By Justin Miller

8/9/2019 By Justin Miller

1/12


2/12


3/12


4/12


5/12


6/12


7/12

Why We Need Bridges

Bridges make it possible to cross from one shoreof a river to another. In earlier times bridgesallowed trade between farmers and the

movement of goods across a natural divide. Early man often placed stepping stones in the

narrow sections of small streams as a way to getto the other side. It is easy to see how a bridge

might develop using stepping-stones as a basefor logs or planks. The earliest bridge wasprobably a toppled tree that had fallen across anearby stream.


8/12

Are Bridges Always over Water?

No they can be over other roads, railways,

and deep gulley's. They are not only for cars

and people. Wooden trestle bridges wereessential to the passage of the railway

through the mountains in western Canada.


9/12

HowA suspension Bridge Is Made

This type of bridge has cables suspended between towers plusvertical suspender cables that carry the weight of the deck below,upon which traffic crosses. This arrangement allows the deck to belevel or to arc upward for additional clearance. Like other suspensionbridge type this type often is constructed without false work.

The suspension cables must be anchored at each end of the bridge,since any load applied to the bridge is transformed into a tension inthese main cables. The main cables continue beyond the pillars todeck-level supports and further continue to connections withanchors in the ground. The roadway is supported by verticalsuspender cables or rods called hangers. In some circumstances thetowers may sit on a bluff or canyon edge where the road mayproceed directly to the main span otherwise the bridge will usuallyhave two smaller spans, running between either pair of pillars andthe highway which may be supported by suspender cables or mayuse a truss bridge to make this connection. In the latter case therewill be very little arc in the outboard.


10/12

Cantilever Bridge

Cantilever bridges are built with many

materials in different ways. Others just have

arms and a roadway or arms a roadway andcables that work like a cable stayed bridge.

Cantilever bridges are built in a way similar to

beam and arch bridges depending on how the

bridge is designed.


11/12

Why We Have Interstates

We need interstates so we can make it places

that we normally cant. We also need them so

we can make it to places quicker instead ofgoing in main streets and driving 25 to 30

mph. The Interstate System currently has

approximately 210,000 lane miles of

pavement. The interstate system also has55,000 bridges on them.


12/12

Facts about Interstates

By Justin Miller

Documents

Transcript of By Justin Miller