wind load on structure parabolic colector

7/18/2019 Wind Load on Structure Parabolic Colector

http://slidepdf.com/reader/full/wind-load-on-structure-parabolic-colector 1/50

SERI/TR-253-2169UC Category: 62eDE85012151

Wind Loadin on SoarCoectors

S. Bhadurl v of Tx l Po)L M. Murphy ol g Rh )

June 1985

Prepred under Task Nos. 1384.30 nd 5102.31

FTP No. 463

Sla Engy ah Inttt Divisin f Midwest Reseh nstitte6 Col BolvdGold Colodo 8040

Ppd o h

S patnt f EngyCo o DC0283CH003



T216

PREAE

Te esea and development desibed in tis doument was onduted witinte U . Depatment o Enegys ola Temal Tenology Pogam Te goal o

te ol Temal Tenology Pogam is to advane te engineeing ands ientii undestandng o sola temal tenology and to establis tetenology base om pivate industy an develop sola temal powepodut ion opt ions o intodut ion into te ompet itive enegy maket

ola tema tenology onentates te sola lux by means o takingmios o lenses onto a eeive wee te sola enegy ·is absobed as eatand onveted into eletiity o inopoated into poduts as poesseat e wo pimay soa temal t enologi es ental eeives anddi st ibuted eeives employ vaious po int and lineous optis toonentate sunligt . uent ental eeive systems use ield s oeliostats twoaxis taking ios ) to ous te sun s adi ant enegy ontoa singe towemounted eeiv . Paabol dises up to 1 metes in diametetak te sun in to axes and use mios o Fesnel lenses to ous adianteeg onto a eeive . Tougs and bowls ae l ineous taking ele tostat onentate sunligt onto eeive tubes along tei oal lines onentated olleto modules an be used alone o in a multimodule systemTe onentated adiant enegy absobed by te sola temal eeive istanspoted to t e onves ion poess b y a i ulating woking luid eeive tempeatues ange om 1° in lowtempeatue tougs to ove1° in dis and ental eeive systems

Te ola Tema Tenology Pogam is dieting eots to advane adimpove ea system onept toug te esea and development o solatemal mateia ls omponents and subsys tems and te test ing and peomane

evaluat ion o subsys tems and syst ems Tese eo ts ae aied out tougte enial dietion o E and its netwok o national laboatoies tatwok wit pivate indust y . Togete tey ave establsed a ompeensive , goaldieted pogam to impove peomane and povide tenially povenop ti ons o eventua inopoation into te nation s eney supp ly

To be suessul in ontibuting to an adequate nationa enegy supply ateasonable os t sola temal enegy must eventually be eonomiallyompet itive wi t a vaie ty o ote enegy soues . omponents and systemlevel peomane tagets ave been developed as quant itat ive pogam goals Te peomane tagets ae used in planning esea and developmentativi t ies measuing pogess asses s ing alteative tenology opt ions , and

making opt imal omponent deveopments Tese tagets will be pusuedvigoousy to insue a suessul pogam

Tis speii epot addesses wind loading sola olletos sine tedetemination o wind loading is one o te majo design onsideations indes igning taking and i eldmounted sola olletos . Te main objet ive ote epot is to eview and assess te pesent design metodology o windoading on olletos o sola temal appliations and to eommend aeas oute investigation o developing ealisti iteia to detemine eliableand adequate ind loads Te eas ib il ity o using innovative des ign onsideations to edue te magitude o ind oads on te sola olletos is also

iii



T-216

consideed . i s epot contains valuae inoat ion egading te compaative studies o vaious aspects o design metodology and sould be ointeest to des ign enginees and developes o sola coll ectos

Te autos wol e to tan te numeous individuals at EI wo povidedvaual di scus si ons and suppot duing te couse o ti s study . Inadito, te autos woud e to tan tose tecnologists outsde o Ewo povded valuabe omments and suggestons in tei eviews o ealiedat s o t is ocumen tese ae Bill elemete , layton avis , Jon Peea ,Jim Leona , a tin ceve, F an Wilins , Kenel Tuyan, Je nleton ,and Aaon oy .

Te i st auto extends is tans and appeci at io to te U . Depatment oEnegy DO and te Ameica ciety o Engineeing Education AEE o teoppotunity to do t is eseac at E I Ti s aea o eseac is suppotedby te DOE ola Temal Pogam unde te diection o Fan Wilins andati ceve .

BaduiUnivesity o Texas at El Paso

Appoved o

LA ENEGY EEA INTITUTE

Temal sems ad Enieei Ban

aon iectoHea esea Division

iv



S Y

Objecive

Te bjetive is to eview and assess te peset metodology o peditingand des igning o wind loading on soa oll etos o toug di s andelosta apliations and possibly o lage iedmounted potovoltaiaays Anote obj et ive is to eommend aeas ute invest igation odeveoping ealisti iteia to adequately deemine te wind loads on tesestutues

Discussion

Te pesent metod o det emining te wind load us ing te odeANI A8 1 182 o te Ameian National tandad Inst it ute is ovely onsevative Te eent model studi es o sola olletos in bounday layewind tunnels unde simulated atmospei low onditions yielded valuableinomation egading te wind oes on te olletos and establised vaious dimensionless oe and moment oeiients oesponding to te meanwind veloi t ies and tei diet ion o appoa A si gnii ant amount omodel testing was devoted to studies involving bot individual olletos andi elds o ollet os Te ee ts o poous enes o baies at te edge ote olleto ield and te sielding eets o te adjaent olletos inte ield in eduing te eetive wind loads on te olletos wee alsos tudied in te wind tunnels at vaious test ail it es Te esul ts o tesestuies indiate tat te wind load an be edued onsideably even beyondte levels tat toug designes ave aleady used

nclusions Reconaions

In ti s study te ollowing wee aompl ised

Development o elevationdependent longitudinal veloity poiles ovaious exposue onditions

ompaative study o te total oe oeiient o a lat plate ovaious aspet atios and at vaious angles o at tak Values obtainedo te ANI A8 1 18 2 ode AE Task omm 16 1 [ 2 ] and ullsaleeliostat tests wee used o te ompaison

ompaat ive study o te spet a o longi tudinal vet ial and late alveloity lu tuat ions pet a o te veloity lutuat ions o equeny ange 1 1 wee alulated and omaed gaially Tespeta used o te Buil ding ode ANI A8 1 182 and te s pet a inKaimal et al [ 26 ] wee onsideed

Estimation o te esultan angle o attak ( elative to te oiontal)o te tubulent wind ield o vaious exposues su as open ield andsububan loati on Tis is pat iulaly impotant wen onside ingelios tat s in te stowed pos it ion Te angle o attak due to tubulentlutuating veloity is stongly dependent on te ougness paamete ote low ield Fo a ougness element o 12 m ( 4 t) in a

v



-216

sa aea ad wid spes p mp an m at an eeatio o m 2 . 8 e agls o atak de to lang etiaeloit ae .68 ° and 3 ° espetely.

emmendatns o te sies at migt ede te wi loadig o eoeto ae to

• diy te low oa sg a tlne stimato i e om ooos eas aond e eliosta o disoage te ow sepaaon ate s e eosat

• teine exienta e apopiae ai gap beween te mles oag etiio aod te od

• td e eets o pemete es an enes e ad agp esat os to e e eal wd ld

• etemn te magde o win speed an is dietion deeloping awin ose o te sta ied . sa sae mo o seisat ed may e tsed i t atmospe id tnel oaninmat ion egadig e wd speed its deti on d teaati stis .



T-216

TLE O S

1 . Intodution . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1

2 . Estmates o Wind oes . . . . 5

2 . 12 . 2

Atmospei Tubulene peta

aiat ion o Wind Angle m te Hoional .

. edution o W Loading . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

12

2

. onlusion and eommendations . . . . . . . . . . . . . . . . . . . . . . 2

5 e enes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

vii



269

LIS OF FIGS

1 Distibution o Gadient Wind o Vaious Eposues 9

22 Vaiation o Wind peed wit Elevation u0) = 27 mp 4

2 Vaiation o Wind peed wit Elevation u0> = 50 mp 14

2�4 Vaiation o Wind peed wit Elevation u0) = 7 mp 15

25 aiation o Wind peed wit Elevation 0) = 90 mp 15

26 Vaiation o Veloit Pessue wit Wind Veloity 16

27 A Geomety o Flow past a Flat Plate 17

28 Vaiation o Foe oeiient wit Angle o AttakA spet at io = 1 0 18

29 Vaiation o Foe oeiient wit Angle o AttakAspet atio A = 0 19

20 Longit udinal ubulene peta U = 447 mp 22

211 ubulent Wind peta U = 447 mp 22

212 ubulent Wind peta U = 900 mp 2

21 tong Wind Veloity peta o Daniels 24

214 Peak Angle o Attak due to ubulent Lateal Veloity 27

215 Peak Angle o Attak due to ubulent Vetial Veloity 28

viii



T216

LIST OF TLES

2-1 Gadient Wind

82-2 aiation of Wind Veloi ty wit eigt

2 . mp 1

2- Vaiat ion o Wind Veloi ty wi t ei gt . mp 1 1

2- Vaiation of Wind Veloi ty wit eigt . m 12

2- aiation of Wind Veloity wit eigt . mp 1

2-6 Veloity Pessue. . . . . . . . . . . . . . . 16

2- Foe oe i ient

o Flow past a Flat Pate Aspet at io

1 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1

2-8 oe oeiient o Flow past a Flat Plate Aspet at io

. . . . . . . . . . . . . . . . . . . . . . 18

2- Dimens iones s onstants o Longi tudinal and Lat eal Tubulenepe ta . . . . . . . . . . . . . . . . . . . . . . . . . . . 2

2- 1 Vaia ti on o Angle o Att ak due to Flutuat ing Lat eal Velo ity 26

2-1 1 Vaiat ion o Angle o Attak due to Flutuating VetialVelo i ty . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2

ix



A , B , C , D

n

q

qS , n )

Sw ,n)

Sv ,n)

U)

g

*

v

w

T

basic exposure categories

characteri st ic surface area of collector , m ft )

force coefficient, dimensionless

moment coeff ic ient , dimensionless

wnd force , N bf )

drag orce , N bf )

lift force, N bf)

Monin coordinate , dimens ionlessgust response factor at height = h, dimensionless

velocity pressure exposure coefficient at height

moment arm length, m ft)

moment of a force , N m bf ft )

frequency, H

dynamic pres su re , N/m b/ft )

velocity pressure evaluated at height , N/m b/ft )

26

spectrum of longitudinal veloci ty fluctuations , N m/n bf ft s )

spec trum of verti cal veloci ty fluct uati ons , N m/n bf f s)

spectrum of lateral veloc ity fluctuations , N m/n bf f t s )

mean velocity at height

longitudinal component of velocity at gradient height glongitudinal component of velocity at height

friction velocity, m/s ft/s)

basic wind velocity, m/s mph)

vertical elevation, m ft)

reference height of ANSI code, m ft)

gradient height , m ft )

reference height , m ft )

angle of attack, degreecoefficient /r)c

aspect ratio

mass density, kg/m slug/ft )

stability parmeter

frequency, H



R-2

ETION .0

INTRODTION

Drig the last two decades there have bee a mber of s igif icat developmets i the mete orolog ical aspect s of the wid-loadig problem Advaces istrctral desigs particlarly for high-rise strctres reqired accratead more reliable meteorological iformatio abot the wid-loadig process es Varios research reslt s ad hist ories of fai lres of st rctres [ ]idicate the damagig effects of repeated wid-idced loads o strctresEfforts have bee made to desig strctres that resist he repeated loadigact io of wid [ 2 ] his cotradi cts the re coveti oal desi g approachwhich is maly cocered with static applicatio of a sigle large loadderived from the gidelies frished by the Natoal Bildig CodesExpeiece sggests tha serviceability de to repeated loadi effects is amore likely occrrece tha serviceability or collapse from a sigle applicat io of a except ioally large load [ 4 ] he coo types of st rctralserviceabil ity cased by repeated wid loadig are fatige failre2 fodatio settlemet excessive deflectio ad 4 idced motio ofaccept able level Fatige failre is a importat desig cosi derati o evefor the des ig of low-ri se st rctres Examples of fat ige failre de towid are fod i strctres sch as towers lam stadards chimey stacksad eve bridges [ 5 ] iovative cocetrator desigs becoe less robstto redce the amot of aterials ad costs reqired all of these issesbecome more of a cocer example of sch a lightweight cocetrator isthe stretched-membrae heliostat

id is oe of the pricipal loads actig o above-grod egieerig strctres accrate determiatio of wid loadig is a fdametal desig co

sideratio i decidg what degree of safety d ecomy ca be achieved isch a s trctre It is como practi ce to desi g s trctres to res i st thehighes t wid to which they may be sbe cted he highest wid is dete rmiefr the aalysi s of extre vale s tat is ti cs of reco rded wid veloc ities fora log period of time for a particlar regio

he wid loads are cosidered i terms of a steady appled force idepedetof the strctres shape sie ad dyamic characteristcs ad a coefficietdeotig the amplificatio that ca arise throgh the iteractio of thespermposed pres sre flcat ios ad the strctres dyami c respose hereliable estimate of this coefficiet is qite ivolved ad reqires detailedkoedge of the s ite-speci fi c wid climatol ogy he wi speeds sed i cr

ret desig specificatio are based o the eather Brea observatio ofthe fastest mile of wid from distribtio of extreme wid i the Uitedtates mltiplied by a gst factor to allow fr the flctatios i t widspee he gst respose factor is a measre of the effective dyamic loadprodced by the gsts ad is iteded to traslate the dyamic resposes prodced by the gs t loadig ito simpler sta ti c des ig crite ria Althgh this

Fastest mile correspods to the highest extreme wid speed i miles perhor measred at a stadard height of ft above the grod level i aope-cotry locatio



R

approach has often result ed in a sa fe , conservat ive es t imate of wind oading,the neglect of the dynamic properties and si e of the structure , the sufaoughness, obstructns , and the wn directons and their frequenciesinherent in applying the fastest mile of wind could result in unsafe stuctures or in costly vedes igns

llo and ohen [ ] eveloe a design methodolog based n a power spectrum analysis o the dynamic structural response of a simple linear singledegree of freedom system wth iscous damping and reported measurements ofwind gu st spectra and gu st correlat ion coeffi cients he results of theanalysis are presented in equations and charts that permit us to determine thegust response factors for buildings and conventional strutures However, forstructures like solar collecto rs , the method is not sati sfactory since it doesnot account or the ef fects of suface roughness , t errain charact er ist cs , anddi rect ional di st ribut ion of wind We st il l do not underst and the mechanismwhereby gust pres sure is induced on groundbased st ructures Moreover , thesedesign guidelines are applicable only to the situations where the principalwind loading is drag ateral and vert ical wid components normal to he

gros s flow di rect ion and gus t iness are not conside red

Davenport [ used a st at is ical approac to e st imae the mean gradi ent windspeed that has a specified return perod or probability of exceeding on hebasis of the mode and dispersion factor for the extreme gradient wind speedf ield at the site of the str ucture his method may be used to determine themean wind speed a some speif eght ove e ground if a reliablees timate of ground roughness and exposure of the si te is avai lable heground roughness is the principal parameter governing the mean wind speedpro fi le and gus t iness Knowing the mean wind speed at the st ructure heightcorres ponding to the grad ient s peed and the ground roughnes s , we can de inethe vertical and horiontal gust spe ctra Davenport based his esimate o the

gust force superimposed on the mean wind forces on the lateral gust spectra

In his pioneering paper, Davenport [ ] outlined the rationale for determininthe des ign wind veloc it ies Bri efly , he cons idered the extreme values tati st ics of the si te , speci fic wind veloci ty, local ground roughness andexposure characteri st ic s , wind di rect ion roset tes , and a weightingparamet er he methodology outlines the determination of the basic des ignwind velocity that corresponds to the extreme sustained wind veocity givingri se to the steady component of the press ure his veloci ty s ess ential l aaverage veocity, and the determination of a suitable averaging interval is aimportant feature of the method Davenport attempts to process he recodsfrom a wide variety of anemometers of differing exposures and periods of

records ad to determine statistically how the records may be related to neanothe r his minimies the systematic errors that may arise i the recodsbecause of uncontrolled anemometer siting and improves the records overallrel iabi lit y he influence of the local surface rougness on both the magnitude of surface velocities and the increase of velocity with height is verimportant Combining these resu lts with extreme value s tat is tics [ ] leads toa qualitative method through which basic design wind velocities of a givenprobability of occurrence may be predicted for locations of differing surfaceroughness



R-2

h ded he ep f he l fe le wd peed hee vle ee f wd peed f deg ppe he phl delf e d he le w ed hve d level f 4 ( 30 d el pfle g 7 pwe lw Cp l ehdwee develped f fg he Fhe-ppe pe I exe vle d

0 whh f ed he d well he ehd develped e ppled he p d pe- d ee f 38 p wee df he 2-e 0-e d 00-e e eee evl hee peeved geel ee he dd he e hd f deeghe qe h ple f fxed ped d fdeel f he ee ed f he p wee gve

I h eqe ppe h eved h he d f helgh Fhe-ppe pe II (Fehe d lgh f f he pe I d Alhgh h f w ed he pev ppe fhe ex f he exeve exee wd d hwed h h d fllw lg l dlel whh wld de pe I d f he exee f helgh h l e he vld f e he f he Fehed f exee wd he p develped h whh hepe I d f de 0 wee edexeel e AN dd f ldg de f he Ued e hep dep ed he eh e le pe h f he l exee le 00 ( 33 f ve he gd f 2-e 0-e 2 -e 0-e d00-e e eee evl

he wd peed ed deee he deg wd ld ldg dhe e e gve Fge f he ANI A 8 - 82 de 2 fhe g Ued e d Alk d le 7 f Hw d eR p el de e llwed f he eg f whh ed

expeee de h he wd peed e lghe h he ded Fge d le 7 f he de 2 he ANI A8 - 82 de lllw e f he wd peed ed egl cl d dexee vle l l hweve he wd peed e le 70 ph

Al veg egze he qlve e f e elzed ehle ed d lleed de dvee d d gge h hee ed wh ge e deeg he wd ld f pef e pef e Ofe he pl f exeedg pl wdvel f e eee evl eled he degee f ked wh he lfee f he e he pl h

e wll e j eed gde f wd ldg e pefe wd d d efle he e e f wd d hee qe he gd ghe he expe fee wd de d e d e lded he ehd lg ed hede

he e Nl dd A8 - 8 2 2 def f degwd peed e f he e eee evl e ped F e eee evl he epdg deg wd peed lledf he expe f he lve d f f he exeewd he pee f h f e eed f he d f he

3



R26

argest w nd speed for every year on record. The mean recu rrenc e inte rval to

be used n the design is se lec ted as a func tion of "intended operational

u sge , antic ipated lfe of the structure, degree of sensi tivity to wind and

the isk of loss of hu man life and property in case of failure" [ 1 2 ] .

Im lc it in the selection of the mean recurrence interval is the assu mption

that a given recurrence interval will ensu re the same level of sa fety for any

two stru ctures su bj ected to wind oads prov ed tha the reliability f thetw t rtre eql 3 ] exed the vldt f th plfedt d hwd lvel tht the e f deg wd p ed the tdrd e rerree tervl de t ere tet level ff et r t rtre j eted t wd ld ephzed tht exteve reerh reqred t develp regl d tpef wd peedprv ed rellt dert

Be e f the ertt d qlttve tre f the ethdlg e tett wd ldg trtre t ee rele t t the degpreter fr lt tde f te der vr wd peed d wddret Vr lt ed experetl tde the wd tel hve

lred elded vlle frt

rph 4 ] revewed the ex tg ethdlge fr e ttg the wdldg lr lletr He rzed 33 tde relevt t wdldg lr lletr heltt d phtvl t rr he reprt whh t vlle frt regrdg the preet tte f the r t h ee ed gde fr th td

Rh [ ] exed the prle d plt rg fr wd ldg lr etrtr He ephzed the tepe tre f wdldg wth ted prtt erg the deg t perfre pert d tee fet rvvl d repleet f lr l

letr prtlrl the prldl etrtr

he prr jetve f th td t revew d e te preet degethdlg wd ldg lr lletr prtlrl th helttd t reed re f frther vetgt t defe relt rterfr dete rg deqte wd ld he del te tg f the lr lletr the evretl wd tel 6 7 ] dte tht t plet rede the wd ld derl I vew f the felt f ldredt we pre tde f the ttl fre effet f flt pltef vr pet rt d t vr gle f ttk d tde f thepet r f lgtdl vertl d lterl velt fltt hegle f tt k f the trlet wd t the hrztll pled flt pltere prtt e e f ther effet the et et f the trtre ettept t ette the gtde f gle fr trlet petr l

h td de t der the wdldg effet ed trleee ffetg ( 2 ) vrtex heddg fre pr ded the trtrew wke tg the fterd f the trtre ehd the eprt pt d 3 erelt fre ded the lltg t f the trtre

4



R-

SEION

ESTITES O VN S

he wind load on the low-height st ructures , such as heliostats extending oera large land area , is a maor des ign conside ration roperly determining thewind loads on the heliostats is essential for realistic structural designs andcos t estimates he S A8-8 code [ ] is commonly used as a designguide he code is primari ly deeloped for bui ldings and other st ructuesGenerally , est imates are made , in the absence of more rel iable exper imentalvalues obtained frm model study, by considering the eliostats as otherstructures

he wind force F on a structure is gien by

where

q = elocity pressure ealuated at height aboe ground lb/ft ) *

Gh = gust response factor at height = h

Cf = force coefficient

Ap = proected area normal to wind

he elocity pressure q is calculated from the standard formula [ ]

q = KV

,

where

K = elocity pressure exposure coefficient at height

V = basic wind speed mph)

-)

-)

he alues of the arious coeffcients and factors are taken from the tablesproided in the code for arious expQsures of the site of the structure Anexposure category is determined for the site at which the structure issituated t reflects the character ist ics of ground surface i rregulariti es .

Generally , four basi c expos ure categories are consdered Expo sures A , B Cand D repres ent the large ci ty cente r, urban and suburban areas , open terrain ,and flat , uobstructed coas tal areas , respectively

*Since the standards and codes used for comparative assessments are describein their or iginal form us ing Engli sh units , S units will follow the Englishequivalents



TR-2169

The structure is designed fr the envirnmental cnditins with specified wndspeed and mean recurrence interval Generally perating envirnmental cndiins and extreme envirnmental cnditins with assumed mean recurrenceinterval and expected life f the structure are cnsidered t estimate heprbability f exceeding the maximum design wind velcity. The prbabiliy isderived frm the cnsideratin f the extreme value rdered statistics f Th[9]. The prbability f exceeding the design velciy r risk f ccurrenceas it is called is nt ased n site-specific extreme wind recrds. Therecrded wind data at the airprt f a relatively large city may nt beapplicable t a smaller suburban city 50 miles away with different terrainfeatures. n fact Simiu [13] Davenprt [7] and McDnald [18] have questined the validity f the basic assumptins and simplifie methdlgy.The variati\ f lngitudinal cmpnent f wind velcity with elevatin n theearths lwer atmsphere is expressed by

Uz = Ug (g

( -3)

whereUz = lngitudina cmpnent f velcity at height zUg = lngituinal cmpnent f velcity at gradient height zg

n = an expnent.

The fllwing analytical relatins f the velcity prfiles relative t thevelcity 30 at a height equal t 30 ft have been derived fr ready reference.

ExpsureC

zg=

900.0 ft n=

0.1429 - 0.1429Uz - U3 30psure B zg = 1200.0 ft n = 0.2222

z 0.2222Uz = 3 30Expsure A zg = 1500.0 ft n = 0.3333

z

0.3333Uz=

3 30

(2-4)

(2-5)

(2-6)

The lngituinal cmpnent f wind velcity at elevatin z = 30 ft fr theexpsure cnditins A B and C are related by

and (2-7b)

6



TR2169

Tab 2 shows th dstrbuton of gradnt wnd for varous xposurs. Fgur 1 graphcay shows th dmnsonss gradnt wnd dstrbuton wthvaton for th xposurs of A, B, and C. Tabs 22 through 25 gv thvaus of th vocty varaton wth hght for rfrnc vocts of

27.0 mph, 50.0 mph, 70.0 mph, and 900 mph, rspctvy Fgurs 22 through25 show th varatons of wnd spd wth vaton for th xposurs.(30) s th vocty of wnd at an vaton = 30 ft for xposr catgoryC. Tab 26 gvs th computd vaus of vocty prssur otand from thformua q = 0.00256 2• Fgur 26 shows th varaton of vocty prssur wth wnd voctyn rcnt yars, th mod studs of structurs n smuad fow fds hav ydd mor rab wndoad dsgn vaus xprssd n trms ofdmnsonss forc and momnt coffcnts. Th arodynamcs of structursn turbunt shar fows of th arth s owr atmosphr nvov nonnarntracton of th turbunt approachfow wth hghy compx turbntboundary ayrs and subsqunt boundary ayr sparaton and turbunt wakformaton. Crmak [9] and Bhadur [20] showd th fasbty of smuatngth arth s boundary ayrs n th propry dsgnd wnd tunn.Lndsay [21], Randa t a. [22] Pgow [6] and Xrkos t [7] tstdth mods of ·th soar coctors, hostats, and hostat arrays n thnvronmnta wnd tunns and prsntd usfu xprmnta rsuts thatcoud b usd for dtrmnng dsgn wnd oads.Basd on th prncp of smtud n mod studs, th quaty of thforc and momnt coffcnts for th mod and for th prototyp, rspctvy, s w stabshd. Th forc coffcnt C s dfnd byf

whr

FCf = qA p

'

F = rsutant forc actng on th structurq = dynamc prssur, oftn cad vocty prssurA p = projctd ara norma to wnd.

Th momnt coffcnt CM s dfnd by

whr

MCM =qA

p

L

'

M = momnt of th tota forc abou a rfrnc pontL = a charactrstc momnt arm ngth.

Th dynamc prssur q s xprssd byq = 22

(28)

(29)

(20)



5,1*'

(ft)

1534575

123456789

1

1112131415

Table Gradient Vind

=

9 ft(27.32 m)

/

U/Ug

.17 .557.33 .615.44 .641.56 .662.83 .71.111 .731.222 .87.333 .855.444 .891.555 .919.667 .944.778 .965.889 .9831. 1.

=g

/g

.13.25.33.42.63.83.167.25.333O417.5.583.667.75.833

.9171.

8

B

12 ft(365.76 m)

U/Ug

.378.441.47.494.54.576.672.735.783.823.857.887.914.938.96

.9811.

2169

A

g

=

15 ft(457.2 m/g U/Ug

f.1 .215.2 .271.27 .299.33 .322.5 .368.67 .46.133 .511.2 .585.267 .644.333 .693.4 .737.467 .776.533 .811.6 .843.667 .874

.733 .92.8 .928.867 .953.933 .9771. 1.



1;0

xpo go: g B d C op

04

02

02 04 06

UUg08

vg

0

Figure Distribution of Gradient Vind or arious posures

whrp = mass dnsity airU =

man apprah vlity.

Th wind ts an b rslvd int tw r mpnntsdrag r andlit r . Thy ar prssd as D

whrD = drag iintA p = prjtd ara nrmal t th wind;

and

whr = lit iint.

rm th vtr natr th r and its mpnnts it an b shwn that = F

D



s- • !

Elvatin(ft)

0IOI20

240so7

IOOIO200300soo700900

1000OOI2001300I400OO cnvrtbT cnvrtc cnvrt

TR-2I69

able - araton o Vn elocty wth Heght,30 = 27 mph (I2 m/s)

ExpsurC

ExpsurB

ExpsurA

Wind Spd Vlcity Wind Spd Vlcity Wind Spd Vlc Prssur v Prs sur� v Prs su(mph) q (lb/ft2)c (mph) q (lb/ft ) (mph) q (lb/f

0 0 0 0 023.I 1.37 I.2 O.9 8.3 O.I824.6 . I6.6 0.71 9. 0.22.6 1.68 I7.7 0.80 I0.4 0.28

26.4 1.78 I8.6 0.89 II.2 0.3227.0 1.87 I9.4 0.96 I2.0 0.3728.20 2.04 20.7 I.IO I3.2 0.429.2 2.I8 21.7 1.2I I4.2 O.2

30.86 2.44 23.8 1.46 I6.2 0.672.2 2.6 25. 1.64 I7.9 0.8234. 2.98 27.7 1.96 20.4 1.073.4 .2I 29.6 2.24 22. 1.037.6 3.62 32.3 2.67 2.7 1.6940.2 4.I4 36.2 3.3 0.O 2.3842.4 4.60 9.0 3.89 34 .I 2.9844.0 4.96 4I.28 4.36 7.I 3.2

42.3 4.8 38. 3.7943.2 4.78 39.7 4.044.0 4.96 40.9 4.28

42.0 4.243.0 4.7344.0 4.96t m multiply by 0.3048.t m/s multiply by 0.447.t Pa multiply by 47.88.

IO



TR2169

Table 3 a W lcy wh Heh30 = 50 mph (22 m/s)

Eevatin(t)a

Expsue C Expsue B

010152025

3040 50

75100200500700

90012001500

ind Speedv(mph)b0

428454473488

50052539571595657749786

815

VecityPessuep (b/t2)c04.69

528573610

64068744

8.35

906110514361582

1700

ind Speedv(mph)0

281308328345

359383040244.0

46954767723

76.5

815aT cnvet t m mutipy by 03048bT cnvet t m/s mutipy by 0447cT cnvet t Pa mutipy by 4788

and =

( 2 + 2

)

1

D L

Vecityessuq (b/t )

0202 243275305

330376414496563766

11531338

149017 .oo

Expsue Aind Speedv(mph)

0153176193208

2212440262300331416565632

687757815

VecityPessueq (b/t2

0060079095111

125152176230280443817

1023

12081467100

(214)T cmpae the vaues C btained by using the guideines theANS A5811982 cde with the vaues btained by using the methdgy theASCE Task mmittee 1961 [ 23] ws past vetica pates with aspectatis A = (width/height) 3 and 1 ae cnsideed (see Figue 27) Theexpeimenta esuts Pegws [16] u-scae test a eistat aspectati A = 10 ae as used the cmpaisn F anges attack 0°30° the cespnding vaues ce ceicient C ae taken mTabe 11 ANS A5811982 cde [12] and Figue 5(d) Pape 3269 the

11



5f l'* TR'

Tbl 2. o o locy w 30 = 70 p (3

levtin pe

(ft a ind Speed elcitv Pe(pb p (lb/ft c0 0 0

0 98 9 634 090 66 930 700 4so

73 400 83 76800 98 7300 973 44400 04 6300 046 80600 074 93700 098 3086

800 9 306900 38 330000030040000

T cnvet t ltipl b 03048T cnvet t / ltipl b 0447cT cnvet t Pa ltipl b 4788

pe B

ind Speed elcitv Pe2(p q (lb/ft 0 0

393 39

430 4.73

48 37

0 643

6 8096 098764 494836 78989 037937 48976 439

009 606

040 769068 90093 3086 38838 33

pe A

ind Speed elcitv Pe(p q (lb/ft 0 0

4 74 670 873090 44

3663.43

46 468 8676660 36733 37790 98839 80883 996

93 896 39994 906 6907 86008 304 36638 33



5�1! TR-2169

Table 5 ariation of Vind eloity ith igt,30 = 90 mph (0 m/s

Elevatin Expsure

(ft)a

Wind Speed Velityv ressure(mphb q (lb/ft20 0 0

10 77 o 15.1815 81.6 1.0520 85.0 18.0525 87.7 19.69

30 90.0 20.7 0 93.8 22.5250 96.1 23.675 102.6 26.95

100 106.9 29.25200 118.0 35.65500 13.5 6.31700 11.2 51.0

900 16.35.79

12001500

T nvert t m multiply by 0.308.bT nvert t m/s multiply by 0.7.T nvert t a multiply by 7.88.

Expsure B

Wind Speed Velityv res sur(mph q (lb/ft 0 0

50.5 6.5355.3 7.8358.9 8.8861.9 9.81

6.5 10.6568.7 12.0872.2 13.379.0 15.988.2 18.1598.3 2.7

120.5 37.17129.8 3.25

137.3 8.2616.3 5 4.79

Expsure AWind Speed Velityv res su(mph q (lb/ft

0 0" 27.5 1.9

31.5 2.53.7 3.0837. 3.5839.7

.03 43.7 .89 7.1 5.6853.9 7.59.3 9.007.8 1.32

101.5 26.3713.5 32.98

123. 38.98135.8 7.2116.3 5.}9

Task Cmmittee (TC [23]. The results are shwn in Tbles 2-7 and 2-8. Theyre als presented graphially in Figures 2-8 and 2-9.The rtis f Cf (de/Cf (TC and Cf (de/Cf (helistat indite that thede values within the range the angles f attk re generally 10% t25% higher fr A = 1.0. Fr A = 3.0 they are 22% t 25% higher. Thus thede gives an verestimte f the wind lads fr the flw past an inlinedflat plte. The values f Cf estimated by using the Task Cmmittee guidelinesmpare favrably with the experimental results f the full-sale helisttetin. Fies 2-8 and 2-9 shw that the ANS effiient Cf is mdertelynse l ss 1 and tht it i mewhtmre nservative higher ngles f ttak. Fr lnger lates the devalues are generally mre nservative.

13



5= ·1 " �-

�=.

c0:>Q

[

1 0 20

Wind speed (mph)

TR-269

Exposure categori es:A. large ci ty center

B. urban and suburban areaC open terrain

30 40

Fig 22. ariation of Vind Speed with Eevation, (u 0>c = 27 mph

-

�

c0·.>Q

[

20

�

0 20 40 60 80Wind speed ( mph )

Figre 2-3. ariation of Vind Speed with Eevation, (u 0>c = 50 mph

14



s-�•

c>

200806040200080604020

0

R

xpos goi s lg i B d s C. op i

0 20 40 60 80 00Wid spd mph)

Fire 4 ariaion o Win Spee wih evaion (u 0c = 70 mph

c>

xpos goi s. lg i

B d s C op i

Wid spd mph )

ire 5 ariai o Win Spee wih evain 3c h

5



d VelctyV (mph}

1020304050

60708090

10012014060180200

\

Table 6 elocity Pressure

Dyamc ressure Wd Velcty amc ressureq = o00256 v2 (lb/ft2}b v (mph} q = 000256 v2 lb/t2}

0261025416492

126164272563705026558301024

220240260280300

J

124147173201230

T cvert t m/s multply by 0447bT cvert t a multply by 4788

�

"Q

d vlo )-

Vlo p 00026V

wh V wd vlo ph

d vlo ph)

Figu 6 ariation of elocity Pressure ith ind eocity

16



Tb aba

1

I·

a

re 27 A ometry for Flow past a Flat Plate

Table 27 Cf for past a at Plate a

t at

nl tta

d ltat

ad

d

2

2

valu a

l [ ]

d

4 9

vn nly u

Ta mm

FullalT Tt

9 9 2 4 4 4

9 2 9 4 2

t °

T29

d

hlitat

5 9

2



S= l.

. " �I�

Table 8 C o ow past a Flat PlateAspct Ratio, 3 0

Angl of Attac f ffcode

(deg ) Cod Tas Comm f

0 0 0 010 o 70 0 5 7 1 31 5 0 9 0 07 1 5 0 0 9 5 o 78 1 5 1 0 5 0 8 4 1 530 1 1 0 0 8 8 1 5

69

An important fatur of th ANSI cod is that the minimum angle of attac is10 The cod os not consider any angl of attac lss than 10

The selction of th angle of attac, particularly in the stowed horizontalpos it ion of the hlio stat , must b mad with careful cons idrati on of themtorological and turbulnce charactristics of th high sped air flowNormally the air flows horizontally or the surfac of the earth with a rlat iely small rt ical component Te ertical componnt arises from two basicsourcs : surface roughnss and instabi li t ies in the air causd by tmperature , dnsi ty , and moist ure di ff rncs Th fi rst sourc is s sent iallymechanical and th scond is thrmodynamic In the presnt study , our primaryconce is mainly for the situation whn surial requirmnts 90-mph winds dic tate that th hlio stats b placed in the horizontal stow posi ti on Such

;QQ

0

spect rati, 1 0

I 581 {1982)

C task cmm ittee {1 961 )

5 35

ngle attack, {eg)

Fiue 8 aiation o Foce eicient with le o AttackAspct Ratio, 1 0

18

N00



cQ(

Q0(Q(0

0

T29

pt rtio .0I 58. 82)

35

ngl o tt g)

ire 2-9 ariation o orce eicient with le o ttackst at, =

nd nrally urs durn nutral atmsr stablty, and tr sl tt l vrt al mvmnt f ar ausd by trmdynam ffts t aarstat t dmnant auss f t vrtal mnnt f ar vlty ar turbuln ff ts T fr f turbulnndud vrt al flutuat n ar

atn n t rzntal lstat an b stmatd frm t knld f tturbulnt nry stra f t ara nd

1 SPHIC SPE

T randm flutuatns f vlty n a turbulnt fl asn a nt n tfl fl d may b ausd by t sur st n f t lal vrt s r dds ,a t a randm mtn f rquny n (al tat vly f av numbr k) Wan arxmat t ttal knt nry f t turbulnt mtn by summnt ntr butns f a ddy n t fl Wn t quat ns f mt n fturbulnt f l ar arrat ly transfrmd and analyzd , t an b sntat t nrtal transfr f nry frm t larr dds t t smallrdds taks la; t vsus dssatn taks la rmarly n t small st dds tru sar dfrmatns T asad rss f knt nrytransfr frm t larr dds t t smallr ns , and ult matly nryd ss at n nt at , s t bas stu lat f Klmrvs yts s

asurmnts f turbulnt stra n t surfa layr f t atmsr substantat t valdty f t assumtns rardn t turbulnt nrytransfr mansm n an dal zd rz ntally mnus , nutrallystabl fl, t nry rdutn rat s arxmatly baland by tnry dssatn rat

9



TR-169

Th ind locy ari s randomy h im As a rsul , n prss urson h surfac of h srucur a no sady hy also ary ih im Thman squar dnamic pr ssur is rlad o h man squar lon iudinallociy flucuaions hich implis ha h prssur spcru is propori onal o h scrum of h longi udia loc iy h sp crum of dynamicprssur can b prdicd from h non longiudinal lociy spcrum

Th simaion of gus rspons facor usd o drmn h nd forc onh scu is basd on h dsign mhodology dlopd by Vllozzi and [ 6 ] Th mhodology us s h rsuls of h por spc rum analys is ofh dynamic srucural rspos of simpl linar singl on dg of frdomsysm ih iscous damping and masurd ind gus spcra and gus corrlai on cof fi cin Th ari ous urbuln ind spcra , comonly usd in hsudy of lor mosphr , a r compard o ass ss h nrgy spcra usd inh ANSI bui ld ing cod

Th spcrum S ( z ,n of h longiudinal lo ciy flucuaions in h inrialsubrang can b prssd in h folloing normalizd fom [4 ]

hr

f =

u * =

z =

U( z =

n S ( z

z

n ) = 0 . 6 f-3 ' (-15 u *

n Z= frquncy

U( z ' n

fricion lociy

laion

man lociy a high z

Th lf -hand mmbr o f Eq 1 5 is call d h rducd spcrum of hlongi udinal loc iy fluc uaions and is a funcion of high S imiu [ 5]considrs Eq - 1 5 a good rprsnai on o f spcra in h high-frquncyrang and suggss using i for f > 0

Th longiud inal nrgy spcra currnly mployd in h ANSI A58 1- 198building cod can b prs sd by h fol loin mprical rla ion [ 5 ]

hr

X = 100n

(

10

n S ( z,n 4= (-16

( 1 + 4/3'

'

IU( 10 = man ind spd a high 1 0 m (mph, m/s

Equai on - 16 as oba ind by araging h rsu ls of h asurmns aario s h i o s o , hrfor , sho h dpndnc of spc ra onhigh

0



T-2169

n the low-freqenc range the energ spectra cannot be described b auniversal relation Kaimal et al [2 considered te limiting value of thespectra as f approaches zero, and th product n S(z,n) reaches a maximum valeat f = fm suc that < f < f Equato 2-5 is valid beond the value off

=

f Kaimal et al [2�

proposed the following empirical relation for theongitdinal specra in the lo fqen ange: n S z,n) 2f-u2 = T5oi)13"

(2-17)

Equation 2-17 approximates closel the spect in the higher frequenc rangealso, and Simiu [25 sgsted sing it for the entire sectruThe spectr that Luml and Ponofs [27 developed for the vertical andlateral velocit flctuations in the lower surface laer of the atmosphere areien, respectivel, b the emirical relations

and n S w (z,n) 336fu2*=

(_lO) S/3

n Sv(n) !S-

:

= •

u

( I + 9 . 5f)5/3

(2-18)(2-19)

Eqation 2-16 was obtaned verang results of measrements obtained atvarios heights above the grond and does not relect the dependence ofspectra on height Hoevr, the dependence of spectra on heiht is clearlsggested b Davenport [28 The spectral distribtion in he lower freqencrange has little influence on the strctral response However, the magnitdeof the trbulent fluctation components at the natural frequencies of thestructure (or of one or more of its maor elements) ma affect ts responsesignificantl Simiu [25 considered a wind velocit of 3 m/s and a srfaceroughness z = 8 m and compute the longitdinal spectra n the frequenrange of 1-5 Hz b sing Eqs 2-16 and 2-17 He considered heightsz = 1 m, 2 m, and 3 m The comparison showed that te expressioncurrentl sed in building codes overestimaed the longitudinal spectra oftrbulence in the higher freqenc range b as mch as 1%-4%To compare the spectra obtained sing Eqs 2-15 hrough 2-19, computations were made for two wind velocities namel U(z) = 4473 mph and U(z) = 9 mphat a height of z = 3 ft This height was chosen to conform to thereqirement of the ANS code igure 2-1 shows the longitdinal spectracomputed b Eqs 2-15, 2-16, and 2-17 for wind velocit U = 4473 mph (2m/s) The building code spectra overestimate the Kaimal spectra in thefrequenc range of 7-8 Hz and nderestimate beond the freqenc n = 8 Hz igure 2-11 shows the longitdinal, lateral, and vertical spectra of turbulence of 44 73-mph wind at a height of 3 ft At frequenc n = 1 Hz, the local isotrop is realized or freqenc less than 1 Hz,the vertical spectral energ content s less than these for the longitudinaland lateral coponents igure 2-12 shows the energ spectra of turblencefor a 9-mph wind at an elevation of 3 ft

21



E:«:0

0el;

0

0E

I nert ial subrange Kaimal et al .A ANSI A58.1 (1982)

447 m p h(2 m/s)

Z! t(9 1 4 m )

1.

0.001 0.01 0 . 1 0 1 .00Fequency, n

igu 2-10 giui buc SpcU = 44.7 3 mph m / s

E q - 7

n S" Z n )

U E 8

n S n

U E q

U = 4473 m

ms = ft

( 9 1 4 m

0.00L.

Frequency n (Hz)

igu 21 1 ubu Wi SpcU = 44.7 3 mph m / s

<g

TR6



s=

!

�•

�

0> 0E

n S (z , n )

:

n Sw ( z , n )

( 982)

,

n Sv (z, n )U = 90 .0 mph

(4024 m/s) :

Frequency, n (Hz)

ig 2-1 2 ubun Wn Spc U = 90 0 mph 40 4 m/s

2 RITION I WN LE OM E ORIZT

TR69

The vert ica wind components uctuate randomy at var ious rate s When the

heiostats are stowed in a horizonta position the eect o the ongitudinacomponent o the wind ve oci ty on the ei os as is reat ivey sma However , the pea ange o aac o he ver ica turbuent coponent o windveoc ity may have a s igni icant eect on the st ructure Te ange o attacst ipu ated in the ANSI code is rather arge According to the code theminimum ange o attac on a at pate must be 10

The methodoogy deveoped by Danies [9 } is used to estimate he probabevaue o the pea ange o attac on the heiosta in the horizonta positi on Accordg to Danie s the atera spectra are the bas is or determiningthe atera ange o at tac S ince the vert ica spectra energy conten isgeneray es s than that o the atera s pect ra Danie s suggest s that the

ange o attac wi give correc vaues a requencies beyond n = 3 0 Hz iit is determined on the bas is o the atera spect ra The ange o at acwi e somewhat overestimated or vaues o requency ess than n = 3.0 Hz Accordingy , the anges o attac or wind veoc it ies o 30 0 , 50 0 , and90 . 0 mph at an eevati on o 30 . 0 t are es imated First we determine theange o at tac or the atera compone o turbuent veoci ty Then ycomparing the magnitude o the atera and vertica spectra at their pea requencies , we use a correct ion actor to e st imate the ange o attac or thevertica component o the turbuent veocity

3



=�• '*TR2169

'

The angwind pecra are repreened by the re marked "ngidina , " andacrwind pecra are repreened by the cre marked "atera " Thengitdina and aera pctra ae S(w) at a reqency and height zare gien in the rm a dimenine rma :

where

and

S() c1 /m = (220)

u; { I1 + 1s (/m)2 J 5/3 }2

wz U(z) '

= 3 z/z )Cm r

=

czr

0 Uzu = •* Zr1n - z

Danie ' et pcra r rng wind cndi in are h in Figre 213

n he abe eqain zr i the reerence height eqa 60 t (183 m) rthe ie and the ae he ntan ggeted (hwn in Tabe 29 ) ; z0

0.01

-----�------__

_

0001 001 0 1 1 0

Figur 2-13 Srong Vin lociy SpcraSrce e 29.

2

10 0



able 29 Dimensonless nstants or ngitnal anteral Urblence Specta

Cnditin

tng wind(Lngitudinal)

tng wind( Lateal)

c

9 8

3 9 5 4

nstant

c2 c3

845 3

7 8

- ·

·-

uce : e 29

c4 c5 3

5 8 3 5

T29

ce ghness at the site is a stability paamete depending nthe atmspheic stability; U( z) is the mean lngitudinal wind speed at aheight z; and c , c2 , c3 , c4 and c5 ae dimensinless stespeciic cnstants The paametes and m accunt height eects and ae used innmalizing the dimensinless quantities

() c 3and u m

The llwing paametes ae equied t estimate the angle attack thelateal cmpnent the tubulent luc tuat ing velci ty the elevati n Z , themean lngitudinal wind speed U ( z ) at that height , and the chaacte is ticughness length z the s it e Us ing the elat ins given in Eq 22 thevalues the paametes ' U* ' and m ae cp te T est imate the ampli tude the lateal cmpnent tubulent velcity v , a simple sinusidal

mdel is used t can be assumed that·

v( t ) v sin 2t '

whee

v amplitude lateal velcity

eqency in Hz

t time ( s )

( 22 }

The equencies lwequency spectum analysis ae in the ange Hz The peak eqency is appximately Hz and is used tcalcul ate the nmali zed equency The nmalized equency paamete m n the abscissa Figue 23 is then cmputed and Figue 23 is

used t get the value w

m the diate F stng wind cndit ins ,uthe stability paamete vaishes and is neglected in evaluating the ictin velcity U*

t can be shwn 8 ] that at a paticula equency ,

25



5�1 ".

S ( 2I v< > 1 2d

Usng he reaon o v( rom Eq 2-2 Eq 2 can be reduced o

v 2S (

2

TR9

2-2

( 2-23

Equa on 2-23 s us ed o es mae he magn ude o pea aera veoc y

( 2-4

The ange o aac v or aera ucuang veocy s obane rom heoowng rea onshp

I,

v

o

v an

U( z � · 2-25

S ce he agnude o aera spec ra s approxmaey mes arger anha o he ver ca spe cra he amp ude o er ca ucua ng veoc y

s apprmae equa 0 9 v e age o a ac o he vecacompone o ucuaon s gve by

-w an

0 9 v

) U( z

( 2-2

The anges o aac o aera ad verca componens o ucuangeoces ave been compue or each o hree ean oguna veoceso 30 0 50 0 and 90 0 mph a he sandard eevaon o 30 0 or varoussurace roughnes s enghs The resu s are abuaed n Tabes 2- 0 and 2- and sho graphcay Fgures 2-4 2-5 When he surace roughnesseng z o a s e s sma he vaues o he ange o aac are reavey

es s The vaues ncrease as he roughness eng ncreases One neres geaure o he presen anays s s ha hen he mean wnd speed ncre s he vaues o he ange o a ac decrease The de s gn ange o aac

Tle 2-10 ition o le o Attck ue to luctuting Ltel elocty

Ange o Aac

Roughness(deg

He gh zU( 30 3 0 0 mph U( 30 50 0 mph U( 30 90 0 mph

0 0 (0 0 3 m 4 . 53 4 4 4 4 5

0 20 ( 0 0 6 m 4 03 9 3 96 3 7 0

0 40 (0 2 3 m 5 4 5 0 5 4 7 2

3 2 ( 0 4 m 6 7 3 6 6 6 9

968 (0 6 0 m 7 5 2 7 . 37 6 9 0

2 624 ( 0 8 0 m 7 5 3

26



TR-2169

Tae 2- aa le Aa ue uua ea ely

- -

-·

oughnessHeiht ,

z

Ange of ttack, w(deg)

. -

U ( 3 ) mp (3) 5 h ( 3) = h ·

1 t ( 3 1 m 368 3 6 337

2 t ( 6 2 m 4 1 2 4 4 3

4 ft ( 1 2 3 m 4 6 4 6 43

1 3 1 2 ft ( � m 6 1 3 6 2 64

1 6 ft (6 ) 6 6 1 6 2

264 t ( m) 6 8 6

suggested by te NSI 1-1 code is 1° c lmpoved vaue ofte ane attack suges ted by Murpy [ 14 ] is 6°

The McDonne Douas stronaut ics Coany ( MC) [ 3] repor ted tat a aiuo a 6 ° ae ck coud be expected or i winds i gente ro interrain wit a rouhness ent o 4

Vann [ 3 1 ] used Danie ' s aroac and et ated te ane of attack due toatera utuations for wind eocity = 3 ( 13 41 m/s ) at heigtz = 3 ft for surface rouhness z 3 f He cos dered te atera sectra as reresent ati ve of vert ica sec tra The es ti ated pea ane o at tac

1 0 . 0

80O<"

7 0

: 60i

0 50�c< 40

30

20

ue 214

0

- - - - - - - - - - - - -

0 1

Pea e

U (300 ) = 300 mph

U (300 ft) 900 mph

03 0 4 0 5 0 6 0 7 0 8 0 9 1 0Roughness height (m)

Aa ue Tue ea ey

2



O

-0�O\ <

TR-2

U (30.0 ft) 500 mph

90.0 mph

Figure 5 Peak le o Attack ue to bulent etical locty

w z s 9° Th surfac rouhnss z of 3 ft s ratroo r Th surfc rouhns s vau s a sn f cant rat r n thrnn f h an of attac u to urbut voc t s Thvaus f h an of tac ncras as h surfc rouhnssncrs s On nrs n fatur o f th rs nt any ss s that h vau

f h n f c crss th th ncras of th n n s Fur 2- shs h for 2 z < 4 th s t a a an ofc u o urbun vrtc vcty for -h n an hostas or n hrz ont os on s n th ran of 4 °- ° Est atn h n of tc s qut nvov To obta n or r b vaus forh n of tc rurs shou b tan to thr fu-sca f stuyor o suy n sut fo fd n th nvr onna n tunn

u n cnn [ 2 Tb 22 ] v ty ca vus of surfac rouhnssz fr vrous ys f surfacs an corrsonn vus of th surfac rac ff c ns Th b so ncus h sus vus of z for but-urrns such s ousrt s of tons an suburbs cntrs of tns cntrs ofr c s c Th sust vau of z

for utsrts of tons n

suburbs s n h rn of 2- 4 ; for th on fs , z s n thrn f . • - nn on th hys c characr s cs Fur 2-sos h fr 2 z 4 th sa an of tc for -hn n s s o n horzont s on s n th ran of4 . °- 5 . ° f h or z vaus ar us for th ho sa t f thvus f h n f t tac ar sar ur 2- 4 an ur 2- shocry h A c vus for h an of attac r too hh

2



R-29

SEIO 30

IO O WN I

Rt t 5 2 , 2 2 , 32] o ale model o olar olletor iromtl tl how that the preet method o detrmiig widloa l ll t , photooltai array a hel o ta uig thl tl i th AN I A58 - 9 82 bui l ig od reqiremet ormimum loa builig ad ohr trutur 2] i oeratih o th aalabl irmatio iiate that h dgr o oertm iiat bt th tal ett o that oeratim

·mt be a i

mo tal . h a ot deeloped or the lo-height t ruture like \la ol lto . h prtiet ite pei i meteorologial data uh ai loi t it bto i the lo atmophere , tabil it eature adtblt hratt the id eld r iably k S i thei pol hag 2 5 ] th the hag o the roughe lgth o the

lalt th tt, alu epedig olely o the airport dta hoult b optmm ig ithout arull oiderig the terrai oi t o ll rae oghe , oitatio o the heiot at , ad di rt oo th .

R t 3 ] eelpd a iteretig methodology to etermie the i la trture baed o the tatital paramter o thel tm mmm p th aual maimum id peed , a the daly maimm w p . Rra t al ue the geeral eqa ti o or deteri thi p a or al the parameter (pre ure oei iet t ielot p, loty preure oeiiet that deped o the type opo hht bo th groud , gu t at r that deped o the repoeht t i th trt ur , ad the bai wid peed maurd at the hht) a raom ariable he mea wid pre ure d oe i i t t th preure are eprd a tio o the mea th it ara tio o th radom ariabl Laborato tet eul t t obta l o oeiiet ariatio

rall th tt i id di ret io are ot oi dre i the ode pt ] o two a o loadi : ( ) th dirtio o maimum i iml trbutd bte ad , orrepig to theampt tht th t rpo our o matter what the id dirti a ( 2) th ito o maimum wid i ditributed aordig to a oiel. h t o th moe i a 2 to the mode alue i ae , lld the t i to ator , ha be et imated to b 0 2 Raira t

l. ] or othr ato , uh a eriebi li ty ad ult imate limit tt , omm tht th m d ig wid pre ure b rue by a de ir i ta t . 5 Rig the wid load by 25% or the ariabil to i d t o oth o ider tio hould b ieed ith ut io .Rult rom mlt lboratory or ield tuie hld be e to etmatthe ruio o loa aed by the aritio i wid dirtio

oiatio th h layer tat deelop oer the hliotat urae i aara ty that ma ld to the redutio o drag eperieed by thehlotat. lbo 35 ] ad Grthore 3 ] ob ered that the mall-ale

29



5�· /·=< � #

-1

trbece icreases siificaty i the reattachi shear ayers o the srace ad coseqety icreaes the aitde of the hih eate srfaceres sre It is reasoabe to cosi der that eti the rei o of searaedfow ad its sbseqet reattachet ay be sef i redci the aitdeof eatie res sre Mebore [ 35 obsered that eti the searated fow

reio redced the eatie ressre thereby eadi to creased fowstabiity It s we kow that a ressre redctio (beow abiet ) o thestreawise srfaces ear the eadi ede of the fat ate occrs i therei o of fow searati o Veti or itrodc i fid wi th a hiher eeof oet i the reio (the bbbe der the reattachi shear ayer ) is aod techiqe to deay fow searatio ad decrease the redced ressre

,effe ct his ca be accoi shed by s i a so tte d eae ao the er iheryof the srfac

he heios ta t odes hae shar edes ad der rear ad hori ota stowositios fow searatios ear the eadi ede ad sbseqet reattahetoccr oros eae arod the edes of the scae ode of a ode wod besef for testi i a eroeta wid te der siated fow cod it ios St reaii the widward ad eeward edes ay be hef redci ad ee eiiati fow searatio ad sbseqet reattachet

he air a betwee the odes aows hih-oet air to fow throh thearray ad is exected o redce the widward ressre as we as the eatieres sre o the back side he aro riat e aot of air a for tota draredctio eeds to be deteried fro aboratory tests i the satedf Iestiatios of the effects of hih orosity i a fat ate theredctio of tota dra ay ead to basic kowede of dra cotro byaowi hih-oet fid i the wakes of a fat ate he te st res tsof Xerikos et a [ did ot show siificat dra redctio becase thesot oeis were rather sa reiiary stdy of the effects of the

soidity ratio of a at ate ace ora to the fow i the bodary ayerby awaa ad Hady [ 3 showed th cosiderabe redctio i dra is ossibe whe the soidity ratio is ess tha 0%

Exerieta rests fro the wid te stdy [ idicated hat aciheiostats i the wakes of the heiostats i frot heed redce wid oadso the heios tats i the wakes Howeer wid di rectios tbetitesity ad dyaic resose of the strctre de to icreased trbecei the wake reios ay ifece the et otcoe I the s iated fowf ie ds i the wid te we eed to st dy the deeoet of wakes behidhe heiostats i the ier art of the fied to ai kowede of the reatie aitde of the force ad oet coefficiets that are eeded to

adeqatey est iate the wid oad o a hei ostat Perieter feces [ 38 are effectie i redci wid oads o the hotootaicarrays ece oros i ty of 30-50 ad fece heiht aroxiatey eqa tothree-qa rte rs of the ar ray heiht ehace · the redc ti o of wid oads s iif icaty Howeer the effect is oy iited to the first few rows ofarrays ao the eriet er eces is ide the he os tat fied aced atexerietay deteried stra tei c os it ios ay be he f to redce thebase-bedi oet of the he iost at

30



s l u

�

'

�

�

-

TR-29

he eerea wrks f Raa e a [ 39 40] wh arac rugh sarce rs are f grea racc race he s g fca er ereceefec re he usrea cec he aera a f rcescaes ha s cecr ues wh a arra exerece rce reuc Raa e a hae s ue he uece e hegh a ece

ace hre aerure whs us rea f he rs rw c ecrs The ul s cae ha a ece hegh sewha ess ha he fu c o hegh res he aj r ar f he frce reu ar resu sare a s a e r he uece f he er hegh

he e r e s ae u rees shrus a her sa sruc ures acg as w rears a h ereer f he hesa fe a e heu reuc he e ec e w ec he fe urrck [ 4 ] sereha rr esge hetr s a w arrers cu e scae ec reucg w a s • es s sse su aeauae he e ec eess f he arrer he w ue

The ackg es [4] hess th e ha scere eec he reu as Hgher ack y reuce e w a he he s as h e e e ee a u es hehesa e wh reae hgher e n ou ar f he f e

The hesas t� J her he e are sujece axuw a herefre he shu e esge rura rer a re s ss e use ess r a rea e he u srcure fr he hess n th rr f he e

31



R-9

SEION 4

NSION RETIONS

hi tdy a limitd to riig ad aig th prt digmthodology or id loadig o olar olltor partilarly or hlio tat ad rommdig ara o rthr itigatio to dlop raliti ritriaor dtrmiig adqate id load h rlt ad ol io o th tdya b mmari zd a ollo

h prt mthodology or digig id loa ig th otli giby th NS A8 - 98 Cod i orati

• h hitory o th itpii loity data i ary to applytrm al ordr tatiti or dtrmiig dig id pd Loallimatalogial data ildig id dirtio ad ra roghhold b d to dlop th loity proil

• Comparati tdy o th total or oiit o a lat plat oario apt ratio ad at ario agl o attak ho that thal obtaid by uig th ANS Cod ar alay highr

• h rgy ptra obtaid by th ormla ggtd by arioathoriti r ompard ith th rgy ptra or th od ad hothat i th lo-rqy domai th o ortimat ptral alor lor rqi bt drtimat i th rgio o highr rqi ildig th atral rqi o hlio tat ad othr olarolltor

• h gl o attak that rlt rom th ltatig rtial id ioidrably mallr tha th al ggtd by th od

• lopmt o loally modiid lo or th hliotat ha th pottialto rd id load o th hl io tat

• Appropriat tilatio i th hliotat modl ha th pottial tord dyami id load

Rommdatio or rthr tdi that might rd id loadig o th olltor ar tatd brily

• odiyig th lo loally by ig a trl timlator i th ormo poro a arod th hliotat ill diorag th lo paratioat th dg o th hliot at ad hlp to rd dyami id load

• tigatig th t o appropriat gap bt th modl illorag ti lat io arod th modl

• Stdyig th t o th primtr ad i th ildarod a grop o hliotat zo ill b l i orall id-loadrdtio

• lopig a id ro or th hliotat ild to timat th tatitio ariat o o id di rt io h t rrai ad topographial apt oth hliotat ild play importat loal rol i dtrmiig th magitd o id pd ad dirtio h id dir t io i ot oid rd

32



R-29

i e builig oe . e tat ti o te i etoal aiabil ity ote i ae eetal etemiig i loa elably

33



5' -�· .- � f

TR69

SEION 5

REENES

1 Pugsley , , "The Safety of Structures , " Baltimore MD dward old ,1966

avenport , G , "st imat ion of Repeated Loads on Structures with pplicat ion to Wind nduced Fatigue and Overload , " Proceedings of RLM nternational Sympos ium ffects of Repeated Loading of Materials and St ruc-

3

tures , Vol 38 , 196 ·'

Robertso , L , "On Tall Buildings "Proc dings

of a Symposium on Tall.�-

Build ings , Univ rs ity of Southhampt on , di t d by A Coull and B

Stafford-Smith , Oxford , U K Pergamon Press 196

4 Davenport , G , "The Dependence of Wind Loads on Mete orological Para

meters , " Proceedings of nternational Research Seminar on Wind ffects onBuil dings and Structures , Ottawa Nati onal Research Counci l of anada ,196

5 Davenport , G , "The Nature of Dis turbing orces , " Proceedings o RMnternational Symposium ffects of Repeated Loading of Materals andStructures, Mexico, 1966

6 Velloz zi , J , and Cohen, "Gust Response Factors " Journal of theSt ructural Divis ion, mer ican Soci ety of Civil ngineers , Vol 94 , ST 6 ,June 19 68

Davenort , G , " Rationale for Determination of Design WindVelocit ies , " J Structural Division, merican Society of Civil ngieers ,Vol 86 , No ST 5 , Proc Paper 246 , May 196 0

8 Gumbel , J , "S tat it ical Theory of xtreme Values and Some Practicalppli cations , " pplied Mathematics Serie s No 33 , Washington , DCNational Bureau of Standards , 19 54

9 Tho, H C S , "Frequency of Maximum Wind Speeds , " Proc Separate No 539 , mer ican Soc iety of Civil ngineers , Vol 8 0 , November 19 54

10 Lieblein , J , "Method of alyzing treme Value Data , " Technical Note3053 , Washington, DC Nati onal dvisory Commit tee for eronaut ics , 1 954

1 1 Tho, H C S , "New Distribut ion of xtreme Winds in the United States , "J merican Society of ivil ngineers , Vol 94 , No ST , July 1968

12 merican Nati onal St andard 58 !Bui lding Code Requirements for MnimumDes ign Loads in Build ings and Other Structures , NY merican NationalStandard nst itute , 1982

1 3 Simiu , , "Wind Climate and Failure Risks " J Structural Divis ion ,merican Socie ty of Civil ngineers , Vol 102 , ST 9 , September 1 96

34



14

1 5

16

1

18

1 9

TR2169

Murpy L M An Asse ssment of xist ing Studies of Wind Loading onSolar Collectors SRI/TR63 281 2 Golden CO: Solar nergy ResearcInstitute February 1981

Roscke J Wind Loading on Solar Concentrators : Some General Con

s iderations /JPL1 06 066 JPL Publicat ion 831 01 Pasadena CA : JetPropuls ion Laboratory May 198 4

Peglow S G Wind Tunnel Tes t of a Full Scale Hel iost at SAND 798034 Livermore CA : Sandia Laboratories June 19 79

Xerikos J t al Te Aerodynamics of Heliostats for Solar Power PlantAppl icat ions Proceedings of te 5t Internat ional Conference on Windnginees 1 979 2 vols edi ted by J Cermak Oxford U K : PergamonPress 1980

McDonald J R Wind ffect s n Solar Tower Generato r Lubbock TX:Inst itute for Disas ter Researc Texas Tec Univers ity 19 78

Cermak J Appli cat ions of Flui d Mecanic s to Wind ngineerngAFreeman Scolar Lecture J Fluid ngineering Vol 9 7 Marc 1 9 5

20 Baduri S S imulat ion of Urban Atmospere for Diffus ion Study ngineer Vol VI No 2 1973

2 1 Lindsay J Force and Pressure Tes ts of Solar Collec tor Models in teVougt Corporat ion Systems Divis ion Low Speed Wind Tunnel SAND 7670 07 Albuquerque NM : Sandia Laboratorie s May 19 79

22 Randall D D D McBrde and R Tate Parbolic Troug Solar

Collector Wind Loadng SAND 7980 34 Albuquerque NM: SandiaLaborator ies June 1 979

23 Task Committee on Wind Forces Wind Forces on St ructures Transacti ons Amer ican Soc iety of Civil ngineers Vol 126 No 326 9 19 6 1

24 S imiu Wind Spectra and Dynamic along Wind Res ponse J StructuralDivis ion American Soci ety of Civ il ngineers ol 100 No ST9 September 1974

25 Simiu and R H Scanlan Wind ffects on Structures NY Jon Wileyand S ons 19 78

26 Kaimal J C et al Spectral Caracterist ics of SurfaceLayer Turbulence J Royal Meteorological Society Vol 8 196 1

2 Lumley J L and H A Panofsky Te Structure of Atmospeic Turbulence Jon Wiley & Sons 19 64

8 Davenport A G Te Spectrum of oriontal Gustiness Near te Groundin Hig Winds J Royal Meteorological Society Vol 8 7 196 1

35



TR2169

29 Daniels , G E , d , Terrest rial Environment Climati) Criteri Guidel ines for Use in Aerospae Veile Development , 19 73 Revis io, NASA 647 57 , Huntsvi lle , AL arshall Spae Flight Center, 197 3

30 Donnell Douglas Ast ronautis Company , Opt imi zat ion of the SeondGeneration Heliostat and S pei iation, SAND 82818 1 , ay 1982

3 1 Vann , P , ind Effe ts on Solar Tower Generators , Fi nal Report ,Subontrat No 77 TT1 ( SubTask b ) , Lubbok , T Energy Foundat ion ofTexas , Texas Teh Universi ty, 19 78

32 Behtel Nat ional , In ind Desi gns on Flat Panel Photovolt ai ArrayStru turs , SAND 79 7057 , Livermore CA Sandia Laboratorie s 1980

33 Ravindra , K , et al , ind and Snow Load Fators for Use in Load andResitane Fator Design, J Strutural Divis ion merian Soiety ofCivil Enginers, Vol 104 , ST 9 , 1978

34 Davenport , A G , The Pred it ion of Risk under ind Loading , Pro ofthe Seond Inteati onal Conferene on St rutural Saf ety and Reliabi li ty ,Tehnial University in unih, unih, est Germany, Dusseldorf, estGermany eerVerlag , Sept ember 19 7 7

35 elboue , H , Turbulene Effets on aximum Surfae Pressu resAehani sm and Pos sib il ity of Load Redution , Proeedings of the FifthInte rnat ional Conferene on ind Engineering , F

.

Collins , CO ColoradoState Univesity, July 1979

36 Gartshore , I S , The Effets of FreeStream Turbulene on Drag ofRetangular TwoDimensional Prisms , Bounda Layer in Tunnel , Report

73 , Canada Univers ity of es tern Ontario, 197 3

37 Rangwala, S , and E Handy, Drag of a Flat Plate of Vaiable Soli dity Ratio Plaed Normal to Flow in a Boundary Layer , Proj et Report forE 350 6 , Advaned Fluid ehais I , El Pas o, T: ehanial and Industri al Engineering Department , Deember 198 3

38 artin arietta Corp , Heli os tat Field ind Effets Test s , SAN 204222 ,San Franiso , CA Department of Energy , February 19 79

39 Randall, D E , D D Bride , and R E Tate , S teadyState ind Loadingon Parabli Trough Solar Colletors , SAND 7921 34 , Albuquerque :Sandia National Laboratories, August 1980

40 Randal , D E , R E Tate , and D A Powers , perimental Results ofPithing oment Tests on ParaboliTrough SolarColletor Array Configurat ions , SAND 82 156 9 , Albuquerque , N Sandia NationalLaboratorie s Deember 198 2

4 1 Sturrok, J , Aerodynami Studies of Shelterbelt s in New Zealand , New Zealand Journal of Si ene , Vol 12 , No 4 , 196 9

6



R69

4. Pterka J. A. B . Bieniewi an J E Cermak TenialF sibilit

o Innovative Conepts or Avoiding or Reuing ind Loas on Conentrator Colletors Task I Report or Solar Energy Resear Inst itu te Fort Coll ins CO Colorado State Univers ity , ar 98 4

37



TR269

DISRBION LIS

Kosta chinSandia National Laboratories

Division 8473P O Box 969Livermore, C 94550

R kins , Ph D Professor, ngineering Science and

MechanicsVirginia Polyechnic nstitute and

State UniversityBlacksburg , V 2406 1

Don BartlettBoeing ngineering and Construction

CompanyMail Stop 942PO Box 3 707Seattle , W 98 125

David Blake, PhDngineering Managercurex Corporation485 Cyde venueMountain View, C 94042

Floyd Blake

RCO Ventures Company7061 South Universiy BlvdLittleton , O 8012 2

John Cerma, PhDProfes sor , Civil ngineeringept of Cvil ngineeringFluid Mech and Wind ng ProgramColorado State UniversityFort Col lins , CO 80 523

Bill Delemeter, PhD

Sandia National LaboratoriesDivision 8453PO Box 969Livermore, C 94550

William Dickhartssistant to the DirectorThe Budd CompanyFort Washington, P 19 034

38

Robert GervaisMcDonnel Douglas Company

5301 Bolsa venueHuntington Beach, C 92647

H Gerwin, PhDGerwin Research14305 stead RoadSilver Spring, MD 20904

Roger GilletteBoeing ngineering and Construction

CompanyPO Box 3707Seattle, W 981 25

Jim Leonard , Ph D Sandia National LaboratoriesDivision 6227P Box 5800lbuquerque , 8 7 1 1 5

John Lucas, PhDJet Propulsion Laboratory4800 Oak Grove DrivePasadena , C 94 10 3

Monte McGlaumLaJet Company3131 ntilly Roadbi lene , TX 796 05

Cayton MavisSandia National LaboratoriesDivision 8473PO Box 969Livermore, C 94550

Jon Peterka , Ph D

Professor, Civil ngineeringDept of Civil ngineeringFluid Mech and Wind ng ProgramColorado State UniversityFort Collins , CO 80 523

J T Pearson, PhDPurdue UniversityMechanical ngineering BuildingWest Lafayette , N 479 07



Tm Reinhold, PhDCenter for Building TechnologyNational Bureau of StandardsWashington , DC 202 034

Bob Reuter, PhDSandia National LaboratoriesDivision 1523PO Box 5800Albuquerque , NM 8 7 1 1 5

Jim Rogan, PhDMcDonnel Douglas Company5301 Bolsa AvenueHuntington Beach, CA 9 647

T W Rogers

United Sace Boosters2-EOPO Box 1626Huntsvil le , AL 3580 7

E J Roshke, PhDThe Jet Propulsion LaboratoryCalifornia Institute of Technology4800 Oak Grove DrivePasadena , CA 9 1 109

Aharon Roy

Head , Sol ar Power Laborato ryDepartment of Chemical EngineeringBen-Gurion University of NegevPO Box 653Beer-Sheva 84 10 5 , ISRAEL

Dan SallisDan-Ka Products790 UmatillaSuite 212Denver , CO 80 204

John Schaeffer, PhDManager of ProjectsProjects DepartmentAcurex Corporation485 Clyde AvenueMountain View , CA 94042

39

Martin ScheveDepartment of EnergyCE-31 4 , Room 5H-04 1Forrestal Building

TR-2169

10 00 Independence Avenue , S W

Washington, DC 20585

Jeff Shingleton49 Elm AvenueTakoma Park , M 20912

Jack Swearingen, Ph D Sandia National LaboratoriesDivision 8453PO Box 969Livermore, 94550

H ieman, PhDProfes sor , Engineering Science and

MechanicsVirgina Polytechnic Institute and

State UniversityBlacksburg , VA 2406 1

A ThomasInstrumentation and Services UnitIndian Institute of ScienceBangalore - 560-01 �INDIA

Kenell J Touryan, PhDVice Pres ident , R&DMt Moriah Trus t6200 Plateau DriveEnglewood , CO 80 1 1 1

Lee WeinsteinMcDonnel Douglas Company5301 Bolsa AenueHuntington Beach , CA 92 647

Frank WilkinsDepartment of EnergyCE-314, Room 5H-041Forrestal Building1000 Independence Avenue , S WWasington , DC 20585



Document Control .

SE Al Report No. Page ,

S

E

R

I

T

2

5

3

6

9

Title and Subtite

Wind loading on Soar Coectors

7 Author(s)S. Bhaduri and �- r . Murphy

9 Pefoming Oganization Name an AessSoar Energ Research Institute1617 Coe BouevardGo den , Co orado 8401

12 Sponsoing Oganizan Name an Aess

15 Suppementay Notes

16. Abstact (Limit: 2 wos)

1 2 NTIS Accession No. 3 Reciient's Accession No.

Pubication Date

June 19856.

8 Pefoming Oganization Rept No.

Poject/Task/Wok Unit No1384.30 nd 5 1 0 2 . 3 1

1 1 . Contact (C) o Gant {G) No.

{C)

(G).,

3 Type of Repot & Peio Covee

Techni cal eort

14

The present des i gn methodoog for the determi nati on of wi nd oad ing on theari ous soa r co ectors has been rei ewed and as sesse d . The tota force coeffi ci ents of f at pa tes of asect rati os 1 . 0 an 3 . 0 , especti �e , at arious anges of attack obtined b using the guideines of the ANSI A58.1-1982,hae been compared it those obtained b using the methodoog of the ASCTask Commi ttee , 1 961 , and the experimenta resu ts of the u -sca e test ofhe iostats b Peg ow . The turbu ent energ spectra , cur rent ep e i n thebui di ng code, are copared i th hoe of Ka ma ·t a . , Lum e , and onosfor in eoc es of 20 . 0 /s and 4 . 24 /s at an e eati on of 9 . 1 5 m . The ongi tuda spectra of the bui di ng code oerest imates the Kai ma spectra i nthe frequency range of 0 007 Hz - 0 . 8 H z an underestimates beond the fequen of 0 08 z The peak ang es of attack , on the he i ostat, stowed i nhorizonta posiion, due to turbuen ertica d aera omponents o wind:e oci t, have been est imted b u si g 'Dani e • s methodo og for three wie oci ti es and comared w i th the va ue sgge sted b the code . The experimentaresu s of a s imp e test i the bortr id icate the feas i bi i t of decres i ng the drag foces of the fat p te b reduci ng the so i d i t rat io

7 Dcument Anaysisa. Desciptos Dnami c loads ; He i ostat ; echani c S tructurs ; Soa r Co ectors ;Strees; Wind; Wind loads

b Ieiies/Open-Ene Tems

c. UC ategoies

62e

wind load on structure parabolic colector

Documents