CON 2001 Construction Methods Tool #1 - Construction Scheduling Presented by Elia Twigg, P.E. (Prof....

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