cost modelling.pdf
TRANSCRIPT
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CONSTRUCTION
Fara DivaMustapaDepartmentofQuantitySurveyingUTM
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COSTMODELLING
Whatis
cost
modelling?
Historicaldevelopmentofcost
modelling
Purposesofcostmodelling
A roaches to cost modellin
Typesofmodel
Othercostmodellingapplications
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MODELS
ETHNICMODELFEMALEMODEL CAR MODEL
MATHEMATICAL
MODELSTATISTICALMODEL
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MATHEMATICALMODELS
MATHEMATICALMODELVIRTUALMODELREAL
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INTRODUCTION
Basic definition of model: A procedure developed to reflect by
means of derived process.
n anot er wor s, mo e s represent t e rea s tuat on n anot er
form, or asmaller scaleThe aim of cost models generally is to represent accurately the
improved forecasts and/or design optimisation.
Industry Practice
Industryisaboutto
manufactureanewproduct
Solve3DimensionalProblems
EstimateCostofProduction
Identifytoolsrequiredforproduction
Hebuilds
aprototype
Testproductsmarketability
Providesampleasevidenceofquality
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AIMOFCOSTMODELLING
To
stimulate
a
current
or
future
scenario
in
such
a
waythatdecisionmakerscanmadeuseoftheresults to decide their investment decision. This willalsohelpsthedesignersoptimise theirdesign
incorporated
with
cost
planning
and
cost
control
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INTRODUCTION(contd)
sone
o
emeasures
o
e
unc onan
per ormance
o
a
u ng,
AndshouldbecapableofbeingModelledinorderadesigncanbeevaluated.
Type ofmodel Form
1PHYSICAL 3DArchitectsModel
2
MATHEMATICAL Equation
3STATISTICAL Informationindicatingtrends
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INTRODUCTION
Construct
models
that
will
help
in
the
understanding
and
prediction
of
Cashflow
thecost effectonchangingdesignvariables
CostModellingmybedefinedasthesymbolicrepresentationofasystem,
ComponentThe
MODEL
DesignVariables
Constructionmethod
time
CostItems
Simulateacurrentorfuturesituationinsuchawaythatthesolutionsposed
InthedecisionMakingprocessofdesign
Estimatingthecostofabuildingdesignatanearlystagetoestablisheditsfeasibility
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TECHNIQUES
DEVELOPMENTOFFORECASTING
EstimatingAccuracyonaConstructionProjectPRE
60s
BillofQuantities
Approximate
Estimate
+/
60s CostPlanning
CostAnalysis
ElementalBills
70s CostModelling
CostInUse
Formulae(Price
80s LifeCycle Costing
CostData
ValueEn ineerin
Final
AccountTenderCONSTRUCTIONDESIGN CostEngineering
Accuracyin
Forecasting
90s ExpertSystems
QualitySystems
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DevelopmentstagesforModel
en y
e
ro em
CollectionofData
AnalysisofData
ModelBuilding
Opt mumMo e
EvaluateTheModel
Testing
ApplicationNewData
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COSTMODEL
CRITERIAS FORAGOODMODEL
1 Data requiredfreelyavailable
nappropr ate orman amount
(Qualityof
cost
advice
=Quality
&
Quantity
of
Data)
2 Allowanceforcontinuous updating(Newdata)
3 Evolvetosuittheneedsofchangingsituation
e.g. Construction Technology
4 Costmodelling process Quick,Cheap&Efficient
5 Accurate&Reliable
Representwhatit attemptstopredict
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DO THEY WORK?
1 YES The industryneedtobealittlelessconservative&protectionist
toitsintroductionforpracticaluse
2 NO Nothingfurther needtobedone.
3 NO Itappears
so
far
from
the
work
done
so
far,
given
time
and
the
,
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TYPESOFCOSTMODEL(TRADITIONALMODEL)
1 BRIEF STAGE Cost PerBed
Cost/Student
2 SKETCHDESIGN
SPACE
Cost/m2of
GFA
Cost/m2ofFunctionalSpace
Cost/m3ofBuildin Volume
3 DETAILEDDESIGN
ELEMENT
CostofFunctionalElement
expressed/m2 ofGFA
4 CostofGrou SMMitems
FEATURES (Abbreviated Quantities)
5 WORKING
DRAWINGS SMMITEMS
BillofQuantities
6OPERATIONS
Costper
Network
Operation
7 CostofLabour,
,
Source:TraditionalCostModelling
CostPlanning
&
Buildings
DouglasFerry,PeterBrandon
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OBJECTIVES OFCOSTMODEL
PartoftheStrategicDecisionMakingProcess
1 Give confidencetotheClient:ExpectedCostofhisproject
2 AQuick
Development
of
arepresentation
of
building
ItsCostcanbetestedandanalysed
3 Establishasuitablesystemforadvisingdesignersoncost
buildupofdesign.
mannerinwhichcostsaregeneratedandcontrolledonsite.
Dealwithcostofresourcesatanearlystage.
5 Theresults
of
the
model
should
allow
the
designer
to
incorporatethisknowledgeintothedrawings,specifications
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TYPESOFCOSTMODEL
ESTIMATING ApplicationofAppropriateComputerisedThe
A
PROPOSEDBUILDING
TO
MeasuredFinished
Quantities
OfProposedProject
TraditionalMethods
SuccessfulEstimating
Requires
hugeamount ofData
Improved
Techniques
ForUseatthedesi nsta e
(CostPlanning)
eve op ew e o o
PriceForecasting.
UseComputerstoManipulate
DatawithComplex
COST
MODELSa ema ca ormu ae
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TYPESOFCOSTMODEL
DETERMINISTIC
MODEL
Values canbeattributedtoallVariables
(Variablesareknownorcanbepredicted
Exactly
BUILDING PROBABILISTIC
MODEL
Valuesofsomevariableswillbe
uncertainandcanbeonlyestimated
(UseconceptsfromProbabilityTheory)
1 EMPIRICALMODEL
3 SIMULATION
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EMPIRICALMODEL
Basedon
observation,
experience
&
intuition
DevelopedonthebasisRightFeeling
,
PhysicalAppearanceofthebuilding
MethodsofConstructionDevelopa
Modelto In terms of Descri tions
Specification
Generate
Cost
&Dimensions
RelateQuantitiesToCost
Measurement
(Standard
Method
of
Measurement)
Informationmade
available
Visuallybywayofdrawings
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EMPIRICALMODEL
BILL
OF
Think
in
terms
of
ALGEBRIC
Terms
(Quantity
&
Cost)
QUANTITIES
P=LX WXDXR=
Plan
Plan
Rate
Exam le: ECA
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REGRESSIONANALYSISMODEL
ATechniquethatwillfindaformulaormathematicalmodelwhichbestdescribed
.
1 SimpleLinear Quantifyrelationship Plotted Graphically
2 MultipleRegression
Analysis3or
more
variables Use
of
Computer
Solutions
Total Y=ax+b2 VARIABLES
Cost
FloorArea
MULTIPLEVARIABLES
Construct on
Cost f(FloorArea,Storey Heights,ProcurementMethod,ContractPeriod,=
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SIMULATION
Whatisit?
1 Acomplexmathematical modelthatisconductedonthecomputerthat
re resentacom lex buildin s stem.
2 Conductedalmost totally
using
computer
programme
UseMonteCarloTechniquebasedonthegeneralideaofusingsamplingto
estimatedesiredresult.
4 Theprocessofbuilding simulationmodelinvolvesformulatingasetof
relationshipsbetween
the
variables
included
in
the
model
5
Reason tousesimulation:
Avoid directExperimentation(developing&Testingparticularsystem)
SolutionpurelyMathematicalModel
row areao pera ona esearc
6
UseofSimulation
CostManagement
ons ruc on s ma ng os orecas ng
Construction Planning
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EXPERTSYSTEM
Artificial
Intelli ence
AI
Robotics
AcomputersystemwhichbehavelikeExperts(QuantitySurveyor)
PickupthebrainsofalltheExpertsandcarefullystoreallthe
personsrules
of
thumb
in
the
computers
memory.
Example
1990
TheAlve
Pro ect,
Salford
Universit ,UK,
Professor
Peter
Brandon
TheLeadConsultantSystem(Elsie)
KnowledgefromExpertsinpracticebuiltintoasystemforuseonanumber
.
TheElsieKnowledgeBasedSoftwareEstimatingSystem
Builtaround4modelsofBudget,Procurement,Time&DevelopmentAppraisal
AbleToProduceEstimatefromNoDesign
AdaptivetoWhatIfFeature
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EXPERTSYSTEM(ELSIE)
BUDGET
Use minimalorNodrawnInformation
CatersfromComplexitiesofelementsqualities
Ex ressedinBCISFormat
DetailedAssumptionReport
ReportIncludes
advice
and
abreakdown
of
all
Elements
Evaluatesallmajorprojectcharacteristics&Clientpriorities
PROCUREMENT TestandRanksthe5MainProcurementMethods ReportsContainsdetailedexplanations&Reasoning
Forecast likelyproject
duration
TIME
ent es r t ca ct v t es n ases eas ty, es gn
Procurement,Construction&Commissioning)
Variationsexploredbychangingvariables
Re ortcontainsbreakdownofevents&Reasonin
DEVELOPMENT Adviceonviabilityofprojects
Derive &Test5ResidualValues(BuildingCost,profit,rentorsale,
APPRAISAL marketyield,landvalues ConstructionofCashflow.
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APPROXIMATE ANALYTICALCOSTMODELS
COMPARISON
1
Calculate
(Single Quantity)X
(AllinmeasuredRate)
Elementalbasis
(Individual
MeasuredItems)X
Appropriately
(Model Formulae)X
RatesGeneratedby
TheComputer
Analysed Rates
2Accuracy
13% 10% 1520%
(Depending onData)
3
Speed
1 Hour(singlepriced
method)
FewDays
(More
1Month
(ToComplete
Calculation)
Modelsdataalready
storedonthe
computer.
tobeinputwith
resultsinanhour
Cost
of
Calculation
QS
Assistants
tocomplete
data
input
5 Early Understoodand UsedbyEstimator Methodlargely
Usage usebygenerationsof
Surveyors
conversantwith
Techniques
unknown andnot
understood.
Reluctancetochange
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