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ThisreportiscopyrighttoRHIwrittenanduploadwithsomemodificationtohidetheclientnameforeducationalproposeforanycommentspleaseemailkhaled_eid@yahoo.com
ReviewReport
ClientCementCompanyUnburnedclinkersteelsilo
11/18/2011
11/18/2011 Eng.AmedSaeedCivilEng.Khaled
Eid,Msc,PE
Civil
0Date Writtenby Reviewedby Approvedby Version
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Contents1 Introduction.......................................................................................................................................... 3
2 Unburnedclinkersilo............................................................................................................................ 3
2.1 Receiveddocumentsanddrawings.............................................................................................. 4
2.2
Reviewmethodology
....................................................................................................................
5
3 Analysisinputdata................................................................................................................................ 5
3.1 FiniteElementProgram................................................................................................................ 5
3.2 Temperatureeffect....................................................................................................................... 6
3.3 Windload...................................................................................................................................... 6
4 Design.................................................................................................................................................... 6
4.1.1 Silowall................................................................................................................................. 6
4.1.2 Silobottomhopper............................................................................................................... 7
4.1.3 Siloroof................................................................................................................................. 7
4.1.4 Silosupportingconcretestructure....................................................................................... 7
5 Fabricationanderection....................................................................................................................... 8
6 Summaryandconclusion...................................................................................................................... 9
7 Recommendation.................................................................................................................................. 9
References.................................................................................................................................................. 10
Appendix1................................................................................................................................................. 11
Appendix2
.................................................................................................................................................
12
Appendix3................................................................................................................................................. 13
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1IntroductionClientCement(CLIENT)plant islocatedinClient,Elkarak
Jordon90KmsouthAmman.Thedryprocessplanthasa
productionof5000tonperdaystartedcommissioningin
September2010.
MechanicallydesignedbyXXX,Germanyreferred
inthisreportasthemechanicaldesigner.
Managedbythe consultantHOLTEC,India
referredinthisreportastheconsultant.
CivildesignengineerTEM,Turkeyreferredinthis
reportasthedesignerorcivildesigner.
ThecontractoristheMIDCONTRACTING,
AMMANreferredinthisreportasthe
contractor.
At the requestofClientcement fromRHI to review the
structural design and construction integrity for the
unburnedclinkersilo
RHIvisitedthesiteon29thofNovember2011andtalked
to concerned parties then inspected the silo, it was
noticedthesiloisemptyandmaterialisaccumulatedon
the concrete platform below as a sign of emergency
discharge.Stairaccesswascoveredwithmaterialinsuch
it is during initial filling operation the silo bottom deformed as shown and there are is sign of
deformationatthesupportingringbeamalsothereisacrushinginthebearingareaatthesilosupport
Refertoappendix1forphotos.
2 UnburnedclinkersiloTheunderburnetsiloisdesignedtostoretherejectedclinkersoitmayberecycled bysomeratiointhe
processagain.Usuallystoredinsiloseithersteelorconcrete.Inourcaseitisasteelsilowithadesigned
capacityof1500tonbasedonclinkerdensityof1.3ton/m3,thesilodiameteris10meterandheightof
16.0meterwithaflat bottomhopperbottomdiameterof7.5meterandheightof3.75meter.Thesilo
issupportedatlevel15.2onfourconcretebeamssupportedinfour concretecolumns.
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2.1 ReceiveddocumentsanddrawingsThesedrawingweresubmittedbyClientCementCompanyasthelatestgeneralarrangementdrawings.
FabricationdetailsofunderburnerXXX 84189756BAsheet1
FabricationdetailsofunderburnerXXX 84189756BAsheet2
Clinkertransportandstoragegernalarrangement 84127249UA
KCP15C001_05.dwg (15UNBURNTCLINKERHOPPER) FOUNDATIONPLAN
KCP15
C002_01.dwg
(15
UNBURNT
CLINKER
HOPPER)
+2.500
LEVEL
FORMWORK
PLAN
KCP15C003_01.dwg (15UNBURNTCLINKERHOPPER) +5.900LEVELFORMWORKPLAN
KCP15C004_02.dwg (15UNBURNTCLINKERHOPPER) +8.400LEVELFORMWORKPLAN
KCP15C005_00.dwg (15UNBURNTCLINKERHOPPER) +15.200LEVELFORMWORKPLAN
KCP15C006_01.dwg (15UNBURNTCLINKERHOPPER) COLUMNAPPLICATIONPLAN C1C2C3
KCP15C007_00.dwg (15UNBURNTCLINKERHOPPER) +2.500LEVELSLABREINFORCEMENT
PLAN
KCP15C008_01.dwg (15UNBURNTCLINKERHOPPER) +5.900LEVELSLABREINFORCEMENT
PLAN
KCP15C009_02.dwg (15UNBURNTCLINKERHOPPER) +8.400LEVELSLABREINFORCEMENT
PLAN
KCP15C010_00.dwg (15UNBURNTCLINKERHOPPER) +15.200LEVELSLABREINFORCEMENT
PLAN
KCP15C011_00.dwg (15UNBURNTCLINKERHOPPER) REBARDETAILSOFFOUNDATIONS
KCP15C011_01.dwg (15UNBURNTCLINKERHOPPER) REBARDETAILSOFFOUNDATIONS
KCP15C012_00.dwg (15UNBURNTCLINKERHOPPER) BEAMDETAILS B001B002B003B004
B005B006B101B102B103B104
B105B106B107B108B109B110B204
KCP15C013_03.dwg (15UNBURNTCLINKERHOPPER) BEAMDETAILS B111B201B202B203
B205B206B207B208B209B210
B211B212B213B214B215B216B301
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KCP15C014_02.dwg (15UNBURNTCLINKERHOPPER) STAIRPLANANDDETAILS
2.2 ReviewmethodologyDespiteof RHIrequestedseveraltimesfromCLIENTtoprovide
theoriginaldesigncalculationbutwedidnotgetanythingtill
nowwhichraiseaquestionifthisstructurewasalready
designedbyXXXornot?Andhowitwasapprovedifthereisno
supportingdesign
document?
Thusreviewmethodologywasappliedbymakingan
independentsetofcheckanalysisandcalculations,accordingto
materialandplatethicknessprovidedinthedrawings.
Thefollowingarethecodesandstandardsusedinreview
BSEN19914:2006ActionsonstructuresSilosand
tanks.
LoadscombinationstotheASCE705 minimumdesign
loadsof
structure
Wind,snowandthermalloadsareaccordingtothe
Jordanianloadingcode.
DesignofsteelmembersaspertheAmericancode
AISCASD.
MechanicalloadsappliedexactlyasprovidedbyXXX
onlywindloadsarecalculated.
3 Analysisinputdata3.1 FiniteElementProgramThereisnoprogramyettopredictthematerialflowsointhisstudythesilobucklingbehaviorwas
investigatedwithlinearbucklinganalysisofSAP2000(Nonlinearv.14).SAP2000isageneralpurpose
structuralfiniteelementanalysisprogram.Allcircumferentialandlongitudinalstiffenersweremodeled
asframeelements.
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3.2 TemperatureeffectTheouterwallsofthesilocanexpandduringdayandcontractatnightasthetemperaturedrops,if
thereisnodischargetakingplaceandmaterialinsidethesiloisfreeflowing,itwillsettleasthesilo
expandsbecauseitcannotpushedbackupwhenthesilowallcontract.
Atemperaturedifferenceof100degreeisconsideredduetotheaverageeffectofhotclinkerwhen
enteringthesilo.
3.3 WindloadCircularbins,ontheotherhand,areverysensitivetowindloadingbecauseofthevarying
pressure/suctiondistributionofthewindloadingaroundthecircumference,andthelackofstiffnessof
theshell
in
resisting
this
loading.
The
required
thickness
of
plate
in
the
upper
strakes
of
acircular
bin
is
oftendeterminedbythewindloading.
Windbucklingischaracterizedbythe
formationofoneormorebuckleson
thewindwardfaceoftheshell.Wind
alsoproducesanoverturning
momentonatallbin,whichinducesa
verticalcompressivestressinthe
leewardface;thisreacheda
maximumatthebaseofthebin,
wheretheshellneedstobechecked
againstbuckling
4 DesignAsstatedbeforenoinformation
abouthowthissiloisdesignedto
whichcode,didanychangedineither
heightorbottomduringerection?no
historicalinformationavailable.
Sothisreportwillnotbeabletojudgethedesigncalculationbutwillonlyrefertotheasbuiltonsite
andXXX
drawing
841
89
756BA
rev
2.
4.1.1 Si lowallSilomaterialdoesnotactlikeafluid;drymaterialshavefrictionalorcohesiveresistanceandtendto
formdomeswiththesilowallthatpreventsitfromfallingfreelydownward.
Thelateralpressureonthesiloshellfromthedrymaterialsisofdifferentcharacterthanthelateral
pressureontheretainingwallfromsoilatthebackofthewall.
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Thedesignerappliesaconstant10mmthicknessfor
thewallandthebottomhopper;practicallyitistoo
smallwhenconsideringallowanceforrustand
aberrationforsuchlargesizesilos.Thecritical
bucklingstressinthewallisgoverningthethickness
requiredtocarrytheverticalcompressionload.
Itwasfoundbyanalysisthatthesilowallisonlysafe
atthetopthirdofthesilobutinallotherlocationis
unsafestressandbuckling.
4.1.2 Si lobottom hopperThebottomhopperisdesignedas 10mmwithadiameterof7.5meterstiffenedbyangle75x10,itis
foundtobeawayunsafeaswell.Refertoappendix3fordetails.4.1.3 Si loroofThetoproofwithplate10mmisfoundtobesufficienttosupporttheappliedliveloadsbutthe
supportingsteel beamsareunsafe(thebeamspansforsevenmetersandsupportingawidthofoneand
halfmeterandassignedasUPN200).
4.1.4 Si losupport ingconcrete st ructure
Thesiloissupportedinfourbearingpointsona
200cmx90cmconcretebeamsbyvisualinspection
thesebeamssufferingfromdiagonalcracksand
concretecrushing atoneofthebearingpoints,
furthermoreconcretebeamsatlevel8.4suffering
verticalcracksinbothsides.
Itisalsovisuallynoticedinsomelocationsome
concretehoneycombscreatingavoidsinthe
concretebeams
and
left
without
curing
that
is
also
raiseaquestionabouttheconcretequality.
RHIrequestedtheconcretestructuredrawingsandrunandindependedcheckingfor the whole
structure.
IT wasfoundthatthesupportingbeamstobeunsafeinshearwithevidenceoftheshearcrack,while
forlevel8.4allbeamsaresafeaccordingtothedesignsothecracksmaybeasareasonofthefalling
materialontheapronfeederwhenthesilobottomdeforms.
Refertoappendix2forsupportingstructurechecking.
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5 FabricationanderectionAlthoughappropriatesizesasperthedesigndrawingareusedbutmanyfabricationanderectionerrors
arespottedduringinspectiongivingabadimpressionaboutthequalitycontrol.
1. Thebottomstiffenersaretackweldedandnotinfullcontactwiththesilobody.
2. Thestiffenersarenotcontinueswithagapatmidspanwhereabeigestload.
3. Thebottomstiffenersarenotconnectedtotheverticalonesthustheyarenottransferringthe
loadtothesupports.
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6 Summaryandconclusion
Ourstudyconcludesthatthe
steelsiloisunderdesigned
sufferingmanydesignissues
Theseissuesaresummarized
asfollows
Thesupporting
concretebeamisjust
safeinbendingbut
unsafeinshearby18%thisexplainsthe45degreescracks.
Duetothebottomexcessivedeformationitdamagedtheapronfeederwithamaterialfalls
addingunexpectedloadedontheconcretebeamsatlevel8.4creatingcracksinthesebeams.
Thepartymostresponsibleforthebottomcollapsewasthedesignerbecauseallitemsare
unsafethewalls,theflatbottom,thestiffening,theringbeamandtheroof,notasingleitemin
thissiloisfoundtobesafe.
The
erector
and
fabricator
work
was
away
from
standard
leading
to
decrease
more
the
capacity
howeverthiswillnotaloneleadtothecollapse
Thereisnosignforanyexcessiveusage,lackofmaintenanceoroperationalmisuse.
7 RecommendationWeproposethefollowingactionsaspartoftherectification
Wetriedmanyrepairalternativebutnoneofthemsolveallissuessowerecommend
replacingthesiloasthebestoption.
Itisadvisabletosupportthesilooneightpointstodistributetheconcentratedloadby
addingsteel
beams
at
45degree.
Thesupportingbeamswillneedtobestrengthenedagainstshear.
Crackedbeamsinlevel8.4shouldbestrengthened.
Concretebuildingshouldbeinspectedforanyconstructiondeficienciesandrepairedbefore
fillingthesilo.
Concretecoretestmayberequiredtoevaluatetheconstructedconcretequalityandif
possibletochecktheexistingsteelbarsandstirrupsatrandomlocation.
No access to the silo support to allow for inspection at bearings it is recommended to addladder from level 8.4 to 15.2
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References
1. AmericanWeldingSociety(AWS),550NW42dAvenue,Miami,FL22126.
2. RubinM.Zallen,P.E.,Collapseofsteelsilo3. AmericanIronandSteelInstitute(AISI),110117thSt.,NW,Suite1300,Washington,
4. BahaaMachaly.,Structuralsystemsforwindandearthquakeloads.5. TheJordanianloadingcodeArabic originalcopyAmman2006.6. ACIstandards31391,Standardpracticefordesingandconstructionofconcretesilosand
stackingforstoringgranularmaterials
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Appendix1Site
Photos
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Appendix2Concretebuildingreview
Notincludedinthiseducationalcopy
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Appendix3Analysisanddesignchecking forsilo
Notincludedinthiseducationcopy