water tanks lecture 4

7/23/2019 Water Tanks Lecture 4

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Lecture 4

January 30, 2006


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Sudhir K. Jain, IITKan ur

E-Course on Seisic !esi"n o# Tan$s% January 2006 Lecture 4 % S&ide 2

In this &ecture

', I, Sa%" and ( )a&ues #or tan$s


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*ase shear coe+cient

Seisic #orce /h 1 /his ase shear coe+cient

Zone

Dependson

severity ofground

motion

Structuralcharacteristics

Depends on timeperiod and damping

2

Z

RI

gSa=hA

Designphilosoph

y


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*ase shear coe+cient

Ipu&si)e ase shear coe+cient /hi '%2 1 I%( 1 Sa%"i

Con)ecti)e ase shear coe+cient /hc '%2 1 I%( 1 Sa%"c ote, ( has een used in /hias e&& as /hc

'one #actor, ' /s per Ta&e 2 o# IS 7893:art7;2002

I, (, Sa%"iand Sa%"ci&& e discussed here


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Sa%"iand Sa%"c

Sa%"iis a)era"e response acce&eration #oripu&si)e ode !epends on tie period and dapin" o#

ipu&si)e ode

Sa%"cis a)era"e response acce&eration

#or con)ecti)e ode !epends on tie period and dapin" o#

con)ecti)e ode


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Sa%"iand Sa%"c

?odi>cations are; The risin" portion in short period ran"e #ro 0 to

0.7 sec has een ade constant Very stif structures have time period less than 0.1 sec There may be modeling errors; actual time period may

be slightly higher As the structure gets slightly damaged, its naturalperiod elongates

Ductility does not help in reducing response o very stifstructures

ence, rising portion in the range 0 to 0.1 sec is usually

disallo!ed by the codes. Spectra is e1tended eyond 4 sec

"ince convective time period may be greater than # sec. $eyond # sec, 1%T variation is retained


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Sa%"iand Sa%"c

Spectra o# IS 7893 :art 7;2002?odi>edspectra


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!apin"

!apin" #or ipu&si)e ode 5@ o# critica& #or (C tan$s

2@ o# critica& #or stee& tan$s

These are $ept in &ine ith IS 7893:art 7 lause /.+.(.1 o " 1+23art 14 suggests *)

damping or 5 and () damping or steel buildings

Boe)er, I*C 2003 su""ests 5@ dapin" #ora&& tan$s

t suggests *) damping or all types o buildings also


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!apin"

!apin" #or con)ecti)e ode 0.5@ o# critica& #or a&& types o# tan$s Con)ecti)e ode dapin" does not depend on

ateria& o# tan$ or type o# &iuid stored

In Ta&e 3 o# IS 7893:art 7;2002 ?u&tip&yin" #actor #or 0.5@ dapin" is not "i)en a&ues are "i)en #or 0@ and 2@ dapin" Linear interpo&ation sha&& not e done

?u&tip&yin" #actor 7.=5, #or 0.5@ dapin" In Eurocode 8 this u&tip&yin" #actor is 7.6=3 In /CI 350.3, this #actor is 7.5


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Iportance #actor, I

Iportance #actor, I #or tan$s is "i)en inTa&e 7 o# the Duide&ine This Ta&e is reproduced here

Type of liquid storage tank ITanks used for storing drinking water, non-volatile material, low inammable petrochemicalsetc and intended for emergency services such as!re !ghting services Tanks of post earthquake

importance

"#

$ll other tanks with no risk to life and withnegligible consequences to environment, societyand economy

"%

&'T() *alues of importance factor, + given in +S "./0art 12

may be used where appropriate


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Iportance #actor, I


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(esponse reduction #actor, (

There are critica& diAerences eteenui&din" #raesand non-ui&din" #raes

Internationa& codes c&ear&y diAerentiateeteen these to types o# #raes *ui&din" #raes ha)e ri"id diaphra"s at oor

&e)e&s 6rames o staging do not have rigid diaphragms

In ui&din"s, seisic ei"ht is distriuted

a&on" the hei"ht at each oor &e)e& n elevated tan9s, almost entire seismic !eight is

concentrated at the top These are inverted pendulum type structures


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In this >"ure, cur)ature ducti&ity is p&ottedas a #unction o# &on"itudina& rein#orceent

These resu&ts are #or inner !i to outer !o

diaeter ratio o# 0.94. I# ratio o# a1ia& &oad : to u&tiate &oad #c$./"

is 0.7 then, cur)ature ducti&ity is aout 9 #or/st%/" 0.02

This )a&ue reduces to 3 #or :% #Mc./" o# 0.25

o, &et us see soe resu&ts on eAect o#sha#t thic$ness


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E-Course on Seisic !esi"n o# Tan$s% January 2006 Lecture 4 % S&ide 3=


Soe use#u& in#oration on (C sha#t is"i)en in /CI 3=7-98 A 2/1F+ , 1+, < -uide or the analysis, design ,

and construction o concreteFpedestal !ater To!ers>,American oncrete nstitute, 6armington ill, &, "A.

It e1c&usi)e&y dea&s ith tan$s on (C sha#t It su""ests sae desi"n #orces as I*C 2003 It "i)es in#oration on;

minimum steel construction tolerances saety against buc9ling

shear design etc.


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In the ao)e to docuents, #o&&oin"internationa& codes are re)ieed andcopared; I*C 2000 no, I*C 2003

/CI 350.3 /CI 3=7 // !-770 and // !-775 // !-700 and // !-703

/:I 650 and /:I 620 Eurocode 8 'SEE recoendations


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o e $no ', I, ( and Sa%" #or tan$s ne can no otain ase shear

coe+cient #or ipu&si)e and con)ecti)eodes /n e1ap&e #o&&os.


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E1ap&e

E1ap&e; /n e&e)ated ater tan$ has (C #raesta"in" detai&ed #or ducti&ity as per IS; 73920 andis &ocated in seisic Fone I. Site o# the tan$ hasso#t soi&. Ipu&si)e and con)ecti)e tie periodsare 7.2 sec and 4.0 sec, respecti)e&y. tain aseshear coe+cient #or ipu&si)e and con)ecti)eode.

So&ution;

'one; I

' 0.24 6rom Table ( o " 1+2 3A5T 4H(00(,

I 7.5 6rom Table 1 o the -uideline ( 2.5 #or (C #rae ith "ood ducti&ity

S?(


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E1ap&e on /hiand /hc

Ipu&si)e tie period, Ti 7.2 sec, and soi& is so#t,!apin" 5@ (C


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water tanks lecture 4

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