Standards of Practice Course

© Construction Management Association of America. Do Not Duplicate or Reproduce.

Standards of Practice Course

CPM Scheduling Lab

© Construction Management Association of America. Do Not Duplicate or Reproduce.

Activity Notation

Use for Manual Calculation

Early Start

Late Start

Early Finish

Late Finish

Duration

Activity ID

ES EF

LS LF

ID

D

FF TF

Free Float Total Float

April, 2010

© Construction Management Association of America. Do Not Duplicate or Reproduce. September, 2006

8 17

8 17

D

10

0 0

1 3

1 3

A

3

0 0

4 4

7 7

B

1

3 3

4 7

4 7

C

4

0 0

FS FS

EF = ES + D - 1

ES = EFP + 1

LF = LSS - 1

LS = LF - D + 1

TF = LF - EF FF = ESS - EF - 1

LFES EFLS

IDD

FF TF

Notation:

Subscripts:

S = Successor

P = Predecessor

Sample

April, 2010


CMAA Formulas for Calculationfor Finish-to-Start Activities

• ES = EFP + 1

• LS = LF - D + 1

• TF = LF - EF

• EF = ES + D – 1

• LF = LSS – 1

• FF = ESS - EF - 1

April, 2010


CMAA Calculation Tips

1. Start by taking note of the relationships. Notice which are not finish-start, or which ones are finish-start but with a lag. (Formulas don’t apply to Start-to-Start relationships or Finish-to-Finish relationships.)

2. Begin calculating on the first activity on the left side.3. In CMAA’s examples, the first activity begins on Day

One. Not Day Zero. 4. Work towards the right, in an up and down motion, in

strips (this is to avoid unnecessary iterations).

April, 2010


CMAA Calculation Tips

5. When working with a lag greater than 0, first calculate the link as if it had no lag. Then add the lag time.

6. When an activity has multiple predecessors, each predecessor must be evaluated in turn to determine the correct early start date for the successor. During the Forward pass, the greater # (latest date) overrides.

7. The same concept holds true during the backward pass. For activities which have multiple successors, each successor must be evaluated to determine the correct late finish date for the preceding activity. During the backward pass, the lesser # (earlier date) overrides.

8. The last activity has no successor, so the late date formulas don’t apply. Assume for the last activity, EF = LF = END.

April, 2010


D

10

1 3A

3

4 B

1

C

4

FS FS

EF = ES + D - 1

ES = EFP + 1

LF = LSS - 1

LS = LF - D + 1

TF = LF - EF FF = ESS - EF - 1

LFES EFLS

IDD

FF TF

Notation:

Subscripts:

S = Successor

P = Predecessor

Exercise #1

April, 2010


PART 1: Calculate a Baseline ScheduleThe AON logical network of a baseline schedule for a construction project is as shown in Exercise #2. Assume

that for the last activity EF=LF=end of project.

Required: Answer all questions on network diagram only

1. Calculate the ES, EF, LS, LF, and TF for each activity.2. What is the free float (FF) for activity E?3. What is the free float (FF) for activity F? Explain the

difference in days between the FF and the TF for activity F.

Exercise #2, Part 1

April, 2010


A10

D5

F10

G10

H5

E5

B10

C10

Exercise #2, Part 1

• All relationships finish-start unless noted.

FS + 2

FS - 2

LFES EFLS

IDD

FF TF

Notation:

SS + 5

April, 2010


Exercise #2, Forward Path

A

B

C

D

E

F

G

H

SS + 5

FS + 2

FS - 2

April, 2010


Exercise #2, Backward Path

A

B

C

D

E

F

G

H

SS + 5

FS + 2

FS - 2

April, 2010


Exercise #2, Part 2

PART 2: Calculating Progress on the ScheduleAt the end of the day on day 15, the following progress

information was available:

1. Activity A started 2 days late, and was completed on time.

2. Activity B started on time, and made progress as follows.

a. Completed work in place = 500 sq ft

b. Remaining work quantity = 500 sq ft

April, 2010


Exercise #2, Part 2

PART 2, Continued:

3. Activity D started on day 14. Remaining duration required for completion is estimated to be 2 days.

4. The original duration for Activity E changed from 5 days to 20 days.

April, 2010


Exercise #2, Part 2

PART 2, Continued:Required: Answer all questions on network diagram only

Based on the progress information available at end of day 15,

Q1. Calculate actual start and finish dates for all activities in progress.

Q2. Calculate the ES, EF, LS, LF, and TF for all other activities. Identify the critical Path.

April, 2010


Exercise #2, Part 2

• All relationships finish-start unless noted.

A10

D5

F10

B10

SS + 5

FS + 2

FS - 2

LFES EFLS

IDD

Notation:AS AF

Actual Start

Actual Duration

Dur = RD if AD>0

Dur = RD if AD=0 (activity has not started)

AD

Actual FinishFF TF

G10

H5

E20

C10

April, 2010


Exercise #2, Forward Path

A

B

C

D

E

F

G

H

FS + 2

SS + 5

FS - 2

Data Date – Day 16

April, 2010


Exercise #2, Backward Path

A

B

C

D

E

F

G

H

FS + 2

SS + 5

FS - 2

Data Date – Day 16

April, 2010

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Standards of Practice Course