Cost Modelling.pdf

8/10/2019 Cost Modelling.pdf

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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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Documents

Cost Modelling.pdf