experimental study of the neighborhood effects on the mean

Original Article

LatinAmericanJournalofSolidsandStructures,2018,15 3 ,e21

Experimentalstudyoftheneighborhoodeffectsonthemeanwindload‐ingovertwoequivalenthigh‐risebuildings

AbstractThispaperpresentsaseriesofresultswithrespecttothemeanvaluesofshear,basemomentandtorsionactinginabuildingobtainedthroughanex‐perimentalwindtunnelstudyusingthestandardbuildingproposedbytheCommonwealthAdvisoryAeronauticalResearchCouncil CAARC asbuild‐ingreference.Intheloadingdetermination,theinterferenceofaneighbor‐ingbuildingwithsimilargeometriccharacteristicstotheCAARCwassimu‐lated,consideringvariationsofpositioningandspacinginrelationtotheref‐erencebuilding.Itwasconcludedthatthepresenceoftheneighboringbuild‐ingincreasedthemeanloadsinthereferencebuildingforasignificantnum‐berofdirectionsconsidered.Inthecaseoftheconsidereddeviationsandtheproposedprovisionsbythisstudy,itwasconcludedthatthevicinityfactorthatwould contemplate themajority of the results obtained in the testsshouldincreasethewindloadsbyatleast60%inrelationtothevaluesob‐tainedforthebuildingreferenceconsideredinisolation.

Keywordsvicinityeffect;windaction;buildingaerodynamics.

1INTRODUCTION

Theconstructionoftallbuildingsisverycommoninlargeurbanareas.Amongthereasonsforthispractice,thegreateruseofurbanareaiscertainlyoneofthedeterminingfactors.

Inthesearchforlessvaluableland,manyenterprisesarebuiltfartherawayfromthedenselybuiltmetropoli‐tanareas.Inmanycases,suchbuildingsareuniqueintheirregions,butwiththeconsequentlocaldevelopment,morebuildingsofsimilarsizebegintobeerected.Theresultofthisisachangethewindflowintheregionandthechangefromanisolatedbuildingsituationtoasetofbuildings.

Theinterferenceofhigh‐risebuildingsinteractioneffectshasbeenasubjectofseveralresearchers’studiesfordecades.ItcanbesaidthatthesestudiesbeganwiththeevaluationoftheeffectsattheEmpireStateBuildinginNewYorkduetotheconstructionoftwonearbybuildingsbyHarris 1934 .Fromthisstudy,manyresearchesonthe interferenceof neighboring constructionshavebeenmade MelbourneandSharp, 1977;Blessmann, 1985,1992,Thepmongkornetal.,2002,TangandKwok,2004,Lametal.,2008and2011,Kimetal.,2015a,b .Inadditiontoexperimentalandmeasurementstudiesinrealbuildings,manyresearchershavedevelopednumericalsimula‐tionsoftheseeffects TutarandOguz,2002,Blockenetal.,2007,Janaetal.,2015 .Kimetal 2015b pointoutthatestablishingaguidelinetoevaluateinterferingwindloads,whetherglobalorlocal,isanextremelycomplexprob‐lembecauseofthelargenumberofvariablesinvolved.Thus,oneofthegreatchallengesoftheseresearchersistoworktheeffectsoftheseinterferencesinacomputationalwayandtrytoadequatelyrepresenttherealsituation.

Searchingtomeetthestructuralandnormativeconceptions,moststudiesseektoestablishguidelinesinordertodeterminetheeffectsofinterferenceofneighboringbuildingsonthewindloadingsandtheresponsesproducedinthebuildingstodeterminethestructuralparameterstobeconsidered.Ingeneral,theparametersusedincodesandstandardsdetermine limitingconditionssuchas thedirectionofwind incidenceandheightofneighboringbuildings.Asanexample,theEurocode1:2010‐Part1‐4:GeneralActions,WindActions,ofInstitutoPortuguêsdaQualidade 2010 ,whichrecommendsconsideringtheinfluenceofneighboringconstructionsinthedetermination

GregorioSandroVieiraa*JoséLuisVitaldeBritobAcirMércioLoredo‐Souzac

aUniversidadeFederaldeUberlândia,FaculdadedeEngenhariaCivil,Uberlândia,MG,Brasil.E‐mail:[email protected]ília,ProgramadePós‐GraduaçãoemEstruturaseConstruçãoCivil,Brasília,DF,Brasil.E‐mail:[email protected],La‐boratóriodeAerodinâmicadasConstruções,PortoAlegre,RS,Brasil.E‐mail:[email protected]

*Correspondingauthor

http://dx.doi.org/10.1590/1679-78253560

Received:November28,2016InRevisedForm:September11,2017Accepted:October16,2017Availableonline:February02,2018

GregorioSandroVieiraetal.Experimentalstudyoftheneighborhoodeffectsonthemeanwindloadingovertwoequivalenthigh‐risebuildings

LatinAmericanJournalofSolidsandStructures,2018,15 3 ,e21 2/15

oftheaveragewindinordertoverifytheeffectoftheturbulenceincreaseinthewakeofthesebuildings.InitsAnnexA.4,thiscodepresentsaconservativeproceduretodeterminethewindspeedbasedontheheightoftheneighboringbuilding,analyzingparameterssuchastheheightofthebuildingunderstudyanditssmallercross‐sectionaldimension.

Inordertoincreaseknowledgeregardingtheinterferenceofneighboringbuildingsintheactionofthewindonanotherbuilding,thepresentstudyinvestigatedtheeffectsoftheinterferenceofaneighboringbuilding,withidenticalgeometriccharacteristicstothebuildingunderstudy,ontheresultingmeanforcesinthedirectionsoftheXandYaxes,basemomentaroundtheXandYaxesandtorsionaroundtheaxisofthebuildingunderstudy.Forthedatacollection,thevariationofthewindincidencewasperformedfrom0o‐345o,withincrementsof15o.Inadditiontothewinddirection,thedistancefromtheneighboringbuildingwasvariedconsideringfourcontoursofdistancesandthreealignmentsbetweenedificationinstudyandneighboringbuilding.Thediscussionoftheresultsispre‐sentedthroughgraphicsthatrepresenttheaerodynamiccoefficientsforeachoneofthestudiedloadingmecha‐nismscomparingtheresultsofthebuildingconsideredinisolationwiththebuildingsubjecttotheinterferenceofaneighbor.Forapossiblecomparisonwithresultsofotherresearchers,thegeometryofthebuildingsfollowedthesameproposalstandardizedbytheCommonwealthAdvisoryAeronauticalResearchCouncil CAARC .

2EXPERIMENTALPROGRAM

2.1Simulationofthenaturalwind

TheexperimentalprogramwasdevelopedattheLaboratóriodeAerodinâmicadasConstruções BuildingAer‐odynamicsLaboratory oftheUniversidadeFederaldoRioGrandedoSul FederalUniversityofRioGrandedoSul ,herein identified by LAC‐UFRGS, located in the city of Porto Alegre, Brazil. The testswere performed at Prof.JoaquimBlessmannboundarylayerwindtunnel.Thistunnelhastwotestsectionswithdimensions1.30mx0.90mx9.32mand2.50mx2.10mx12.00m,beingsuitableforthecorrectsimulationoftheatmosphericlayerwherethebuildingsaretested Blessmann,1990 .A1:406scalemodelwasbuiltandaboundarylayerwindflowwassimu‐latedwiththecharacteristicsindicatedinFigure1.

2.2Detailsofmodelandinstrumentation

Twobuildingswereconsidered.Theinstrumentedmodelwasnamedthemainbuildingandtheotherneigh‐boringbuildingwasnamedthemutemodel,bothwithidenticaltransversalsectionandheightinscaletothemodelproposedbyCAARC.Considering thescale factor, thereducedmodelsused in the testhadacrosssectionwith75mmx112mmandaheightof450mm.Themainbuildinghadatotalof280pressuretapsspreadovertenverticallevels.Ateachlevelsevenpressuretapswerearrangedperfaceofthebuilding,ascanbeobservedinFigure2.Figure3showsthedifferentpositionsofthemutemodel,aswellasthedeviationsconsideredinthisstudy.Threealignmentshavebeendetermined,withalignmentV1coincidingwiththeYdirectionofthemainbuilding,align‐mentV2isparalleltothediagonalofthemainbuildingbutdisplacedsothatitsprojectioninthisdirectiondoesnotoverlapthemainbuilding.Finally,thealignmentV3hasthesamedirectionasthediagonalofthemainbuildinganditisalignedtoit.Inadditiontothesealignmentsspacingswereestablisheddirectlyrelatedtotheheightofthemainbuilding.EachspacingcorrespondedtothedistancebetweenthecenterofthestudybuildingandtheboundaryoftheoutlineofacirclewhosediameterwascalculatedbyreferencetotheheightHofthemainbuilding.Intotal,fourcontourswithdiametersof1.0H,1.5H,2.0Hand2.5H,denominatedbyD1,D2,D3andD4respectively.Theneigh‐boringbuildingwaspositioned,foreachalignment,inalocationimmediatelyoutsideeachcontour,totalingtwelvedistinctvicinities,threeforeachcontour.Foreachvicinity,twenty‐fourwindincidenceswereconsidered,startingwiththe0odirectionandvarying15ofromthereuntilcompletingaturnat345o,resultinginatotalof288casestudies.



Figure1:Characteristicsofthesimulatedboundarylayerwind,withvelocityprofilepowerlawexponentp 0.23

Figure2:Equivalentfull‐scaledistributionofthepressuretapsintheCAARCbuilding unit:m

Figure3:Indicationofthepositioningoftheneighboringbuildinginthecoordinatesystemoftheexperiment

2.3DefinitionoftheForce,BaseMomentsandTorsionCoefficients

AMANOAIR500Schiltknechtelectronicmanometer,withresolutionof0.1Paandaccuracyof0.2Pawasusedtomeasuretemperatureandpressureinsidethetestchamberatthetimeoftheexperiment.InordertoobtaintheinstantaneouspressuresaScanivalveTypeZOC33‐Dantecsimultaneoustypefloatingacquisitionequipmentatanacquisitionrateof20kHzandimprecisionof0.12%wasadopted.Foreachwinddirectionandforeachtapoverthesurfaceofthemodel,8192pressurereadings,inmmH2O,wereperformedinarangeof16s.SomepicturesoftheequipmentareshowninFigure4.Fromthesepressuretimeseries,onlythemeanvaluesarepresentedinthiswork.Theaveragevaluesweredividedbytheaveragedynamicpressureintheperiodofthereadings,thusobtainingthedimensionlesspressurecoefficients.



Figure4:Datareadingequipment: a Manoairandhosesconnectingtothefeetometricrings; b Scanivalvewith64

channelsofpressuremeasurementpermodule.

Theresultingforcecoefficientsinthedirectionofthemainaxeswascalculatedaccordingtoforcesactingontheareaofinfluenceofeachpressuretake,bytheproductofthedynamicpressurebythetotalareaofthewindface,Accordingtoexpressions1and2:

x

xF

y

FC

qB H 1

y

yF

x

FC

qB H 2

Atwhere:• Fx, Fy: global force in the direction of the X and Y axes; • CFx, CFy: coefficient of force in the direction of the X and Y axes; • q: dynamic wind pressure; • Bx, By: nominal dimensions of the transversal section of the building; • H: height of the building.

ThebendingmomentcoefficientsaroundtheXandYaxesweredeterminedaccordingexpressions3and4:

x

xM

x y

MC

qB B H 3

y

yM

x y

MC

qB B H 4

Atwhere:• Mx, My: Moment of flexion around the main axes X and Y; • CMx, CMy: Coefficient of flexion around the principal axes X and Y;

Torsionofthecoefficientaroundverticalmainbuildingaxisisindicatedinexpression5:

TT

x y

MC

qB B H 5

Atwhere:• MT: Torque moment around the torsion axis; • CT: Coefficient of torsion;

2.4VicinityFactor

AwaytoquantifytheinterferenceofabuildingonitsneighborwasthroughtheVicinityFactor FV .Withthevaluesofthepressurecoefficientscalculatedaccordingtotheexpressionsofthepreviousitem,theFViscalculatedastheratiobetweenthecoefficientfoundconsideringthepresenceoftheneighboringbuildingandthecoefficientconsideringtheisolatedbuilding,asshowninexpression6:



with neighborhood

isolated

CFV

C 6

Atwhere:• C: Aerodynamic coefficient under study; • FV: Vicinity Factor

3RESULTSANDDISCUSSIONS

Inordertohaveaparametertocomparewiththeresultsobtainedinthisresearch,thelimitsestablishedbytheBrazilianCodeNBR6123:1988,ofAssociaçãoBrasileiradeNormasTécnicas 1988 ,wereadopted‐sincethisestablishesacriteriontoconsidertheeffectsofneighboringbuildings.InAnnexGofthecode,NB‐6123establishesthatindicateaspresentedbyexpression7mustbeapplied.Itisworthnotingthat,duetothecomplexityofdeter‐miningwindeffectsinobliquedirectionstothebuildingaxes,thecodepredictswindincidenceonlyindirectionsat0ºand90º.

*

*

1.0 1.3

3.0 1.0

sFV

ds

FVd

7

Where:• s: Distance between the confronting faces of neighboring buildings; • d*: The smaller side dimension of the building under study, or half the diagonal of the building under study. Whichever is smaller.

Figures5,6and7presentthevaluesloadsoftheloadcoefficientsforallthestudiedconfirmations.Itisob‐served that inall situations theneighboringbuilding interferes inalldue to theactionof thewind in themainbuilding,sometimesincreasingthemandatothertimesexertingaprotectiveeffectreducingthem.

Fromfigure5wecansee that theprotectiveeffectsaremoresignificantwhentheneighboringbuilding iscloserandpositionedfrontallytothestudybuildingasitcanbeseeninthedirectionofwindincidentof90o,figure5 b and c .However, itcanbeobservedthatwhentheneighborwith thesamedistance ispositionedto theleeward,inthewakeofthemainbuildingthetendencyofprotectionisinvertedandthereisasignificantincreaseofthepreviouslyreducedefforts.Evenatthewindwarditispossibletoobservethattheneighborhastheeffectofelevatingthe forcesascanbeobserved inthe incidencesof60oand120o, figure5 b and c for theneighborpositionedinthelimitofthecontourD3andD4.Inthecaseoftorsion,itwasfoundthat,theproximitybetweentheneighborspromotedtheincreaseofthistwistascanbeobservedinfigure5 e forthe75o,105oand120odirec‐tions.

FortheV2alignmentsituation,itisobservedthat,asforthealignmentV1,theneighboringbuildingpromotessituationsofprotectiveeffect that ismoreefficientwhen it is to thewindward, in a frontaldirectionandwithsmallerdeviationsascanbeseeninthefigure6 a and d forthedirectionsintherangeof30°to60°.Itisobservedthat,exceptforthementioneddirections,agreatpartoftheresults,withtheneighborpositionedtothewindward,ortotheleeward,theresultsarepresentedlargerthanthevaluesconsideringtheisolatedmainbuildingdemon‐stratingtheinfluenceoftheneighboringbuildingonthemainloading.

ForV3alignmenttheprotectioneffectisobservedatlargerintervalsasshowninFigure7 b and c betweenthe15°and75°directions.Itisalsoobservedthatfordirectionsimmediatelyafterwardsthereisasignificantin‐creaseoftheloadsmodallydualtheVenturieffectcausedbythetwobuildingsraisingthewindvelocityandgen‐eratingtheincreaseofthepressuresinthemainbuilding.Inthecaseoftorsionthereisareversalofdirectioninrelationtowhatoccurswiththebuildingconsideredseparately,focusingontherangeofdirectionsbetween30°and75°.

Tables1,2and3presentananalysisoftheresultscollectedinthetestsforthedeterminationoftheforcecoefficientsfortheXandYdirections.Theamountofdatacollectedisprovidedforeacheffort,thenumberofresultsdiscarded,thenumberofresultsthatwerewithinthelimitsofVicinityFactorestablishedbytheBrazilianwindcode,thenumberofresultsthatwereabovetheselimits,andtheintensityofvicinityfactorsthatwereabovethecodelimits.Thesesamecriteriawereusedintheelaborationoftables4to6forthemomentsinthebasearoundtheaxesXandY,andforthetables7to9forthecalculationofthetorsion.ThediscardedresultsareresultsofvaluesofVicinityFactorsthatwereveryhighvaluesinsomespecificdirections,however,withoutinfactmakinga



greateffortinsuchdirections.Becauseitisaratiobetweentwovalues,whathappenedinthesesituationswasadivisionbyanumberveryclosetozero,whichcouldleadtoamisleadinganalysisoftheotherresults.

Tables1to5showthatmostoftheresultsconsideredvalidareabovethelimitsestablishedinthecode,reach‐ing84.7%,82.4%and78.3%foralignmentsV1,V2andV3respectively.Alsoalargedistributioncanbeseenfromtheseresultsalongthefour‐laneintensitiesproposedforallstudiedspacings.

Figure5:LoadcoefficientsforthealignmentV1: a ResultantforceinthedirectionoftheXaxis; B ResultantforceinthedirectionoftheYaxis; C BasemomentaroundaxisX; D MomentatthebaseabouttheYaxis; E Aroundthe

CAARCverticalcentralaxis.



Table1:ResultsofvicinityfactorsfortheresultingforceintheXandYdirectionsforthealignmentV1

Vicinity Results Dis‐

cardedre‐sults

FVwithinthelimitsofthe

code

FVabovethecodelim‐

its

FVintensityabovecodelimits

FV 1.2 1.2 FV 1.4 1.4 FV 1.6 FV 1.6

FV‐FX‐V1D1

24

1 1 22 0 8 7 7

FV‐FY‐V1D1 1 9 14 1 4 5 4

FV‐FX‐V1D2 1 1 22 1 6 10 5

FV‐FY‐V1D2 3 3 18 5 9 3 1

FV‐FX‐V1D3 1 1 22 0 10 8 4

FV‐FY‐V1D3 1 4 19 0 13 3 3

FV‐FX‐V1D4 1 3 20 0 6 11 3

FV‐FY‐V1D4 2 3 19 2 14 2 1



cardedre‐sults

FVwithinthelimitsofthe

code


its


FV 1.2 1.2 FV 1.4 1.4 FV 1.6 FV 1.6

FV‐FX‐V2D1

24

1 5 18 2 9 4 3

FV‐FY‐V2D1 1 4 19 2 7 7 3

FV‐FX‐V2D2 1 5 18 3 9 4 2

FV‐FY‐V2D2 1 4 19 0 8 9 2

FV‐FX‐V2D3 1 4 19 3 10 4 2

FV‐FY‐V2D3 1 3 20 1 10 8 1

FV‐FX‐V2D4 1 5 18 1 11 4 2

FV‐FY‐V2D4 2 3 19 1 7 9 2



cardedresults

FVwithinthelimitsofthecode


its


FV 1.2 1.2 FV 1.4 1.4 FV 1.6 FV 1.6

FV‐FX‐V3D1

24

0 5 19 4 8 3 4

FV‐FY‐V3D1 1 6 17 2 6 4 5

FV‐FX‐V3D2 1 4 19 3 7 6 3

FV‐FY‐V3D2 1 6 17 0 10 4 3

FV‐FX‐V3D3 1 5 18 2 9 5 2

FV‐FY‐V3D3 1 4 19 2 9 5 3

FV‐FX‐V3D4 1 4 19 4 9 4 2

FV‐FY‐V3D4 1 5 18 0 9 6 3

Tables4to6presenttheresultsinrelationtothemomentsaroundtheaxesofthebase.Alsoforthiseffortit

isclearthatthegreatmajorityoftheresultscollectedareabovethelimitsproposedbytheBraziliancode.Inthiscase,88.1%,84.5%and80.4%oftheresultsfoundforalignmentsV1,V2andV3respectivelywereabovetheselimits.Evenwith thevariationofdistancebetween themainbuildingand theneighboringbuilding, theresultsfound in this alignment,whichexceeded the codeative limit, alsopresent themselves inawelldistributedwayamongtheintensityrangesproposedinthisstudy.



Table4:ResultsofvicinityfactorsformomentuminthebasearoundtheXandYdirectionsforthealignmentV1


cardedresults

FVwithinthelim‐itsofthecode

FVabovethecodelimits


FV 1.2 1.2 FV 1.4 1.4 FV 1.6 FV 1.6

FV‐MX‐V1D1

24

2 8 14 1 4 5 4

FV‐MY‐V1D1 1 1 22 0 9 6 7

FV‐MX‐V1D2 2 4 18 7 7 3 1

FV‐MY‐V1D2 1 1 22 1 7 9 5

FV‐MX‐V1D3 2 3 19 3 11 3 2

FV‐MY‐V1D3 1 1 22 1 12 6 3

FV‐MX‐V1D4 1 3 20 2 14 3 1

FV‐MY‐V1D4 1 3 20 0 8 9 3



cardedresults




FV 1.2 1.2 FV 1.4 1.4 FV 1.6 FV 1.6

FV‐MX‐V2D1

24

1 3 20 2 6 8 4

FV‐MY‐V2D1 2 5 17 1 11 3 2

FV‐MX‐V2D2 2 2 20 0 8 9 3

FV‐MY‐V2D2 2 4 18 3 10 3 2

FV‐MX‐V2D3 1 3 20 1 10 8 1

FV‐MY‐V2D3 1 4 19 2 12 3 2

FV‐MX‐V2D4 1 2 21 2 7 9 3

FV‐MY‐V2D4 1 5 18 2 10 4 2



cardedresults




FV 1.2 1.2 FV 1.4 1.4 FV 1.6 FV 1.6

FV‐MX‐V3D1

24

1 6 17 2 7 2 6

FV‐MY‐V3D1 0 5 19 3 9 5 2

FV‐MX‐V3D2 2 5 17 0 10 4 3

FV‐MY‐V3D2 1 3 20 4 9 5 2

FV‐MX‐V3D3 1 4 19 2 9 6 2

FV‐MY‐V3D3 1 5 18 2 11 3 2

FV‐MX‐V3D4 1 5 18 0 10 5 3

FV‐MY‐V3D4 1 3 20 5 10 3 2

Tables7to9presenttheresultsfoundforthetorsionalmomentaroundtheaxisofthemainbuilding.Itcanbe

observedthattheamountofdiscardedresultsissignificantlyhigherthaninthecaseofotherefforts.Thisisduetothebehaviorofthebuildinginrelationtothiseffortinwhichtherearemanyinversionsofthetorsiondirectionwiththevariationofthedirectionofwindincidence,ascanbeobservedinFigures5 e ,6 e and7 e .Alsoforthiseffort,mostoftheresultswereabovethecodeativelimits,reaching63.0%,47.8%and54.7%foralignmentsV1,V2andV3respectively.Inthecaseoftorsion,agreaterdistributionofresultswithaVicinityFactorintensityisobservedabove1.6,especiallywhentheneighborispositionedfrontallytothemainbuilding.



Table7:ResultsoftorsionaroundtheCAARCforV1alignment


cardedresults



its


FV 1.2 1.2 FV 1.4 1.4 FV 1.6 FV 1.6

FV‐CT‐V1D1

24

6 7 11 0 4 3 4

FV‐CT‐V1D2 5 3 16 3 6 2 5

FV‐CT‐V1D3 2 2 20 3 5 4 8

FV‐CT‐V1D4 2 3 19 3 8 4 4

Table8:ResultsofthetorsionaroundtheCAARCforthealignmentV2


cardedresults



its


FV 1.2 1.2 FV 1.4 1.4 FV 1.6 FV 1.6

FV‐CT‐V2D1

24

7 9 8 2 4 2 0

FV‐CT‐V2D2 7 10 7 1 5 1 0

FV‐CT‐V2D3 6 8 10 5 3 2 0

FV‐CT‐V2D4 4 7 13 4 6 3 0

Table9:ResultsoftorsionaroundCAARCforV3alignment


cardedresults



its


FV 1.2 1.2 FV 1.4 1.4 FV 1.6 FV 1.6

FV‐CT‐V3D1

24

8 9 7 2 3 0 2

FV‐CT‐V3D2 10 7 7 2 3 2 0

FV‐CT‐V3D3 5 7 12 4 5 3 0

FV‐CT‐V3D4 4 7 13 4 5 4 0

Tables10to13presentthedataoftheeffortsforvicinityproposalsV1,V2andV3positionedattheboundary

ofthecontoursofD1toD4respectively.Sumsofallresultsobtainedinallassaysaregiven.ThelimitsofNBR‐6123havebeentakenasreference,wherecontourswithspacingsbetween0.17Hand1.0Hareconsidered,whereHrepresentstheheightofthebuilding.Thenumberofresultsthatwerewithinthelimitsproposedbythecodewerehighlighted,aswellasthevaluesthatexceededtheselimits,includingindicatingthepercentageoftheseinrelationtotheresultsconsideredvalid.Asinthetablespresentedabove,theresultsofVFthatexceededthecodelimitsaredividedintofourintervalswhere,inadditiontotheamountofresultsineachinterval,therespectivepercentageoftheseresultsispresentedinrelationtothetotalofreadingsoutofcode,besidestheaccumulatedpercentageofresultscomparedwiththetotalofreadingsconsidered,inordertoverifyfromwhichindextheresultswouldbecontemplatedbytheconfidenceinterval CI .

Manyresearchersperformedworkwithinthisrangeproposedbycode.MorethanhalfofthevicinitypositionsproposedbyThepmongkornetal 2002 wereinthisrange.Forasinglewinddirection,similartothe90ºdirectionofthisstudy,theyfoundinterferenceindexesofupto2.6forthemomentaroundtheXaxis,indexof3.4forthemomentaroundtheYaxisandindexof1.9fortorsion.TangandKwok 2004 usedsettingsverysimilartothoseofThepmongkornandintheirevaluationsforawinddirectionequivalentto90º,verifiedthatthepresenceofaneighboringbuildingproduceddisplacementswithinterferenceindexofupto1.6inthesamewinddirection,1.8inthecaseoftransversedisplacements,andindeterminingthetorsionangletheyfoundtheindexof1.9.Oliveira2009 workedwithspacingsbetween0.25Hto0.6H.Studyingthedynamiceffectsofthewindactingfrontallytothebuilding,equivalenttothedirection90ºofthepresentstudy,whereitfoundindicesofincrementofthetrans‐versal,longitudinalandtorsioninthebuildingsuperiorto2.0,andinsomecasesthisindexreachedmuchhigher



levels.Fontoura 2014 workedwithspacingsof0.25Hand0.63H,includingthepresenceofotherbuildingswithdifferentheightsanddifferentpositions.Theeffortsstudiedbyitreachedelevationratesof1.6fortheresultingforce,2.0forbaseflexionand2.2forthetorsionmoment.

Asintheworkoftheseresearchers,itcanbeverifiedforallsituationswiththeneighboringbuildingsposi‐tionedattheborderoftheD1contour,bothinsituationswheretheyweretothewindward,andinthesituationsinwhichtheywerepositionedtotheleeward,thatagreatpartoftheresultsexceededthelimitsproposedbytheBraziliancodesinrelationtoalltheeffortsanalyzed.Onthestudiedefforts,theleastthatcontainresultsoutsidethecodelimitsisthetorsionwith51.0%isshownintable10.Allothereffortshadatleast72.0%oftheresultsabovethelimitsindicatedbythecode.Usingaconfidenceintervalinwhichatleast95%ofthepopulationoftheresultsshouldbecontemplated,inthecaseofneighborswithboundarydistanceD1,alleffortswouldrequireaVFwithanindexabove1.6,asobservedinpreviousmentionedresearchers’studies.

Studieswithneighboringbuildingspositionedatdistancesabove1.0Haremoreunusual.Thepmongkornetal2002 intheirstudy,alsoconsideredthepresenceofneighboringbuildingsforspacingsbetween1.0Hand1.5H.Inthesecases,theyfoundvicinityinterferenceindexesofupto1.7forthemomentaroundtheXaxis,from2.3formomentumaroundtheYaxisand1.5fortorsion,valueslowerthanthesituationswiththenearestvicinity,butstillabovethelimitsproposedbytheBrazilianCode.TangandKwok 2004 reachedindexesoftheorderof1.7forthedisplacementtowardsthewind,1.4fortransversedisplacementsand1.8forthetorsionangleoftheirstudy,valuesclosetothosefoundfornearestpositionedneighbors.

InsituationswheretheneighborswerepositionedattheboundaryoftheD2contour,thetwistingwasalsotheeffortthatleastpresentedresultsoutsidethecodelimitswith45.2%ofthevalidvalues,aspresentedintable11.Fortheothereffortscalculatedforthiscontouranevenmorecriticalsituationisobservedwhereatleast78.0%oftheresultswereabovethecodelimits.Usingthesameconfidenceintervalprincipleforthiscase,torsionwouldbetheonlyeffortmetwiththeuseofaVFwithanindexof1.6.ThisindexisveryclosetotheindexesfoundbyThepmongkornetal 2002 andTangandKwok 2004 intheirresearches.

Thepmongkornetal 2002 proposedfewsituationswheretheneighborwasintherangebetween1.5Hto2.0Hofdisplacement.Inthesecases,theyfoundvicinityinterferenceratesofupto1.4forthemomentaroundtheXaxis,1.5formomentumaroundtheYaxisand1.3fortorsion.Forthisregion,TangandKwok 2004 foundinter‐ferenceindexesoftheorderof1.4fordisplacementsinthewinddirection,1.5inthetransversedirectionand1.6inthetorsionangle.Itisobservedaproximitybetweentheinterferenceratesinbothresearches.

ForthesituationinwhichtheneighborswerepositionedattheboundaryoftheD3contour,thetorsioncon‐tinuesbeingtheeffort,amongthosestudies,oneofthatpresentslessresultsoutsidethecodelimits.Evenso,asignificantincreaseintheamountofresultsabovetheselimitscouldbeobservedforalleffortswherethetorsionpresented71.2%oftheaboveresultsandtheothereffortswereallabove84.0%accordingtothedatapresentedinTable12.Alsointhiscase,theVF,tomeettheconfidenceinterval,shouldbegreaterthan1.6.

Finally,thevicinityproposalspositionedattheboundaryoftheD4contour,eventhoughtheywerefurtherapart,presentedalargeamountofresultsoutsidethecodelimitswherethetorsionhadmorethan72.6%oftheresultsabovetheselimitsandtheothereffortsabove82.0%,ascanbeobservedintable13.Asintheothercontours,inthiscase,theVFwouldalsoneedtobegreaterthan1.6.

Table10:ResultforcontourD1

Loads

Re‐sults

Discardedre‐sults

FVwithinthelimitsofcode


its

IntensityofFVoutofcode

FV 1.2 1.2 FV 1.4 1.4 FV 1.6 FV 1.6

Results

%

Results

%

Acumu‐latedre‐sults%

Results

%


Results

%


Results

%

FX‐D1

72

2 11 59 84.3 6 10.2 24.3 25 42.4 60.0 14 23.7 80.0 14 23.7

FY‐D1 3 19 50 72.5 5 10.0 34.8 17 34.0 59.4 16 32.0 82.6 12 24.0

T‐D1 21 25 26 51.0 4 15.4 56.9 11 42.3 78.4 5 19.2 88.2 6 23.1

MX‐D1 4 17 51 75.0 5 9.8 32.4 17 33.3 57.4 15 29.4 79.4 14 27.5

MY‐D1 3 11 58 84.1 4 6.9 21.7 29 50.0 63.8 14 24.1 84.1 11 19.0




Loads

Re‐sults

Discardedre‐sults



its


FV 1.2 1.2 FV 1.4 1.4 FV 1.6 FV 1.6

Results

%

Results

%


Results

%


Results

%


Results

%

FX‐D2

72

2 9 37 80.4 6 16.2 32.6 16 43.2 67.4 10 27.0 89.1 5 13.5

FY‐D2 2 10 36 78.3 0 0.0 21.7 18 50.0 60.9 13 36.1 89.1 5 13.9

T‐D2 17 17 14 45.2 3 21.4 64.5 8 57.1 90.3 3 21.4 100.0 0 0.0

MX‐D2 4 7 37 84.1 0 0.0 15.9 18 48.6 56.8 13 35.1 86.4 6 16.2

MY‐D2 3 7 38 84.4 7 18.4 31.1 19 50.0 73.3 8 21.1 91.1 4 10.5


Loads

Re‐sults

Discardedre‐sults



its


FV 1.2 1.2 FV 1.4 1.4 FV 1.6 FV 1.6

Results

%

Results

%


Results

%


Results

%


Results

%

FX‐D3

72

3 10 59 85.5 5 8.5 21.7 29 49.2 63.8 17 28.8 88.4 8 13.6

FY‐D3 3 11 58 84.1 3 5.2 20.3 32 55.2 66.7 16 27.6 89.9 7 12.1

T‐D3 13 17 42 71.2 12 28.6 49.2 13 31.0 71.2 9 21.4 86.4 8 19.0

MX‐D3 4 10 58 85.3 6 10.3 23.5 30 51.7 67.6 17 29.3 92.6 5 8.6

MY‐D3 3 10 59 85.5 5 8.5 21.7 35 59.3 72.5 12 20.3 89.9 7 11.9


Loads

Re‐sults

Discardedre‐sults



its


FV 1.2 1.2 FV 1.4 1.4 FV 1.6 FV 1.6

Results

%

Results

%


Results

%


Results

%


Results

%

FX‐D4

72

3 12 57 82.6 5 8.8 24.6 26 45.6 62.3 19 33.3 89.9 7 12.3

FY‐D4 5 11 56 83.6 3 5.4 20.9 30 53.6 65.7 17 30.4 91.0 6 10.7

T‐D4 10 17 45 72.6 11 24.4 45.2 19 42.2 75.8 11 24.4 93.5 4 8.9

MX‐D4 3 10 59 85.5 4 6.8 20.3 31 52.5 65.2 17 28.8 89.9 7 11.9

MY‐D4 3 11 58 84.1 7 12.1 26.1 28 48.3 66.7 16 27.6 89.9 7 12.1



4CONCLUSIONS

Thepurposeofthevicinityfactoristotakeinaccountthewindeffectscausedinacertainbuildingduethepresenceofotherbuildingsintheproximityofthisone.Ingeneral,thecriterionforpredictingtheuseofthisfactoristhedistancebetweenbuildings.

Thefinalconsiderationsmadefromtheanalysisoftheresultspresentedpreviouslyconsideredthepositionoftheneighboringbuildingaswellasitsdistancetotheinstrumentedbuilding.

Inallthesituationsanalyzedinthisstudyitwasdemonstratedthatthepresenceofabuildingaltersthewindloadsinabuildingnexttothisone.Itisevidentthatthechangesofmajorinterestforthestructuralanalyzesarethosethatpromotetheincreaseoftheloadvaluestobeconsidered.Forthisitisofgreatimportancetoknowifsuchincreaseoccur,whatwouldbethesituationsinwhichtheyoccurandwhattheintensityoftheincreases.

Withtheresultsfound,itcouldbeconcludedthatiftheneighborispositionedinthewindwardorleewardofthebuilding,thiswillgenerallypromoteanincreaseintheloadswhichwillbedeterminedbythewinddirection.

Evenconsideringfourdifferentboundarylimitsinthisstudy,forthedeterminationoftheVicinityFactor,onlyinsomecasesthestatisticalcriterionofconfidenceinterval,inwhichatleast95%oftheresultsaretobeconsid‐ered,wasmet.

Anotherpointthatcouldbeobservedisthattheintensityofeffortrequiredtocontemplatetheelevationsofeffortsoccurredinthesituationsproposedinthisstudywouldbeatleast60%ofthevaluesofeffortsfoundforabuildingconsideredasactingalone,situationadoptedbyNBR6123.

Finally,itiscleartheneedtofurtherresearchinordertoclarifytheprotectioneffectspromotedbythepres‐enceofavicinitybuildingand,mainly,thequestionofthenecessityofthemajoringefforts.Consideringthepres‐enceofmorethanonebuildingaswellastheeffectsofsoil‐structureandfluid‐structureinteractionsareparame‐tersthatcancontributesignificantlyinthisfieldofresearch.

5ACKNOWLEDGMENTS

TheauthorsaregratefulforthefinancialsupportofCNPq Brazil ,whichmadethisresearchpossible.AlsothankedisthestaffoftheLaboratóriodeAerodinâmicadasConstruçõesoftheUniversidadeFederaldoRioGrandedoSul,PortoAlegre,Brazil,fortheavailabilityanddedicationincarryingoutthetestsofthiswork.

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experimental study of the neighborhood effects on the mean

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