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Forces Acting on DamsForces Acting on Dams

To design a dam, various forces must beTo design a dam, various forces must beconsidered to insure the safety of theconsidered to insure the safety of the

dam. The most important forces aredam. The most important forces are::

1.1. Weight of damWeight of dam2.2. Water PressureWater Pressure

3.3. p!iftp!ift".". Wave pressureWave pressure#.#. $arth%ua&e forces$arth%ua&e forces

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' Weight of DamWeight of Dam

The (eight of the dam is ca!cu!ated asThe (eight of the dam is ca!cu!ated as

fo!!o(s)fo!!o(s)

WhereWhere **mmis the speci+c (eight of theis the speci+c (eight of the

dams materia!.dams materia!.

xVolumeWm

=

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' Water PressureWater Pressure

Water pressure acts perpendicu!ar to theWater pressure acts perpendicu!ar to the

surface of the dam and is ca!cu!ated persurface of the dam and is ca!cu!ated per

unit (idth as fo!!o(s)unit (idth as fo!!o(s)

WhereWhere **( is the speci+c (eight of (ater and( is the speci+c (eight of (ater and

h is the height of (ater.h is the height of (ater.

2

2

1 hPw

= Pw

h/3

h

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' p!iftp!ift

Dams are sub-ected to up!ift forceDams are sub-ected to up!ift forceunder its base. p!ift acts up(ard.under its base. p!ift acts up(ard.

Where is the (idth of the base of theWhere is the (idth of the base of thedam.dam.

hBU w21=

h

U

B

B/3

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' Wave PressureWave Pressure

The upper part of the dam /above theThe upper part of the dam /above the

(ater !eve!0 is sub-ected to the(ater !eve!0 is sub-ected to the

impact of (aves. The maimumimpact of (aves. The maimum

(ave pressure per unit (idth is)(ave pressure per unit (idth is)

Where hWhere h((is the (ave height.is the (ave height.

vwv hP 4.2=

Pw

0.375hw h

w

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$arth%ua&e Forces$arth%ua&e Forces

Dams are sub-ected to vibration duringDams are sub-ected to vibration during

earth%ua&es. ibration aects both theearth%ua&es. ibration aects both the

body of the dam and the (ater in thebody of the dam and the (ater in thereservoir behind the dam. ibrationreservoir behind the dam. ibration

forces are function of both the intensityforces are function of both the intensity

/4echter 5ca!e0 and its duration. The/4echter 5ca!e0 and its duration. The

most danger eect occurs (hen themost danger eect occurs (hen thevibration is perpendicu!ar to the face ofvibration is perpendicu!ar to the face of

the dam.the dam.

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' ody Forces)ody Forces)

ody force acts hori6onta!!y at theody force acts hori6onta!!y at thecenter of gravity and is ca!cu!ated as)center of gravity and is ca!cu!ated as)

WhereWhere 77is the earth%ua&e coe8cientis the earth%ua&e coe8cientand W is the (eight of the dam. 9sand W is the (eight of the dam. 9sta&en :.2 for practica! reasons.ta&en :.2 for practica! reasons.

WPem =

W1

0.1 W1

W2

0.1 W2

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' Water Force)Water Force)Water vibration produces a force onWater vibration produces a force on

the dam acting hori6onta!!y;the dam acting hori6onta!!y;

Where

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' $amp!e)$amp!e)

2.# t?m33,, **((>1 t?m>1 t?m33, h( > 1.# m, h( > 1.# m

6m

24m

30m

10m

33m

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' 1. Weight of (ater1. Weight of (ater

WW11>2.# @ @ ": > :: t>2.# @ @ ": > :: t

WW22>2.# @:.#@1=@3:>2.# @:.#@1=@3:

> B# t> B# t

' 2. Water Pressure2. Water Pressure

P > :.# @ 1.: @ /330P > :.# @ 1.: @ /33022

> #"".# t> #"".# t

(1 (2

P

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' 3. p!ift3. p!ift

> :.# @ 1.: @ 33 @ 2" > :.# @ 1.: @ 33 @ 2" > 3C t> 3C t

' ". Wave Pressure". Wave PressurePP((> 2." @ 1.: @ 1.#> 2." @ 1.: @ 1.#

> 3. t> 3. t

P(

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' #. $arth%ua&e Forces#. $arth%ua&e Forces

a. ody Forcesa. ody Forces

PPem1em1> :.1 @ ::> :.1 @ ::

> : t> : t

PPem2em2> :.1 @ B#> :.1 @ B#> B.# t> B.# t

b. (ater Forceb. (ater Force

PPe(e(>/2?30@:.=2@:.1@/3302>/2?30@:.=2@:.1@/3302

> #C.## t> #C.## t

Pem1

Pem2

Pe(