Scheduling Flashcards
What does CPM stand for?
Critical Path Method
What are the 2 CPM diagrams?
Activity on Arrow and Activity on Node (AOA and AON)
What determines the project duration?
The critical path activities
What is Early Start (ES)?
Latest EF (early finish) of all IPA’s
What is Early Finish (EF)?
Early Start + Duration
What is Late Finish (LF)?
Earliest late start of succeeding activities
What is Late Start (LS)?
Late Finish - Duration
What is Total Float (TF)?
The time an activity can be delayed without affecting project completion (LS - ES)
What is Free Float (FF)?
The time an activity may be delayed without affecting the early start of any of the next immediate activities
What is Critical Path (CP)?
The longest interconnected path through the network which has a length equal to the project duration
What is the procedure for network calculations?
1) Do and forward pass and calculate all ES’s and EF’s
2) Do a backwards pass and calculate all LF’s and LS’s
3) Calculate floats
4) Determine critical path
For resource levelling, which activities are proceeded with first and given the most importance?
The activity with the earliest late start
What is Interfering Float (IF)?
The amount of time an activity can be delayed or extended from its ES without delaying the total float (TF)
What are the values for TF, FF, IF for critical path activities?
0
What does a negative total float (TF) represent?
Means you have to make up (save) that duration
For example if activity B has a TF of -3 then activity B must be cut short by 3 days in order to not disrupt the project completion date
What is an example of a non-network type of scheduling?
Gantt Chart
Why would a contractor want to crash a schedule?
To save time on a project
To save money on a project
To make up time on a project
What are the steps involved in schedule crashing?
1) Do a forwards and backwards pass
2) Identify critical path
3) Identify critical activities
4) Identify next longest path
5) Identify the activity with the lowest cost slope in critical path
6) Determine the physical limit and calculate the logical limit
7) Crash the activity with the lowest cost slope by the lower of the logical or physical limit
8) Recalculate the forward and backwards pass
9) Calculate indirect costs
10) Calculate total direct cost
What is direct cost?
Any cost that can be associated with a discrete physical part of a construction project
What is indirect cost?
Any cost that cannot be associated with a discrete physical part of a construction project
What is the physical limit?
The max number of days you can reduce an activity without making it impossible to complete
What is the logical limit?
The max number of days you can reduce an activity before creating another critical path
What is the formula for cost slope?
(crash cost - direct cost)/crash duration
