Total Float Definition Calculation

The first type of float encountered is Total Float. Total Float is defined as the amount of spare time available to an activity if all preceding activities are started as early as possible and all following activities are started as late as possible. It is calculated as follows:

Figure 3-14. Tabulation Solution of Data

Activity Critical

Description I J DUR ES EF LS LF Path

Figure 3-14. Tabulation Solution of Data

Activity Critical

Description I J DUR ES EF LS LF Path

A

1

3

5

0

5

0

5

#

B

1

5

2

0

2

3

5

C

1

7

4

0

4

3

7

D

3

11

3

5

8

6

9

E

3

9

4

5

9

5

9

*

F

11

17

5

9

14

g

14

*

G

9

17

2

9

11

12

14

H

5

13

6

2

8

5

11

J

7

13

3

4

7

8

11

K

7

15

5

4

9

7

12

L

13

19

2

8

10

11

13

M

15

19

1

9

10

12

13

N

13

17

3

8

11

11

14

0

17

21

5

14

19

14

19

#

P

19

21

6

10

16

13

19

Calculations for each activity Forward Pass = Early Start (ES)

Backward Pass = Late Finish (LF) Early Finish (EF) = ES + Duration Late Start (LS) = LF - Duration

Calculations for each activity Forward Pass = Early Start (ES)

Backward Pass = Late Finish (LF) Early Finish (EF) = ES + Duration Late Start (LS) = LF - Duration

Consequently, from this definition it becomes obvious that TF for Critical Activities equals zero.

The network defined was a simple one and the Critical Path was easily identified, however, in complex networks, calculation of total float by activity may become the only way to locate the Critical Path.

Figure 3-15. Tabulation Solution of Data

Activity Description

DUR ES

EF LS LF TF

Critical Path

Activity Description

DUR ES

EF LS LF TF

Critical Path

A

1

3

5

0

5

0

5

0

*

B

1

5

2

0

2

3

5

3

C

1

7

4

0

4

3

7

3

D

3

11

3

5

8

6

9

1

E

3

9

4

5

9

5

9

0

*

F

11

17

5

9

14

9

14

0

*

G

9

17

2

9

11

12

14

3

H

5

13

6

2

8

5

11

3

J

7

13

3

4

7

8

11

4

K

7

15

5

4

9

7

12

3

L

13

19

2

8

10

11

13

3

M

15

19

1

9

10

12

13

3

N

13

17

3

8

11

11

14

3

0

17

21

5

14

19

14

19

0

»

P

19

21

6

10

16

13

19

3

Calculations for each activity

Forward Pass Backward Pass Early Finish (EF) Late Start (LS) Total Float (TF)

Early Start (ES) Late Finish {LF) ES + Duration LF — Duration LF — EF

Problem 3-6: Total Float

Given the data on Figure 3-14 and the formula TF= LS — ES or LF — EF, calculate total float for each activity.

Analysis

Figure 3-15 shows the solution for the total float.

Activity Description

Figure 3-16. Tabulation Solution of Data

Critical

I J DUR ES EF LS LF TF FF Path

Activity Description

Critical

I J DUR ES EF LS LF TF FF Path

A

1

3

5

0

5

0

5

0

0

#

B

1

5

2

0

2

3

5

3

0

C

1

7

4

0

4

3

7

3

0

D

3

11

3

5

8

6

9

1

1

E

3

9

4

5

9

5

9

0

0

*

F

11

17

5

9

14

9

14

0

0

*

G

9

17

2

9

11

12

14

3

3

H

5

13

6

2

a

5

11

3

0

J

7

13

3

4

7

8

11

4

1

K

7

15

5

4

9

7

12

3

0

L

13

19

2

8

10

11

13

3

0

M

15

19

1

9

10

12

13

3

0

N

13

17

3

8

11

11

14

3

3

0

17

21

5

14

19

14

19

0

0

*

P

19

21

6

10

16

13

19

3

3

Calculations for each activity

Forward Pass Backward Pass Early Finish (EF) Late Start (LS) Total Float (TF)

= Early Start (ES) = Late Finish (LF) = ES + Duration = LF — Duration = LF - EF or

Calculations for each activity

Forward Pass Backward Pass Early Finish (EF) Late Start (LS) Total Float (TF)

Free Float {FF)

= Early Start (ES) = Late Finish (LF) = ES + Duration = LF — Duration = LF - EF or

Free Float {FF)

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