Simula on models for implementa on of lean produc on ...
Transcript of Simula on models for implementa on of lean produc on ...
TRANSPORTES | ISSN: 2237-1346 130
Simula�on models for implementa�on of lean
produc�on concepts in earthmoving and paving Levy Sarmento de Matos1, Bruno de Athayde Prata2, Ernesto Ferreira Nobre Júnior3,
Francisco Heber Lacerda de Oliveira4
1Universidade Federal do Ceará, [email protected] 2Universidade Federal do Ceará, [email protected] 3Universidade Federal do Ceará, [email protected] 4Universidade Federal do Ceará, [email protected]
Recebido:
18 de junho de 2016
Aceito para publicação:
12 de janeiro de 2018
Publicado:
30 de abril de 2018
Editor de área:
Kamilla Vanconcelos
ABSTRACT
Studies show that, despite the resistance of professionals to new modes of produc�on,
the applica�on of Lean Construc�on philosophy improves the opera�ons produc�vity,
reducing costs and improving the quality of the final product. However, methodologies
which evaluate the impacts of the implementa�on of this philosophy to road construc-
�on opera�ons are scarce. This study aims to verify the improvements that the applica-
�on of the Lean Construc�on Philosophy can bring to earthwork and paving opera�ons
in a ma7er of execu�on �me and overall cost by developing a computa�onal model and
simula�ng different applica�on scenarios and checking their benefits through a compar-
ison of ac�vity dura�ons and equipment costs. A;er model development and data anal-
ysis, it was found that the models that incorporated the guidelines of the Lean philoso-
phy got faster (up to 30% reduc�on in run�me) and cheaper (reduc�on of up to 28% on
cost) results in terms of use of equipment’s.
RESUMO
Estudos mostram que, apesar da resistência de profissionais a novos modos de produ-
ção, a aplicação da filosofia Construção Enxuta melhora a produ�vidade das operações,
reduzindo custos e melhorando a qualidade do produto final. No entanto, metodologias
que avaliam os impactos da implementação desta filosofia para a construção de estra-
das são escassas. Este estudo tem como obje�vo verificar as melhorias que a aplicação
da Filosofia Construção Enxuta pode trazer para terraplenagem e operações de pavi-
mentação em matéria de tempo de execução e custo total pelo desenvolvimento de um
modelo computacional e simulação de diferentes cenários de aplicação e verificação de
seus beneGcios através de uma comparação de duração de a�vidades e custos de equi-
pamentos. Após o desenvolvimento do modelo e análise dos dados, descobriu-se que
os modelos que incorporavam as diretrizes da filosofia Enxuta ficaram mais rápidos (até
30% de redução na execução) e mais baratas (redução de até 28% nos custos), resulta-
dos em termos de uso de equipamentos.
Keywords:
Lean construc�on,
Decision support systems,
Earthmoving,
Paving.
Palavras-chaves:
Construção enxuta,
Sistema de suporte à decisão,
Terraplenagem,
Pavimentação.
DOI:10.14295/transportes.v26i1.1405
1. INTRODUCTION
Earthmovingandpavingservicesarerelatedtothemovementofthousandsoftonsofmaterials,
usingagreatamountofheavymachinesandrequiringaspecialattentionfromconstruction
companiesandcontractors.Therefore,therationalizationintheselectionofequipment,aswell
asthe�leetsizing,areactionsofgreatimportance,enablingthereductionoftherelatedcosts
andtimes.
Modelingasystemallowsabettercomprehensionoftherealprocess,enablingtheplanners
to forecast their behavior and to determine interventions for themitigation of failures and
losses.Theoperationofheavymachinesinearthmovingandpavingservicescanberepresented
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byDiscreteEventSystemsTheory,allowingsomecomputationalmodelinglikethesimulation,
forinstance.
TheLeanConstructionphilosophyisbasedonthestudyoftheprocesses,aimingthemitiga-
tionofthediscontinuitiesandremovingtheactivitieswhichdonotaddvaluetothe�inalprod-
uct. Insomesituations, themanagers canproposea rebuildingof theproductiveprocesses,
modifyingcompletely theoriginalprocess(Koskela,1992).Heavycivilconstruction,suchas
earthmovingandpavingservices,isaprominentareaforapplicationofleanconcepts.
Regardingthediscreteeventsimulationinearthmovingprojects,severalworkshavebeen
reportedintheliterature.SeveralsimulationapproachesarepresentedbyJayawardane&Price
(1994a,1994b),MarzoukandMoselhi(2000),Marzouk(2002),Alkassetal.(2003),Yangetal.
(2003),Bargstadt&Blickling(2005),Moselhi&Alshibani(2007),Prataetal.(2008),Zhang
(2008)andChengetal.(2011).Concerningtheapplicationofsimulationmodelsforimplement-
ingleanconcepts,somepapershavebeenreportedintheliterature:Tommelein(1998),Al-Su-
dairietal.(1999),Halpin&Kueckmann(2002),Farraretal.(2004),Hosseinietal.(2012)and
Hosseinietal.(2014).
Althoughtheliteratureonearthmovingsimulationisvast,thepropositionofmodelsforim-
plementation of lean concepts in earthmoving and paving is very limited. Farrar et al.
(2004)wastheonlystudyinthespecializedliteraturetoapproachtheimplementationofLean
Constructionphilosophyinearthmovingandpavingservices.Theseauthorsdonotconsider
theconstructioncosts,onlytheactivitiesdurations.Inaddition,suchauthorsconsideravaria-
bleproductivitythatismeasuredthroughthesimulations.
ThispaperaimsatpresentingdiscreteeventsimulationmodelsforimplementationofLean
Constructionconceptsinearthmovingandpavingservices,inanintegratedmodel.
Threesimulationmodelswereproposed:onewithoutleanconceptsandtwoapplyinglean
concepts.Themodelsconsiderthefollowingactivities:earthmoving,sub-base,baseandasphalt
surfacing. Theproposedmodels inthispaperconsider:(i)a�ixedproductivitythat istaken
fromaservicecostelaboration;(ii)constructioncosts;and(iii)constructionduration.Realdata
wasgathered,enablingthevalidationoftheproposedapproachesaswellasthecomparison
betweentherealsystemandthesuggestedoperationalpolicies.
2. PROBLEM DESCRIPTION
EarthmovingandpavingactivitiesconsistinapromisingareafortheapplicationofLeanPro-
ductionconceptsbecausetheseoperationsarerelatedwithmovementandhandlingoflarge
amountsofmaterials,usingagreatquantityofexpensiveresources(Mitoso,2007).Theappli-
cationoftheLeanPhilosophyinheavycivilconstructioncanavoidseveralproblemssuchas
lossesofmaterials,reworksandtheratesofequipmentinactivity.
Theproblemunderstudyconsistsinthedevelopmentofamethodologywhichallowsthe
testingoftheimplementationofLeanProductionpoliciesinearthmovingandpavingservices,
aimingthequanti�icationoftheimpactsofthesepractices.IntheFigure1,onecanobservethe
operationsconsideredinthemodelingprocess.
Theproposedmodelsarecomposedoffourblocksofactivities,consideredinasequential
manner:Earthmoving,Sub-base,BaseandAsphaltSurfacing.Forthedevelopmentofthedis-
creteeventsimulationmodelforearthworks,itwasusedthesoftwareSimul8(HaugeePaige
(2004),Chwifetal.(2015)),whichisawell-knownsimulatorinthecorporatebusiness.With
theSimul8,onecanobtainseveralperformanceindicatorsofthemodeledsystem,suchascycle
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times,equipmentutilizationrates,resourceutilizationratesandqueuesformation,amongoth-
ers.
Figure 1. General scheme of the modeled activities
3. METHODOLOGY
Inthiswork,threemodelsareproposed:onemodeledtherealityandtheothersconsiderlean
concepts. In the �irstmodel (namedModel 1), the lean concepts arenot considered. In this
model,doesnotoccurtheoverlappingoftheactivities,thatis,theoperationsareperformedin
asequentialmanner.Forexample,thesub-baseoperationsstartaftertheendoftheearthmov-
ingoperations,andsoon.
Inthesecondmodel(namedModel2),someoperationsareconsideredwithoverlapping,
facilitatingtheexecutionoftheactivitiesaswellasmaximizingtheutilizationoftheloadersand
reducingtheidlenessofthedumptrucks.
Inthethirdmodel,itwasproposedanewschedulingfortheexecutionofthebaselayer.In
theproposedschedule,thebaseoperationsareperformedconcomitantlywiththeearthmoving
and sub-base operations. Thus, it is needed a secondwork front, increasing the amount of
equipment,butreducingsubstantiallytheconstructionstotalduration.
3.1 Lean concepts adopted in the models
Aimingtoverifytheef�iciencyimprovementofearthmovingandpavingservices,incomparison
withthecurrentoperationofthesesystems,somestrategieswereimplementedintheproposed
models.TheLeanConstructionconceptsutilizedinthemodelingaredescribedasfollow:
a) Specifyvalue:valuecanbeviewedbythedifferencebetweenthebene�itsandcosts
ofagivenprocess.Thevalueoftheprocessesneedstobespeci�ied,aimingtheirfur-
theroptimization.
b) Mapthevaluestream:Thismappingconsists in thedeterminationofall thesteps
performedinthevaluestream,removing,wheneverfeasible,thosestepsthatdonot
addvalue.
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c) Makevalue�low:Thisconceptconsistsinthemakingthevalue-additionstepsarise
innarrowsequencesothegoodswill�lowsmoothlyintheprocess.
d) Pullvalue:Theactivitiesmustpullvaluefromthenextstepintheprocess.
IntheFigures2and3,theleanconceptsadoptedintheModels2and3,whicharebasedin
theconceptualframeworkofLeanProductionTheoryproposedbyAl-Sudairietal.(1999)are
illustrated.
Figure 2. Lean concepts considered in the Model 2
Figure 3. Lean concepts considered in the Model 3
3.2 Ac7vi7es considered in the models
Thedevelopedmodelshavefourdistinctandindependentblocksofactivities,whichcanbeop-
timizedinrelationtotheequipment�leetandthesimultaneityofoperations.The�irstblock
representstheearthmovingactivities,consideringcut,�ill,haulingandcompaction,intheana-
lyzedarea.Thesecondrepresentsthesub-baseoperations,inwhicharemodeledcut,�ill,haul-
ing,compactionandleveling.TheabovementionedprocessesareillustratedinFigure4.
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Figure 4. Simplified cycle for Earthmoving and Sub-base
In thethirdblockof themodel,arerepresentedthe inherentoperationsto thepavement
base.Intheproposedmodels,thebaseisasand-gravelmixcomposedof70%ofsoiland30%
ofgravel.Therefore,themodelconsidersthehaulageofmaterialsfromtheborrowpitstothe
soilmixers,inwhichisassumedthatathird-partycompanyhastransportedtherocks.Afterthe
crushingandmixingofthematerials, thestabilizedsoil istransportedtothecentroidofthe
consideredsection,wherethematerialisunloadedandcompacted.Thebaseprocessisillus-
tratedintheFigure5.
Figure 5. Simplified cycle for Base
Finally,thelastblockofthesimulationmodelconsistsintheapplicationofalayerofHotMix
Asphalt(HMA),withathicknessof5cm.Subsequentlyisperformedthespreading,�inishingand
compactingofthelayer.ItcanbeobservedthattheHMAproductionisadmittedasperformed
byathird-partycompany,beingthematerialreceivedonthetrack.Theasphaltsurfacingpro-
cessisillustratedintheFigure6.
Figure 6. Simplified cycle for asphalt surfacing
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3.3 Proposed simula7on models
Theabovementionedsubsystemsweremodeled in theSimul8, an importantdiscreteevent
simulatorintheengineeringsector.Simul8hasagraphicalinterfacethatenablestheuserto
constructmodelsinasimpleway.Theprocessesofdatainputanalysis,aswellasofsimulation
analysisarefacilitatedbytherobustinterfaceofSimul8.
Theearthmovingprocess is illustrated in theFigure7. In thismodel, thebackhoe -dump
truckcycle isrepresented likeadiscreteeventsystem,withthisdynamicnature.Firstly, the
backhoegetsmaterialinanembankmentandloadsthedumptruckwhileitscapacityisavaila-
ble.Afterthat,thedumptruckperformsthetransportationofthematerialstothe�ill,perform-
ing theunloadingoperation. Inaddition, theoperationsof levelingandcompactionareper-
formedfortheconclusionofearthmovingprocess.
Figure 7. Earthmoving model in Simul8
Thesub-baseprocessisillustratedintheFigure8.Ingeneralterms,thesub-baseprocessis
roughlyequaltotheearthmovingprocess.Thekeydistinctionbetweenthemisthatinthesub-
baseprocess,thematerialsmusthaverollingresistancecharacteristics,whichisnotthecase
withearthmovingprocess.
Figure 8. Sub-base model in Simul8
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ThebaseprocessisillustratedintheFigure9.Intheproposedmodelisconsideredthefol-
lowingcombinationofparameters:thebaseiscomposedby70percentgraveland30percent
soil.Thedumptrucktransportsthematerialfromdeposittothesoilmixer.Itisconsideredthat
theoutsourcedcompanyhasalreadydeliveredthestones.Afterstonecrushing,thesoilissta-
bilized,deposited,distributedandcompacted.
Figure 9. Base model in Simul8
Finally,thelaststageofthesimulationistheasphaltsurfacingmodel,asillustratedinthe
Figure10.Inthissubsystem,theactivitiesareperformedinalinearwayfortheapplicationof
HMA,withathicknessof5cm.Firstly,theHMAisproduced.Itisimportanttoobservethatin
presentmodel this production is consideredoutsourced and thematerial is received in the
track.After,theHMAisspreadand�inished.Finally,themixturereceivesthe�inalcompaction.
Figure 10. Asphalt surfacing model in Simul8
Fortheveri�icationofthebene�itsoftheproposedapproachincomparisonwiththerealoper-
ation,itwasproposedacostfunction,whichwasbasedonthecycletimeobtainedbythesim-
ulationmodel.Theunitcostsofearthmovingandpavingservicesaremultipliedbythecycle
time,givingthecostofeachscenario.Havingthecostsoftheproposedscenarios,onecancom-
parethebene�itsoftheleanstrategieswiththecurrentoperationofthemodeledsystem.
4. CASE STUDY
Aimingtoperformavalidationofthedevelopedmodelaswellasmeasurethebene�itsofthe
proposedapproach,realdatawasgatheredformarealcase.Thecasestudyisrelatedtoahigh-
wayconstruction,locatedintheNortheastregionofBrazil,withatotalextensionof32,1Km.
Forthepavingexecution,itwasconsideredasub-basewithnaturalmaterialofborrowpits
nearthetrack.Inthebaseexecution,itwasusedmaterialfromaborrowpitlocated6.6kmaway
fromtheaxisofthetrack,withamixtureof30%ofgravel.Theexecutionofthemixturemust
beperformedinasoilmixer.Thepavementlayershavethefollowingthickness:surfaceof5cm
(HMA),baseof15cmandsub-baseof20cm.Themaindatausedinthemodelingispresented
intheTable1.
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Table 1: Main volumes and distances adopted in the models
Project data Adopted value
Volume of materials (earthmoving) 3.602 m³
Volume of materials (sub-base) 1770,42 m³
Volume of materials (base) 1.142 m³
Volume of HMA (paving) 209,86 m³
Average transporta�on distance (earthmoving) 4,63 km
Distance between the borrow pit and the soil mixer 17,06 km
Distance between the soil mixer and the track 6,65 km
Inthesesimulations,someassumptionsweremade.Takingintoconsiderationthattheactiv-
ityofprocessingthematerialsinthesoilmixeriscontinuous,the�irstassumptionisthatatthe
momentatruckneedstobeloaded,thematerialisavailable.TheproductionofHMAisconsid-
eredcontinuousforthesamereason,thereforethesecondassumptionisthattheHMAisalways
availableforagiventruck.Thethirdassumptionisregardingtheloaders.Itisconsideredthat
theloadersaregoverningtheproduction,inordertoverifyifthereisthequeuesformationof
thetrucks.
Aimingtoevaluatethesystemperformance,weproposedsixindicators,whicharedescribed
asfollows:
a) Totalcost(R$):totalcostforearthmovingandpavingservices.
b) Totaltime(days):totalworktimerequiredfortheexecutionofearthmovingandpav-
ingservices;
c) T1:minimumwaittimeinthequeues;
d) T2:averagewaittimeinthequeues;
e) T3:maximumwaittimeinthequeues.
f) Totaltime(h):totaltimefortheexecutionofsurfacingservices.Itcanbeobserved
thatU$1,00isapproximatelyR$2,20(base-year2014).
Afterthedevelopmentofthemodelforthecurrentsystem,wereappliedsomeconceptsof
leanconstruction,suchasprocessoptimizationandminimizationoftheset-upactivities.The
initialmodelhasperformedtheactivitiesinalinearmanner,sothattheblockofactivitiesfor
the�illcompactiononlycouldbestartedwhenthetransportofmaterialshavebeen�inished.
Similarly,theblockofactivitiesoftransportofsub-basematerialsonlycouldbestartedwhen
the�illcompactionhasbeen�inishedandsoon.
Thesimultaneityoftheactivitieswasmodeledinthefollowingmanner:theblockofactivities
forthesub-basesystemsonlycanbeginwhentheearthmovingblockis�inished.Inthemodel,
itwasenabledthatsubsequentactivitiescanbeperformedinparallelwhenagivenpercentage
valueofthepredecessoractivitywasperformed.Reducingthesedelaysbetweentheactivities,
thecycletimecouldbereducedwiththemaintenanceofthesamepoolofmachines.
IntheTable2and3arepresentedtheminimum,averageandmaximalwaitingtimesforthe
dumptrucks in thequeues,aswellasthedurationofeachstageconsidered in themodeled
processes,inthemodels2and3,respectively.Themodelswererun20timesfortheobtaining
ofthepresentedresults.Themaindifferencebetweenmodels2and3consistsinthefactthat
inthemodel3thebaseactivitywasdividedintotwoindependentparts.Therefore,itispossible
theexecutionofapartofthebaseconcomitantlywithotherprocesses,reducingthetotalexe-
cutiontime.
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Table 2: Waiting times in the queues obtained by the Model 2
Ac7vity Dura7on
(h) Equipment
Minimum
wai7ng 7me in
the queues
(min)
Average wai7ng
7me in the
queues (min)
Maximum wai7ng
7me in the queues
(min)
Ea
rth
mo
vin
g Loading, hauling, unloading and
return. 85,61
Backhoe
6,71 16,44 30,23 Dump truck
Leveling and compac�on 16,08
Grader
- - - Sheep foot roller
Sub
-ba
se Loading, hauling, unloading and
return. 33,78
Backhoe 1,57 11,82 22,46
Dump truck
Leveling and compac�on 11,25 Grader
- - - Sheep foot roller
Ba
se
Cut from borrow pits and transport
for soil mixer 92,81
Backhoe 21,07 69 113,97
Dump truck
Aggregates distribu�on and
compac�on 11,67
Dump truck
- - - Tandem vibra�ng
roller
Surf
aci
ng
HMA produc�on, spreading and
finishing, final compac�on of the
mixture.
2,33
Pavers - - -
Tandem vibra�ng
roller - - -
Total �me with the overlapping of
the ac�vi�es 215,4 h 27 days
Total �me without the overlapping
of the ac�vi�es 253,5 h 32 days
Table 3: Waiting times in the queues obtained by the Model 3
Ac7vity Dura7on
(h) Equipment
Minimum
wai7ng 7me in
the queues
(min)
Average wai7ng
7me in the
queues (min)
Maximum wai7ng
7me in the queues
(min)
Ea
rth
mo
vin
g Loading, hauling, unloading and
return. 85,61
Backhoe
6,71 16,44 30,23 Dump truck
Leveling and compac�on 16,08 Grader
- - - Sheep foot roller
Sub
-ba
se Loading, hauling, unloading and
return. 33,78
Backhoe 1,57 11,82 22,46
Dump truck
Leveling and compac�on 11,25 Grader
- - - Sheep foot roller
Ba
se
Cut from borrow pits and transport
for soil mixer 93,03
Backhoe 21,07 69 113,97
Dump truck
Load in soil mixer, transport and
unload
49,70 Dump truck 0,7 15,29 30,58
Aggregates distribu�on and
compac�on 11,67
Dump truck
- - - Tandem vibra�ng
roller
Surf
aci
ng
HMA produc�on, spreading and
finishing, final compac�on of the
mixture.
2,33
Pavers - - -
Tandem vibra�ng
roller - - -
Total �me with the overlapping of
the ac�vi�es 137,7 h 22 days
Total �me without the overlapping
of the ac�vi�es 303,5 h 38 days
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ThesimulationresultsarepresentedinTable4.Analyzingtheabovementionedresults,one
canobservethatthereisaclearadvantageintheemploymentofrationalizationtools,suchas
theleanconcepts,inearthmovingandpavingservices.
Table 4: Simulation results
Model 1 Model 2 Model 3 ΔModel 2 (R$) ΔModel 3 (R$) ΔModel 2 (%) ΔModel 3 (%)
Total cost (R$) 359.127,84 257.621,78 277.445,47 101.506,07 -81.682,37 -28,3 -22,7
Total �me (days) 32,0 27,0 22,0 -5,0 -10,0 -15,6 -31,3
Ea
rth
mo
vin
g
T1(h) 25,71 6,71 6,71 -19 -19 -73,9 -73,9
T2(h) 42,28 16,44 16,44 -25,84 -25,84 -61,1 -61,1
T3(h) 59,81 30,23 30,23 -29,58 -29,58 -49,5 -49,5
Sub
-Ba
se T1(h) 19,71 1,57 1,57 -18,14 -18,14 -92,0 -92,0
T2(h) 32,77 11,82 11,82 -20,95 -20,95 -63,9 63,9
T3(h) 44,76 22,46 22,46 -22,3 -22,3 -49,8 -49,8
Ba
se T1(h) 45,93 21,07 21,07 -24,86 -24,86 -54,1 -54,1
T2(h) 124,23 69 69 -55,23 -55,23 -44,5 -44,5
T3(h) 191,84 113,97 113,97 -77,87 -77,87 -40,6 -40,6
Surf
aci
ng
Total
�me (h) 2,33 2,33 2,33 0,0 0,0 0,0 0,0
Takingintoaccounttheresultsobtainedinthesimulations,itshouldbehighlightedthedif-
ferencesbetweentheModel1(withoutleanconcepts)andtheModels2and3(withleancon-
cepts).TheModel2presentedareductionof15.6%intheconstructionexecutiontimeanda
reductionof28.3%inthetotalcost,incomparisonwiththeModel1.TheModel3presented
reductionof31.3%intheconstructionexecutiontimeandareductionof22.7%inthetotalcost,
incomparisonwiththeModel1.
Regardingtheasphaltsurfacing,onecanobservethat theModels2and3donot incur in
improvementintermsofconstructiontimes.Thisisduetothefactthatthisprocessisessen-
tiallysequential,aswellasthefactthattheproductionofHMAwasnotmodeled.Thus,there
arenoinef�icienciesthatcouldbemitigatedbytheleanconcepts.
Itisclearthattheproposedapproachisapowerfuldecisionsupporttool,beingvaluablefor
theplannersinthedecision-makingprocess.Withthediscreteeventmodelsproposed,several
scenariosandoperationalpoliciescanbepreviously tested,enablingthedecisionmakersto
developef�icientstrategiesfortheearthmovingandpavingactivities.
5. CONCLUSIONS
Thesimulationmodeldescribedinthispaperisapowerfultechniqueforplanningtheopera-
tionsofearthmovingandpavingservices,enablingtheimplementationofleanconceptsinthe
productiveprocesses.Theproposedmodelallowstheobtainingofrationalizedoperationalpol-
icies, incurring inreductionsofcycle times,equipmentutilizationrates, resourceutilization
ratesandqueuesformation,amongothersperformanceindicators.
Itcanbehighlightedthat,althoughtheproposedapproachenablesoperationalstrategies
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TRANSPORTES | ISSN: 2237-1346 140
withcostreductions,thesecostvaluesdoesnotrepresenttherealcostoftheconstruction,be-
causetheydonotconsiderthelaborcosts.Intheappliedunitcostsforeachservice,onlythe
equipmentcostsareconsidered.
Itisworthyofnotethatthestretchadoptedinthecasestudyisanalmostplainterrain,with
littlevariationinthecrosssection.Anotherfeatureofthecasestudyisregardingthedistance
betweentheanalyzedstretchandtheborrowpitsandsoilmixer,whicharevirtuallyidentical.
Thismeansthattheobtainedresultsarespeci�icforthissituation.Thereisnoguaranteethat
othertopographicalorgeotechnicalfeaturescanleadtoreductionsofthissamemagnitudeor
leadtoreductionsatall.Eachsituationneedstobemodeledandsimulated.
Alimitationofthestudyisthelackofrealdataontheperformedoperationaltimesinthe
studiedconstruction.Withoutthesedata,theauthorswerenotabletovalidatestatisticallythe
proposedmodel.However,accordingtoauthors’experience,theproposedmodelre�lectswell
therealsystem.
Intheproposedmodeling,couldbesimulateddifferentlocationsandsizesofthesoilmixer,
aswellasdifferentcuttingplacesforbasedependingofthesectionoftheroad.Otherservices
necessaryforthehighwayconstruction,suchasdrainage,specialartworksandhorizontalroad
markings,enablingabetterevaluationoftheimprovementsobtainedbytheleanconceptsap-
plication.
Intheproposedapproach,thereisnoconsiderationofqualityandsafetywhencomparing
theleanandnon-leanmodels.Otherperformanceindicatorswhichre�lecttheseaspectsneed
tobedevelopedandembeddedinthesimulationmodel.
Asafurtherdevelopmentoftheworkpresentedinthispaper,theauthorsarecurrentlywork-
ingintheintegrationofdiscreteeventsimulationmodelsandmixedintegerprogrammingmod-
els,aimingtheevaluationoftheleanpoliciesintegratedwiththeoptimaldistributionofmate-
rials,aswellasintheextensionoftheproposedapproachindrainageandmaintenanceser-
vices.Inaddition,theconsiderationoftanktruckandaeratorforcorrectingthesoilmoisture,
theapplicationofasphaltprimingonbaseandsub-base,aswellastheconsiderationofclimatic
aspectscouldbeaddedintheproposedmodel.
ACKNOWLEDGEMENTS
ThesupportoftheNationalCouncilforScienti�icandTechnologicalDevelopment(CNPq)isacknowledgedandappreciated.
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