Can you name the longest bridge in the world?

The Akashi-Kaikyo Bridge

Bridge Facts l  Comparing the various bridges…..

Bridge Facts (cont.)

l  Can you name the longest bridge in America?

The Lake Pontchartrain Causeway Bridge (23.9 miles) (Louisiana)

Bridge Facts (cont.) l  What is the oldest standing stone bridge in the world?

The Zhaozhou Bridge( China)

Bridge Facts (cont.) l  What is the highest suspension bridge in the world?

The Royal Gorge Bridge above the Arkansas River Click here to cross the bridge!

Bridge Facts (cont.) l  New York City Bridges!!

Famous Bridges of New York!!

Bridge Facts (cont.) l  Different types of Bridges!!

Tower Bridge - London!!

Cable and Wooden Planck Bridge

– New Zealand!! Tsurimi Tsubasa Bridge

- Japan!!

Definition

l  What is a bridge? Ø A structure built in order to allow people or vehicles to

cross a river or a valley etc. Bridges are structures which carry people and vehicles across natural or man-made obstacles.

l  When was the first bridge built?

Ø Prehistoric time

Materials Used

l  What materials are used in bridge construction? Ø Stone Ø Wood Ø Grass Ø Steel Ø Concrete

Types of Bridges

Ø Do you know any type of bridges??

Ø Where did you see it??

Ø What engineering aspects did you notice??

Types of Bridges

Ø  Beam Ø  Truss

Ø  Arch

Ø  Suspension Ø Modern Suspension Ø Cable-Stayed

Beam Bridge

l  Beam bridges are the simplest and least expensive type of bridges to build!!

l  A horizontal beam supported at its ends comprises the structure of a beam bridge (span a distance of approximately 200 feet).

l  Highway overpasses, flyovers or walkways

Beam Bridge - (Truss Bridge)

l  A truss bridge is built by connecting straight elements with the help of pin joints (span a distance of approximately 1200 feet)

l  Deck truss railroad bridge that extends over the Erie Canal is one of the many famous truss bridges.

Arch Bridge

l  Arch bridges are the easiest type of bridges to recognize!! l  An arch-shaped structure which has supports at both its ends.

The weight of an arch-shaped bridge is forced into the supports at either end (span a distance of approximately 800 feet).

Suspension Bridge – Modern Suspension Bridges l  Modern Suspension bridges have an M-Shaped pattern and

are the most impressive type of bridge with their long main span and beauty!!

l  A bridge falling under this category is suspended from cables. The suspension cables are anchored at each end of the bridge (span a distance of approximately 2000 to 7000 feet).

l  Cable-Stayed Bridges have an A-shaped pattern and use less cable and are the BRIDGES OF CHOICE!!

l  The forces – Compressive and Tensile are same for both suspension bridges (span a distance of approximately 500 to 3000 feet).

Suspension Bridge – Cable-Stayed Bridges

The Tower Bridge in London is three types of bridges in one.

•  The shore-to-tower spans are suspension bridges

•  The pedestrian walkways are truss (beam) bridges

•  The center span is movable to allow tall ships to pass.

Guess the types of bridges embedded in this one bridge!!!

Forces acting on Beam Bridges and Truss Bridges

Two important forces dealt by all bridges: •  Compression is a force that acts to compress or shorten

the thing it is acting on. •  Tension is a force that acts to expand or lengthen the

thing it is acting on.

When something pushes down on the beam, the beam bends. Its top edge is pushed together, and its bottom edge is pulled apart.

Forces acting on Arch Bridges

The arch is squeezed together, and this squeezing force is carried outward along the curve to the supports at each end. The supports, called abutments, push back on the arch and prevent the ends of the arch from spreading apart.

Forces acting on Suspension Bridges – Modern Suspension Bridges

In all suspension bridges, the roadway hangs from massive steel cables, which are draped over two towers and secured into solid concrete blocks, called anchorages, on both ends of the bridge. The cars push down on the roadway, but because the roadway is suspended, the cables transfer the load into compression in the two towers. The two towers support most of the bridge's weight.

Forces acting on Suspension Bridges – Cable- Stayed Bridges

Cables are anchored directly to the towers and eliminate the need for an anchorage system. The same tensile and compressive forces are seen in a cable-stayed bridge as they are in a modern suspension bridge.

ü Designing the various load combinations and determining the required size of the bridge. ü Creating models of beam, arch and suspension bridges and apply forces to understand how they disperse the loads. ü Building a model Truss Bridge using straws and popsicle sticks. ü Exploring the Bridge building software and designing new bridges. ü Bridge Building Competition.

Exploring Activities

Bridge Challenge #1

A growing community needs a bridge, to connect the city and a major highway crossing a river. They're very picky about what they want! Help them by testing your engineering skills and match the right bridge to the location shown in the figure below!!

Multi-lane bridge for commuters and tourists

Special Notes: "I want a one-of-a-kind bridge that will span our beautiful river and welcome visitors from all over the world to our thriving city. Make sure the new bridge leaves enough room for sailboats on the river. Please don't build a bridge that looks like the Golden Gate Bridge in San Francisco or the Brooklyn Bridge in New York." -- Mayor of Craggy Rock

Span: 2,000 feet Crossing: River Connects: City and major

highway Source: http://www.pbs.org/wgbh/buildingbig/bridge/challenge/

Bridge Challenge #1

ü  Beam Bridge

ü  Suspension Bridge

ü  Arch Bridge

ü  Draw Bridge



highway

Source: http://www.pbs.org/wgbh/buildingbig/bridge/challenge/

Bridge Challenge #1

ü  Draw Bridge



highway

But, there is a problem - the residents of Craggy Rock spoke out against the new drawbridge. "It's ugly," one angry resident said, "and there's always traffic on the bridge. They open it for boats, but what about us? We have to get to work, too!"


Bridge Challenge #1 Multi-lane bridge for commuters and tourists


highway

The mayor is begging you to build a new bridge. The local steelworkers are on strike, so she advises you to build a bridge with as little steel as possible.

ü  Cable-stayed Bridge

ü  Cantilever Bridge

ü  Combination – Arch & Beam Bridge


Bridge Challenge #1 Multi-lane bridge for commuters and tourists


highway

ü  Cable-stayed Bridge

These have become one of the most popular bridge types in recent years. The roadway hangs from cables like a suspension bridge, forming a unique "A" shape. The mayor is happy because the bridge is made mostly of concrete, a relatively cheap material. The residents are thrilled because ships can pass beneath the bridge without causing traffic jams!


Bridge Challenge #2

A growing community needs a bridge, to connect the bike paths in East and West Craggy Rock. They're very picky about what they want! Help them by testing your engineering skills and match the right bridge to the location shown in the figure below!!

A bridge for rollerbladers and bikers

Special Notes: "We're tired of getting bumped off the road by angry drivers! We want a simple bridge -- one that will connect the bike paths in East and West Craggy Rock over the city stream. We don't have much money, so we're not asking for much. We just want to get to work every day without risking our lives!" -- Craggy Rock Bike-n-Blade Coalition Span: 100 feet

Crossing: Stream Connects: Two bike paths


ü  Beam Bridge


ü  Arch Bridge

ü  Draw Bridge

Span: 100 feet Crossing: Stream Connects: Two bike paths

Bridge Challenge #2 A bridge for rollerbladers and bikers


ü  Beam Bridge

This is an excellent spot for a beam bridge!! Beam bridges typically span up to 250 feet, and they're also the cheapest and easiest bridges to build.

Congrats -- you've just made a lot of rollerbladers and bikers very happy!




When it rains, the city stream rises. A really strong storm could cause flash floods, turning the stream into a raging river. Piles of rocks and a wall of gooey mud could push on the piers of the concrete beam bridge and cause it to topple. Luckily, you can fix it before that happens!



ü  Beam Bridge However, there is a problem…….


How will you build a new, flood-proof bridge?

ü  Build deeper piers

ü  Build higher deck

ü  Use stronger material




ü  Deeper piers Great Idea!!

One of the best ways to strengthen a bridge in a flood zone is to set the piers deeper into the ground. The deeper the piers are lodged into the ground, the harder it is to knock them over. The next time floodwaters pound on the piers of your new bridge, it probably won't budge!




Bridge Challenge #3

A growing community needs a bridge, to connect the two halves of the city across the harbor entrance. They're very picky about what they want! Help them by testing your engineering skills and match the right bridge to the location shown in the figure below!!

A highway bridge across a busy shipping port

Special Notes: "Our records indicate that more than 500 ships pass through Craggy Rock Harbor each day. Please build a bridge that does not block the flow of water traffic. We do not want angry sailors or congestion of any kind in our harbor. Thank you." -- The United States Coast Guard Span: 5000feet

Crossing: Ocean bay Connects: Island and mainland


ü  Beam Bridge


ü  Arch Bridge

ü  Draw Bridge

Bridge Challenge #3

Span: 5000feet Crossing: Ocean bay Connects: Island and mainland




This is an ideal location for a suspension bridge. Suspension bridges, like the Akashi Kaikyo Bridge in Japan, can span great distances and still leave room for passing ships and boats. The U.S. Coast Guard is thrilled with your selection!

Bridge Challenge #3




Your new bridge is moving up and down a lot in the wind! This isn't a big problem under normal conditions, but what if a hurricane were to blow through town? It could cause the bridge to move too much, or even twist so violently that it would snap in half!

However, there is a problem……. ü  Suspension Bridge

Bridge Challenge #3



How can you strengthen the bridge to resist strong winds?

ü  Stiffen the deck with an open TRUSS?

ü  Stiffen the deck with a solid steel GIRDER?

ü  Make the bridge NARROWER?

Bridge Challenge #3




ü  Open Truss Great Idea!!

This is a great solution! By adding an open truss beneath the deck of the bridge, you've designed a structure that is less likely to move up and down a lot on a gusty day, because the wind will blow right through it! Since the Tacoma Narrows Bridge disaster in 1940, many major suspension bridges have been built with a stiffening truss.

A highway bridge across a busy shipping port Bridge Challenge #3



Conclusion

l  Based on the above activities different types of bridges can be built.

l  Different types of structures and materials can be experimented with in order to increase the strength of the bridge.

l  Efficiency of the bridge can also be calculated.

Documents

BRIDGE BUILDING · Suspension Bridge – Modern Suspension Bridges ! Modern Suspension bridges have an M-Shaped pattern and are the most impressive type of bridge with their long