ENGI 5708 Design of Civil Engineering Systemsspkenny/Courses/Undergraduate/ENGI5708/Lecture... ·...

Shawn Kenny, Ph.D., P.Eng.Assistant ProfessorFaculty of Engineering and Applied ScienceMemorial University of [email protected]

ENGI 5708 Design of Civil Engineering Systems

Lecture 18: Scheduling Models

2 ENGI 5708 Civil Engineering Systems – Lecture 18© 2008 S. Kenny, Ph.D., P.Eng.

Lecture 18 Objective

to examine concepts of scheduling models


Scheduling ModelsPurpose

Facilitate project management and coordination of project activities• Schedule• Resources• Cost

ApplicationWriting a paper or thesisAcademic term studyEngineering design projectsConstruction activities


Critical Path Method

Analysis TechniqueGraphical framework • Augment visual interpretation and ease of

applicationNetwork model analysis• Past lecture examined as a zero/one LP


Critical Path Method (cont.)

ObjectiveSchedule optimization for project activities• Timeline and duration of sequential and parallel

activities without affecting project durationOutcomes• Identify critical path

Longest project duration (shortest possible completion time)

• Identify total float timeAcceptable delay in specific activities without increasing project durationZero float time on the critical path


Activity Scheduling – Key StepsActivity List

Work breakdown structure• Definition, organization and hierarchy of project scope

outcomes (end goals)

Activity DurationProject timeline • Early/late start and finish of each activity

Activity DependencyLink among activities• Precedence • Sequence• Constraints


Work Breakdown Structure

Define and Organize Project ScopeDefines planned outcomes (end goals)Provides estimate of effortFacilitates project management and project scheduling


Work Breakdown Structure (cont.)

Does Not…Characterize system hierarchyDefine activities or relationships between activitiesEstablish schedule or chronological order


Work Breakdown Structure (cont.)

http://upload.wikimedia.org/wikipedia/en/e/e4/WbsConstruction.png


Arrow or Precedence Diagram

Activity Flow CharacterizationActivities displayed and sequenced with any dependenciesArrows• Specific activity

Nodes• Event or point in time

e.g. start/finish

• Connected by arrows (activity)

1 2Pour Foundation

Time 1 Time 2


Arrow or Precedence Diagram (cont.)

CharacteristicsWBS referenceNormal activity durationEarly start and early finish date Late start and late finish date



Importance?Tool for scheduling activities• Common

bar chart• Modified

bar chart (Gantt chart)

• Time-scaled arrow diagram

http://upload.wikimedia.org/wikipedia/commons/e/e2/GanttChartAnatomy.png



Node ConventionOne start node and one end node per arrow (activity) connecting nodesOrigin node has only outward pointing arrowsEnd node has only outward pointing arrowsNode Numbering• Origin node = 1• j-index > i-index node notation• End node maximum node number

Diagram CompactnessNo unnecessary nodes, arrows or dummy activitiesArrows should flow “to-the-right” as much as possible



Flow of Activities

Single activity

Precedent activities

Dual precedent activities



Dummy ActivitiesClarity on conditional or dependent activities• Activity A precedes C• Activity B precedes C• Activity B precedes D

Which diagram is correct?Why?



Dummy ActivitiesAvoids ambiguity• Activity A precedes B and B precedes D• Activity A precedes C and C precedes D

Which diagram is correct?Why?


Diagram Complete?

Example 18-01As part of a larger arrow diagram, a contractor wants to include the following activities related to construction of a foundation for a light commercial building:

A: order, wait, and receive steel sideformB: order, wait, and receive steel rebarC: excavate foundationD: place steel sideformE: place steel rebarF: pour foundation

1 3

A

4

2

5 6

B

C

E

D

F


Project CostBasic Project Element

On time, on budgetRequirements

Clear project objectives, WSB, deliverablesProject management protocolsChange control and managementOrganizational structure and communication

Cost OverrunPoor consideration of attributesScope creepTechnical, political, socio-economic


Cost-Duration CurvesDevelopment

Experience and DatabaseResource type and allocation

Normal TimeLeast cost to complete activity

Crash TimeMinimum completion time

tcrash tnormal

Activity Duration

Act

ivity

Cos

t


Cost-Duration Curves (cont.)

Crash TimeCompression• OT• ↑

crew size

• 3rd partyIncrease costQualitySafetyEfficiency

tcrash tnormal

Activity Duration

Act

ivity

Cos

t


Auxiliary Information

Creating a Gantt Chart in Excelhttp://office.microsoft.com/en-us/excel/HA010346051033.aspx


Auxiliary Information (cont.)Project Management – OpenProj

• http://en.wikipedia.org/wiki/OpenProj• http://openproj.org/openproj

Capabilities• Earned value costing • Gantt chart • PERT graph • Resource Breakdown

Structure (RBS) chart • Task usage reports • Work Breakdown

Structure (WBS)


Auxiliary Information (cont.)

OpenProj


Reading Listhttp://www.ce.cmu.edu/pmbook/10_Fundamental_Scheduling_Procedures.html

Key elements• Relevance of Construction Schedules• The Critical Path Method• Calculations for Critical Path Scheduling• Activity Float and Schedules• Presenting Project Schedules• Critical Path Scheduling for Activity-on-Node and with Leads, Lags,

and Windows• Calculations for Scheduling with Leads, Lags and Windows

http://www.ce.cmu.edu/pmbook/11_Advanced_Scheduling_Techniques.html

Key Elements• Crashing and Time/Cost Tradeoffs


References

http://en.wikipedia.org/wiki/List_of_project_management_topicshttp://www.ce.cmu.edu/pmbook/10_Fundamental_Scheduling_Procedures.htmlReVelle, C.S., E.E. Whitlatch, Jr. and J.R. Wright (2004). Civil and Environmental Systems Engineering 2nd Edition, Pearson Prentice Hall ISBN 0-13-047822-9

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