Wind Dynamic Analysis of Structures

8/9/2019 Wind Dynamic Analysis of Structures

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Wind Dynamic Analysis ofStructures

Engineering & Construction Ventures


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NATURE OF WND !OTON

DA!A"ES CAUSE DUE TO STRON" WND

D#NA!C ANA$#SS OF STRUCTURES UNDER WND

CODA$ %ROVSONS

%RACTCA$ EA!%$E

ADVANCED TO%CS

SA$ENT %ONTS

WIND DYNAMIC ANALYSIS OF STRUCTURES

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NATURE OF WND !OTON


3


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Cyclones

It belongs to tropicl c!clones" #$ic$ %eri&e ll t$eir energ! 'ro( t$e ltent $et relese% b! t$e

con%enstion o' #ter &po)r*E+tr tropicl c!clones re pro%)ce% b! (o)ntin brriers or b!

interction o' ir (sses long 'ronts, 3- . /0 1($*

'urricane

T$e strongest #in% is clle% $)rricne 45)nr1en67, 80- . 3-- 1($,

Ty()oon

5)rricnes re 1no#n s t!p$oons Fr Est7 c!clones A)strli" In%inOcen7

Tornadoes

Most po#er')l #in%s c)sing t$e gretest %(ge, &orte+ o' ir93-- ( in %i(eter7 %e&elops

#it$in se&ere t$)n%erstor(s, (o&e 2-920 1( pre%o(inntl! to#r%s NE, ')nnel.s$pe% clo)%s,

(ini()( press)re t t$e centre o' t$e &orte+* T$)n%erstor(s: c)se% b! $e&! precipittion li1e

#ll ;ets7

NATURE OF WND


/


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!EASURE!ENT OF WND


0


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!EASURE!ENT OF WND * ANE!O"RA!



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0. Unsteady 1a2e flo1 3Vorte4 S)edding5

6. Negati7e Aero Dynamic Dam(ing or

"allo(ing

D#NA!C EFFECTS OF WND

WIND DYNAMIC ANALYSIS OF STRUCTURES2?

Galloping is a form of aerodynamic instability caused by negative

aerodynamic damping in the cross wind direction

)U

z)(d

dCb(CU

2

! "#

2

az

+

z)d

dCb(CU

2

"#a +=

!or $ !zis positive % acts in same direction as&)d

dC(C "#


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0. Unsteady 1a2e flo1 3Vorte4 S)edding5

6. Negati7e Aero Dynamic Dam(ing or

"allo(ing


WIND DYNAMIC ANALYSIS OF STRUCTURES3-

Cross sections prone to galloping '

uare section (zero angle of attac*)

#%shaped cross section

iced%up transmission line or guy cable


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8. Flutter


WIND DYNAMIC ANALYSIS OF STRUCTURES38

Aero%!n(ic instbilities in&ol&ing rottion re 1no#n s @'l)tter" )sing

eron)ticl prlnce" n% re potentil proble( #it$ t$e s)spen%e%

%ec1s o' long.spn bri%ges*


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9. O7aling



+he +ip of Chimney can e,perience radial motion with a number of

lobes around its circumference-

+his is termed as ovalling and the most common motion appears to be

two%lobed oscillation with two cycles around the periphery appearing

li*e a near ellipse at ma,imum amplitude-

Generally occurs$ when the period of circular ring coincides with the

half the period of vorte, shedding-


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:. $oc2*in

Motion.in%)ce% 'orces cn occ)r %)ring &ibrtion pro%)ce% b! &orte+s$e%%ing

Lock-in has been observed many times %)ring t$e &ibrtion o' lig$tl!

%(pe% c!lin%ricl str)ct)res s)c$ s steel c$i(ne!s" n% occsionll!

%)ring t$e &orte+.in%)ce% &ibrtion o' long.spn bri%ges*

T$e 'reB)enc! o' t$e s$e%%ing o' &ortices cn @loc1.in to t$e 'reB)enc! o'

(otion o' t$e bo%!*

T$e strengt$ o' t$e &ortices s$e%" n% t$e 'l)ct)ting 'orces res)lting relso en$nce%*


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Cross.#in% response o' slen%er to#ers

Sin)soi%l e+cittion (o%el :

EB)tion o' (otion ;t$ (o%e7:

;7 is (o%e s$pe

)(tQaKaCaG jjjj =++

;is t$e @generlie% or e''ecti&e (ss h

&

2

. dz(z)m(z)

;t7 is t$e @generlie% or e''ecti&e 'orce h

& . dz(z)t)f(z$

D#NA!C ANA$#SS OF STRUCTURES UNDER WND

WIND DYNAMIC ANALYSIS OF STRUCTURES3/


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Representing t$e pplie% 'orce ;t7 s sin)soi%l ')nction o' ti(e" n

e+pression 'or t$e pe1 %e'lection t t$e top o' t$e str)ct)re cn be

%eri&e% :

==

h

&

2

.

2

h

& .

2

..

2

h

& .

2

ama,

dz(z)tc/0

dz(z)C

t1G0

dz(z)bC

b

(h)y

#$ere ;is t$e criticl %(ping rtio 'or t$e ;t$ (o%e" eB)l to jjj

KG

C

2

)(zU

bn

)(zU

bnt

e

.

e

s ==

2

a

.

b

m1/c

=

Scr)ton N)(ber or (ss.%(ping pr(eter7( &erge (ss)nit$eig$t

Stro)$l N)(ber 'or &orte+ s$e%%ing e e''ecti&e $eig$t 2$37




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T$is cn be si(pli'ie% to :

For )ni'or( or ner.)ni'or( cntile&ers" cn be t1en s 8*0,t$en 1 8*


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Rn%o( e+cittion (o%el Gic1er!Hs)7

Ass)(es e+cittion %)e to &orte+ s$e%%ing is rn%o( process

A non %i(ensionl pr(eter constnt 'or prtic)lr str)ct)re

'orcing ter(s7

In its si(plest 'or(" pe1 response cn be #ritten s :

e1 response is in&ersel! proportionl to t$e square root of the

%(ping

22

2

)3()/45(

6

/

L

aoy

yKSc

Aby

=

@loc1.in be$&io)r is repro%)ce% b! negti&e ero%!n(ic %(ping

!L li(iting (plit)%e o' &ibrtion

Jo non %i(ensionl pr(eter ssocite% #it$ ero%!n(ic%(ping


WIND DYNAMIC ANALYSIS OF STRUCTURES3=


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Rn%o( e+cittion (o%el Gic1er!Hs)7

T$ree responseregi(es :

Loc1 in region . response%ri&en b! ero%!n(ic

%(ping

@Loc1.in

Regi(e

@Trnsition

Regi(e

@Force%

&ibrtion

Regi(e2 0 8- 2-

-*8-

-*-8

-*--8

Scr)ton

N)(ber

M+i()( tip

%e'lection

%i(eter


WIND DYNAMIC ANALYSIS OF STRUCTURES3?


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T$e Scr)ton N)(ber or (ss.%(ping pr(eter7 ppers in pe1

response clc)lte% b! bot$ t$e sin)soi%l n% rn%o( e+cittion(o%els

So(eti(es (ss.%(ping pr(eter is )se% Sc /

2

ab

m1/c

=

2

ab

m1

Sc or J7 re o'ten )se% to in%icte t$e propensit! to

&orte+.in%)ce% &ibrtion

Clerl! t$e lo#er t$e Sc" t$e $ig$er t$e &l)e o' !(+ b eit$er

(o%el7

WIND DYNAMIC ANALYSIS OF STRUCTURES/-

TOWERS; C'!NE#S AND !ASTS * SCRUTON NU!,ER


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Sc or J7 is o'ten )se% to in%icte t$e propensit! to &orte+.in%)ce%

&ibrtion

e*g* 'or circ)lr c!lin%er" Sc K 8- or JK -*>7" )s)ll! in%ictes lo#(plit)%es o' &ibrtion in%)ce% b! &orte+ s$e%%ing 'or circ)lr

c!lin%ers

A(ericn Ntionl Stn%r% on Steel Stc1s ASME STS.8.8??27

pro&i%es criteri 'or c$ec1ing 'or &orte+.in%)ce% &ibrtions" bse% on

J

A (et$o% bse% on t$e rn%o( e+cittion (o%el is lso pro&i%e% in

ASME STS.8.8??2 Appen%i+ 0*C7 'or clc)ltion o' %isplce(ents'or %esign p)rposes*

Mitigtion (et$o%s re lso %isc)sse% : $elicl str1es" s$ro)%s"

%%itionl %(ping (ss %(pers" 'bric p%s" $nging c$ins7

WIND DYNAMIC ANALYSIS OF STRUCTURES/8

SCRUTON NU!,ER AND STEE$ STAC


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For (itigtion o' &orte+.s$e%%ing in%)ce% &ibrtion :

Eli(intes cross.#in% &ibrtion" b)t increses

%rg coe''icient n% long.#in% &ibrtion

$3

$-*8b

b


TOWERS; C'!NE#S AND !ASTS * 'E$CA$ STRA


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Slen%er str)ct)res $eig$t#i%t$ is $ig$7

Mo%e s$pe in 'irst (o%e . non liner

5ig$er resonnt (o%es (! be signi'icnt

Cross.#in% response signi'icnt 'or circ)lr cross.sections

criticl &elocit! 'or &orte+ s$e%%ing 0n8b 'or circ)lr sections

8- n8b 'or sB)re sections

. (ore 'reB)entl! occ)rring #in% spee%s t$n 'or sB)re sections


TOWERS" C5IMNEYS AND MASTS

GUST EFFECTIVE FACTOR METHOD ALONG WIND EFFECT


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GUST EFFECTIVE FACTOR METHOD ALONG WIND EFFECT

Hc1ro)n% Fctor

As per IS 875 - 1993

)st Fctor

)st Energ! Fctor

Sie Re%)ction

Fctor

D(ping

Ro)g$ness

Fctor

WIND DYNAMIC ANALYSIS OF STRUCTURES//

ACROSS WIND EFFECT VORTE! SHEDDING"


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ACROSS WIND EFFECT VORTE! SHEDDING"


ALON WIND RESONSE UST RESONSE FACTOR


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T$e g)st response 'ctors 'or bse b*(* n% tip %e'lection

%i''er . bec)se o' non.liner (o%e s$pe

S$er 'orce : (+ * B

Hen%ing (o(ent : M(+ M* (

De'lection : +(+ +* +

T$e g)st response 'ctors 'or b*(* n% s$er %epen% on t$e

$eig$t o' t$e lo% e''ect" 8i*e* B87 n% (87 increse #it$ 8

WIND DYNAMIC ANALYSIS OF STRUCTURES/ 22-; @

Win% in P Direction

Li(iting : $3-- =


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Win% in P Direction

=8

DEF$ECTON UNDER D#NA!C WND $OAD

r-7o-

#irection U,(mm)

Uy(mm)

Uz

(mm)

() 8ind %9: @-< -&? ?

(2) 8ind % %: @/ 2 2=

( 2/ 2< 2& 2/-2 2 2&-2

CASE STUD# K STATC CASE


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r-7o-

#irection Aasehear(*7)

() 8ind %9: 2;/&

(2) 8ind % %: 2@

CASE STUD# K !ACAU TOWER


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Concrete to#er 2/> (etres >8/

'eet7 $ig$ Tpere% c!lin%ricl

section )p to 2-- (


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CASE STUD# B !ACAU TOWER


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MACAU TOWER0.5% damping

.0--

-

0--8---

80--

2---

- 2- /- - 8--

Full scale mean 1ind s(eed at /8Hm 3m>s5

R*(*s* MenM+i()( Mini()(

Win% t)nnel test res)lts . long.#in% b*(* MN*(7 t >0*0 ( 2>- 't*7

WIND DYNAMIC ANALYSIS OF STRUCTURES>8



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MACAU TOWER

0.5% damping

.2---

.80--

.8---

.0--

-

0--

8---

80--

2---

- 2- /- - 8--

Full scale mean 1ind s(eed at /8Hm 3m>s5

R*(*s* Men

M+i()( Mini()(

Win% t)nnel test res)lts . cross.#in% b*(*MN*(7 t >0*0 ( 2>-

't*7


CASE STUD# * A$ON" WND RES%ONSE


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At eac) le7el on t)e structure define eui7alent 1ind loads

for B

(en #in% press)re

bc1gro)n% B)si.sttic7 'l)ct)ting #in% press)re

resonnt inertil7 lo%s

T)ese com(onents all )a7e different distriutions

Com(uter model calirated against 1ind*tunnel results

Comine t)ree com(onents of load distriutions for

ending moments at 7arious le7els on to1er




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!acau To1er Effecti7e static loads

3sGH m5

U meanG 8@ :m>sM 8J dam(ing

-

0-

8--

80-2--

20-

3--

30-

- 8-- 2--

$oad 32N>m5

'eig)t3m5

Men

Hc1gro)n%

Resonnt

Co(bine%

WIND DYNAMIC ANALYSIS OF STRUCTURES>/



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MACAU TOWER - Turbulence

Intensit !r"#le

-

0-

8--

80-

2--

20-

3--

30-

-*- -*8 -*2 -*3

Iu

Full*scale

'eig

)t3m5

Win%.t)nnelAS88=-*2Mc) H)il%ing Co%e

T)rb)lence intensit! pro'ile :




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Along*1ind res(onse 1as dominant

Cross*1ind 7orte4 s)edding e4citation not strong ecause

of com(le4 (od geometry near t)e to(

Along* and cross*1ind )a7e similar fluctuating com(onents

aout eual; ut total along*1ind res(onse includes mean

com(onent

WIND DYNAMIC ANALYSIS OF STRUCTURES>

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Wind Dynamic Analysis of Structures