CON 2001 Construction Methods Tool #1 - Construction Scheduling Presented by Elia Twigg, P.E. (Prof. Ralph V. Locurcio, P.E.)
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CON 2001
Construction MethodsTool #1 - Construction SchedulingPresented by Elia Twigg, P.E.(Prof. Ralph V. Locurcio, P.E.)
CVE 4070
Construction EngineeringTool #1 - Construction SchedulingPresented by Elia Twigg, P.E.(Prof. Ralph V. Locurcio, P.E.)
A little about me…
Scheduling Basics
What is scheduling? Tool to plan, monitor and record
progress
What are the benefits of scheduling? Forces pre-planning of project Graphical representation of project Helps manage resources
Scheduling…
Common methods: Bar/Gantt Charts Network Diagrams:
o CPM – Critical Path Methodo PERT – Program Evaluation & Review
Technique Velocity Chart or S-Curve Line-of-Balance Charts
Simple Bar Chart
1. Simple and easy to read2. Does not show interdependencies or critical path
Gantt Chart
1. Simple and easy to read2. Shows interdependencies 3. Can show critical path in a different view within MS Projects
CPM/PERT Chart
Velocity Chart or S-curve
1. Good for showing progress
2. Does not show task relationships or critical path
Excav Found Slab Struct Walls Roof Partitions Ceilings Paint CleanSchedule 100 225 275 575 975 1275 1725 1850 1950 2000Cum Hrs 88 218 268 568 768 993 1493 1493 1493 1493Plan Hrs 100 125 50 300 400 300 450 125 100 50Act Hrs 88 130 50 300 200 225 500
Simple Velocity Chart
0
500
1000
1500
2000
2500
Excav
Found
Slab
Struct
Wall
sRoo
f
Partiti
ons
Ceilin
gsPain
t
Clean
Schedule
Cum Hours
Plan Hours
Act Hours
Line-of-Balance Chart
1. Used for production line activities
2. Shows inter-dependencies
3. Does not show critical path
AA
CC
BB
AA Between house numbers
BB Activity time
CC Lag time between activities
Scheduling Programs…
Microsoft Project Easy to use Multi-format
o Network Diagram – shows CPMo Gantt Chartso Resource tracking
Excellent for small projects Relatively inexpensive Several other products on market
Primavera Used for large projects More flexible than MS Projects Includes resource & budget Includes database for tracking submittals Requires more capable computers Generally requires trained operator
Scheduling Programs…
Scheduling…
Tasks are not all consecutive Think of the WBS (major tasks and sub-tasks) Example – Road work and Drainage work
Project Managers need to: Identify tasks & timing Identify task interdependencies Identify critical path Identify slack/float and lag times Chart progress & payment
Tasks & Timing… Any single, identifiable & measurable work step
in the total project WBS
A “time consuming” task
Two conventions: Activity on Arrow… AOA networks
Precedence diagrams (MS Projects)
Activity on Arrow…
3 5 7
2 4
1
Activity Name Duration 1-3 Sign Contract 3 1-2 Obtain Permits 5 3-5 Excavation 7 5-7 Form Foundation 10 2-3 Survey Utilities 2 2-4 Layout Foundation 3 4-5 Deliver Forms 1 7-8 Pour Foundation 1
Sign Contract
Obtain Permits
Excavation Form FoundationSu
rvey
Util
ities
Layout Foundation
Del
iver
For
ms
3 7 10
5 2 1 1
38
Pour
Foundation
Precedence diagram…
Activity Duration Float
Sign Contract 0
Obtain Permits 5 0
Survey Utilities 2 0
Excavation 7 2
Layout Foundation 3 0
Deliver Forms 1 2
Form Foundation 10 3
Pour Foundation 1 0
Signcontract
Obtainpermits
ExcavationForm
Foundation
Survey Utilities
Deliver Forms
Layout Foundation
Pour Foundation
Task Interdependencies…
Finish-to-start (FS): Succeeding activity (Activity B) may not begin UNTIL the
preceding activity (Activity A) is completed Most common or conventional relationship Example…
You cannot begin constructing walls on a house until the foundation has been constructed.
Finish-to-start
Activity A
Activity B
Task Interdependencies…
Start-to-start (SS): Successor (Activity B) cannot start UNTIL predecessor (Activity
A) begins Very common and useful, often includes a lag time Examples…
As soon as “Clearing & Grubbing” starts, the “Excavation” can start Voting for the President - As soon as votes start coming in, they can begin
Activity B, which is to tally the results.
Start-to-start
Activity A
Activity B
Task Interdependencies…
Finish-to-finish (FF): The activity must finish at the same time as a preceding activity Infrequently used Example…
Cooking a meal – All items you cook may have different durations, however, if you want all items to be done at one time, this would represent a finish-to-finish example.
Activity A
Activity B
Finish-to-finish
Task Interdependencies…
Start-to-finish: The activity may not finish until the predecessor starts Infrequently used, not really practical to schedule Example…
You have an exam scheduled for 11am. You determine you will cram for exam 3 hours before. You arrive in class and instructor showed up a bit late, you continue to cram until the test paper hit your desk. What determined the finish of your study time? The professor stating all study material must be put away.
Start-to-finish
Activity A
Activity B
Critical Path Critical Path
Longest path through network Determines the duration of project Shortest amount of time necessary to complete the
project
Slack/Float & Lead/Lag Times… Slack or Float - Measured within activities The difference between the latest allowable date and earliest
expected date for any given task
Lead or Lag Times - Measured between activities
Finish-to-start w/lag
Activity A
Activity B
Start-to-start w/lag
Activity A
Activity B
Finish-to-finish w/lag
Activity A
Activity B
Start-to-finish w/lag
Activity A
Activity B
Slack/Float & Lead/Lag Times…
Slack or Float - Measured within activities
Lead or Lag Times - Measured between activities
Bus Shelter Example
Scheduling Process Steps…
1. Identify key work elements (WBS)
2. Establish logical order of tasks
3. Estimate time durations for each
4. Determine precedence/dependency
5. Display in graphical/network format
6. Enter lead or lag time
7. Check network timeline
8. Add percent complete for project status
9. Convert to PERT chart
10. Explore other variations… tutorial included with software.
Identify Key Work Elements
Identify work elements… Responsibility: prime vs. subs… Crew or craft: carpenters, plumbers, electrical… Use of equipment: dozer, dumps… Materials: concrete, steel, masonry… Subdivision of work: foundation, walls… Location of work: site A, site B… Breakdown in specs or for payment; i.e. CSI format Contractor’s bid & payment elements Other factors: like outage schedules, utilities
Really depends on the contract, the controls being used, and the owner’s requirements
Estimate time durations for each
Establish logical order of tasks
Determine precedence/dependency
DoubleClick
Another way to determine precedence/dependency
Lag Time
100% Complete
DoubleClick
60% Complete
Select Network Diagram
Red indicates the Critical Path
Homework #3
Using MS Project Create a Gantt chart Follow all instruction on Assignment Bring to class for review & correction Due:
Loading MS Project
Test #1 - Review
That’s all for today…BUT
STOP!!!!
Do not take the test home… turn it in before you leave
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