AdvancedTopic 101 of 112Civil & Structural
CPM and PERT
Network methods identify the critical path of activities.
In depth
Critical path method models activities and dependencies in a network; the critical path is the longest path and determines project duration; float measures flexibility. PERT uses three-point estimates te=(a+4m+b)/6 for uncertain durations. Updated as the project progresses.
Key points
- Forward and backward pass
- Free and total float
- Resource levelling
ExampleA 12-month project has a critical path of 12 months; others have float.
What is CPM and PERT?
Network methods identify the critical path of activities.
Why is it important to understand CPM and PERT?
Critical path methods show which activities control the project duration, so managers can focus effort where delay matters most.
What is the critical path?
The longest sequence of dependent activities through the network, and any delay in it delays the whole project.
What is float?
The amount of time an activity can slip without delaying the project, and activities on the critical path have zero float.
How is CPM and PERT used in practice?
Typical applications include finding which activities determine the completion date of a building project, deciding where to add resources to shorten a schedule and using PERT estimates to show the risk of a late finish.
What should I learn before CPM and PERT?
Study "Construction project management" first (topic 100 of 112 in Civil & Structural). It covers the groundwork this topic builds on.
What are the key points of CPM and PERT?
Forward and backward pass. Free and total float. Resource levelling.
Can you give an example of CPM and PERT?
A 12-month project has a critical path of 12 months; others have float.
What comes after CPM and PERT?
The next topic is "Estimating and costing", which builds directly on this one.
How difficult is CPM and PERT?
It is classed as Advanced in Civil & Structural (topic 101 of 112). It is an advanced topic. It assumes you are comfortable with the intermediate topics in Civil & Structural.