Limited resource allocation and smoothing

Limited resource allocation

When the amount of a resource (masons, excavators, cement, cash) available per day has an upper limit, the activities must be scheduled so that the daily demand never exceeds that limit. Activities are delayed (even beyond their float) if necessary, so the project duration may increase. Method (heuristic):

1. Draw the early-start schedule and find float of each activity.
2. For each day, add the demand of the activities that can start.
3. If demand is above the limit, give priority to the activity with the least float (smallest LST), i.e. critical ones first, and delay the others.
4. Update the schedule day by day until all activities are scheduled.

Resource smoothing

Resource smoothing adjusts non-critical activities within their float to reduce peaks, keeping the project duration. It is used when the duration is fixed (time-limited).

Application to a construction project

Example: A foundation excavation (3 days, 3 men), D footing after A (2 days, 2 men), B fencing (2 days, 2 men), C material shed (2 days, 3 men). Critical path A-D (5 days). Early start demand is 8 men on days 1-2.

Limit 5 men: A and B start on day 1; C (float 3 days) is moved to days 4-5 with D.

  5 |# #   # # 
  4 |# #   # # 
  3 |# # # # # 
  2 |# # # # # 
  1 |# # # # # 
    +----------
     1 2 3 4 5  day
     5 5 3 5 5  men

The duration remains 5 days, and the peak falls from 8 to 5 men.

Limit 4 men: A on days 1-3; B and D on days 4-5; C on days 6-7.

  4 |      # #     
  3 |# # # # # # # 
  2 |# # # # # # # 
  1 |# # # # # # # 
    +--------------
     1 2 3 4 5 6 7  day
     3 3 3 4 4 3 3  men

Now the duration increases from 5 to 7 days.

Used in building, road and canal works to decide gang size, equipment number and cash limits, and to find the realistic completion time.