Unit II Dams, Bridges(1)

8/12/2019 Unit II Dams, Bridges(1)

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UNIT II

DAMS AND BRIDGES

Times New Roman


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DAMS

Dam : It is a defined as an impervious barrier or

an obstruction constructed across a natural

stream or river.

Purpose:

To hold up the water on one side of it (Upstream

side)

The other side is known as downstream side.


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CLASSIFICATION

1. Rigid Dams

(a) Solid Gravity dams

(b) Arch dams

(c) Buttress dams

(d) Timber and steel dams

2. Non Rigid dams

(a) Earth dams(b) Rock fill dams


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SOLID GRAVITY DAMS


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SOLID GRAVITY DAM

Its own weight resists the external forces

More durable and has maximum rigidity

Requires less maintenance compared to other

types.

This type of dam is constructed of concrete or

masonry.


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ARCH DAM


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ARCH DAMS

Arch DamEl Atazar DamMadrid,Spain


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TYPES OF ARCH DAMS

Constant radius arch dams- commonly have a

vertical upstream face with a constant radius of

curvature

Variable radius dams - have upstream anddownstream curves of systematically decreasing

radii with depth below the crest.


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BUTTRESS DAMS

Buttress Dam Is a

gravity dam reinforced

by structural supports

Buttress - a support thattransmits a force from a

roof or wall to another

supporting structure


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BUTTRESS DAMS

It has relatively thin sections when compared to

a gravity dam.

Consists of sloping section, buttresses and base

slab.

Sloping membrane first takes the water load and

transfers it to the buttresses which are at specific

intervals.

The buttresses inturn transfer the load to the base

slab which forms the foundation part of the dam.


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EARTH DAMS

Earth dams are also calledearthen, rolled-earth or

simply earth-fill dam

It may contain a watertight

concrete or clay core or

sometimes with a hydraulic

fill to produce a watertight

core and a drain layer tocollect seep water.


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EARTH DAMS


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FAILURES OF EARTH DAM


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ROCK FILL DAMS


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ROCK FILL DAMS

Made of loose rocks and boulders piled in theriver bed.

A slab of reinforced concrete is often laid on the

upstream face to make it water tight.

These are more than earth dams and less stable

than gravity dams.

These dams consists of dry rubble stone

masonry on upstream side and loose rock fill on

downstream side.


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CULVERTS

A Culvert is a drain or water course totallyenclosed and usually carried under a road or a

railway track.

Types

(a) Box culvert

(b) Pipe culvert

(c) Arch culvert


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BOX CULVERT

Consists of one or more

square or rectangular

openings made of RCC

or masonry.

Cheapest alternative for

pipe culvert.


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PIPE CULVERT

Most economical forsmall drainage

crossings.

These are preferred fordiameters less than

1.8m.

The pipes may be of CIor RCC.


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PIPE CULVERT


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ARCH CULVERT

It is constructed onbrick or stone or

concrete walls having

short spans of 2 to 3m.


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BRIDGES

It is a structure providing passage over an obstaclesuch as a valley, road, railway canal, river

without closing the way beneath.

The required passage may be for road, railway,canal, pipe line, cycle track or pedestrians.


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Types of bridges

Deck Bridge

Arch bridge

Slab Bridge

Suspension bridge Steel Bridge

Steel Truss bridge

steel Girder bridges


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DECK BRIDGE

In deck bridge, the platform of the bridge

carries the

communication route,which is supported at

the superstructure.

Plat form


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ARCH BRIDGE


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ARCH BRIDGE

These bridges have pleasing appearance.

Can be economically adopted for 250 m span

length.

No bending at any part of the bridge.

Vibrations due to impact forces is minimum.


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CLASSIFICATION OF ARCH BRIDGE


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SLAB BRIDGE


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SUSPENSION BRIDGE


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SUSPENSION BRIDGE


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SUSPENSION BRIDGE

Superstructure of suspension consists of twosets of cables over the towers carrying the bridge

floor by means of suspenders.

It is best suited for light traffic and large spansexceeding 600 m.

Flexible and hence vertical oscillations will be

more than other bridges.


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STEEL TRUSS BRIDGE


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STEEL TRUSS BRIDGE

It is provided for long railway passages.

They are less affected by wind forces.

It is easy to erect, since components of bridges

are light in weight.


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STEEL GIRDER BRIDGE


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References

Basic Civil and Mechanical Engineering

K.V. NatarajanBasic Civil and Mechanical EngineeringShanmugam

and Palanichamy.

Prepared by

A.R. Pradeep Kumar,

Associate Professor Mechanical,

DCE

Documents

Unit II Dams, Bridges(1)