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Operations Research




                    Notes
                                                         Figure  12.16:  Critical Path  of the  Project
                                                                  5  10          10 15
                                                   4  9
                                        T     T               1                5                     T     T
                                         E  L                                                         E   L
                                        0  0         2              4               9       7        22 22
                                                                                15 15
                                                4
                                                                                    2                  10
                                                             1                                  5
                                         1                                  7
                                                                                             8
                                              1                     8                 1
                                                             6
                                                     3               5      4      6             17 17

                                                1  1                7  7         11 16

                                   The critical path is 1-3-5-7-8-10 (shown in double line in Figure 12.16) with the project duration
                                   of 22 days.


                                          Example: The following Table 12.6 gives the activities in construction project and time
                                   duration.

                                                      Table 12.6:  Project  Schedule  with Time  Duration

                                            Activity           Preceding Activity        Normal time (days)
                                             1-2                     -                         20
                                             1-3                     -                         25
                                             2-3                    1-2                        10
                                             2-4                    1-2                        12
                                             3-4                   1-3,2-3                     5
                                             4-5                   2-4,3-4                     10

                                   1.  Draw the activity network of the project.
                                   2.  Find the total float and free float for each activity.
                                   Solution:
                                   1.  From the activity relationship given, the activity network is shown in Figure 12.17 below:

                                                         Figure  12.17:  Activity  Network  Diagram


                                                               2
                                                                        12
                                                      20
                                                                 10
                                                   1                          4               5
                                                                                     10
                                                     25               5
                                                               3





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