Bridge is a structure which covers a gap.

A bridge that span physical obstacles

such as river ,valley or road is structure

built.

The first bridges consisted of fallen

logs over rivers.

Designs of bridges vary depending on

the function of the bridge

Arch bridges are one of the oldest types

of bridges and have been around for

thousands of years. Arch bridges have

great natural strength.

They were originally built of stone or brick

but these days are built of reinforced

concrete or steel.

Arch bridges are always under

compression.

The tension in an arch isn’t considered

important.

Consequently, materials have that use at

arch bridges, weak tension.

Instead of pushing straight down, the

load of an arch bridge is carried

outward along the curve of the arch to

the supports at each end. The weight is

transferred to the supports at either end.

These supports, called abutments, carry

the load and keep the ends of the

bridge from spreading out.

The load at the top of the key stone makes each stone on the arch of the bridge press on the one next to it.

This happens until the push is applied to the end supports or abutments, which are embedded in the ground.

The design of the arch, the semicircle, naturally diverts the weight from the bridge deck to the abutments.

When the load is divided between a

series of smaller arches.The thrust at

the internal supports balance each

other and thrust is reduced .

A beam or "girder" bridge is the simplest

kind of bridge and two parallel beams

supported by piers of bridge.

Span can be supported by trestle.

Pratt warren

The beam weight pushes straight down

on the piers.

They have bigger internal forces

compared to arch bridges because of

trying to bend.

You can use wooden, reinforced

concrete, prestressed-concrete or steel

as materials.

Large span structures have poor

aesthetic appearance of the truss bridge

but for moderate spans its best to

provide at simple and regular structures.

When loads are applied to a truss at the joints, forces are transmitted only in the direction of each of its member.

Other bridge types have high fabrication cost compared to truss bridges.

Trusses have a high strength to weight ratio and consequently are used in many structures.

Cantilever bridge that built using

cantilever is a bridge .

A cantilever bridge is made from beams

supported on one side only.

The bridge formed with two design

trusses that join in the center by a

connecting member as pin-connected .

The diagram shows a cantilever bridge

supporting a load .

Wooden cantilever bridges were popular in Asia.

The steel cantilever truss bridge was huge breakthrough.

The most famous example of cantilever bridge is the Forth Railway Bridge in Scotland which was the longest span in the world until 1919 .

After The Quebec Bridge was built in Canada.

Native Suspension Bridge

One of the First Discovered in Asia

The first use of suspension

bridge extends to

prehistoric times.

Ancient people used

some plants as like vine

and bamboo for create

suspension bridge.

The first suspension bridge

was built by Chinese people with chains and ropes.

History of Suspension Bridges

Bosphorus Bridge

Undoubtedly , Steel

cable are the most

important factor in the

development of the

suspension bridge.

.

The First modern steel cable

was created by Albert Rop in

1834.

Today, suspension

bridge cables are

made of thousands

of individual steel

wires bound tightly

together.

Steel is strong under

tension, and an ideal material for cables.

A single steel wire, only 0.1 inch thick, can support

load over half a ton without breaking.

The suspension bridge is most preferred bridge to overcome

the long spans.

Suspension bridge

can provide to

overcome the long

spans, but there are

serious drawbacks

They are very flexible

,and traffic load can

lead to a large

collapse.

Thus, a support

beam or a box

beam is added to

help the cable.

Golden Gate Bridge

The Akashi Kaikyo Suspension Bridge is the longest

suspension bridge in the world

Mostly everyone chooses suspension bridge in long

span because Cable wires are cheaper and more

durable than steel beams.

The suspension bridge's carrier system consists of

the following elements:

1. Deck

2. Suspension

cables

3. Main cables

4. Towers

5. The anchor

blocks

• Tower carries the main cables.

• Anchors provides remain to tense of main cable.

• Suspension cables transfer load of deck to main cable .

• Towers can be made from steel or reinforced concrete.

• Usually , deck made from shaped steel cage sytems.

.

How Suspension Bridges Work

The main cables are tense with vertical cables that

attach to the deck.

These cables support the deck of the bridge,

transferring the weight to the towers at the end.

The main cables continue past the tower, and they are anchored past the far ends of the bridge.

They are carefully balanced so that the force pulling

inward on the towers is equal to the force pulling outward.

As a result, the weight pulls directly down into the

base of the tower.

Cable-stayed bridges are a type of suspension bridge.

Cable-stayed

bridges have tall

towers like

suspension bridges,

but in a cable-

stayed bridge, the

roadway is attached

directly to the towers

by a series of

diagonal cables.

A cable-stayed bridge is constructed in much

the same way as a suspension bridge is, but

without the main cables.

Advantages a cable-stayed bridge has

over a standard suspension bridge include

speed of construction and lower cost, since

anchorages are not necessary.

The cable-stayed bridge

is optimal for spans longer

than cantilever bridges

and, shorter then

suspension bridges.

Cable-stayed designs are

used for intermediate-

length spans.

There are no main

cables, as with

suspension bridges,

making cable repair or

replacement simpler.

• There are two major classes of cable-

stayed bridges: harp and fan.

Harp Design Fan Design

Harp Design Cable-Stayed Bridges

In the harp or parallel design, the cables are nearly

parallel.

Fan Design Cable-Stayed Bridges

In the fan design, the cables all connect to or pass

over the top of the towers.