👉Program Evaluation and Review Technique (PERT)

🔍 What is PERT?

⏺The Program Evaluation and Review Technique (PERT) is a project scheduling method that helps managers handle uncertainty in estimating task durations.

⏺It was developed by the U.S. Navy in the 1950s for the Polaris submarine project and has since been widely adopted in construction and engineering.

▶️Unlike the Critical Path Method (CPM), which assumes known activity durations, PERT is probabilistic,meaning it deals with variability in how long tasks may take.

🧠 How It Works

⏺PERT uses three time estimates for each activity:

𝗢𝗽𝘁𝗶𝗺𝗶𝘀𝘁𝗶𝗰(𝗢)-The minimum possible time to complete a task (if everything goes perfectly),Best-case scenario.
𝗠𝗼𝘀𝘁 𝗹𝗶𝗸𝗲𝗹𝘆(𝗠)-The normal time you expect the task to take,Based on experience.
𝗣𝗲𝘀𝘀𝗶𝗺𝗶𝘀𝘁𝗶𝗰 (𝗣)-The maximum time the task might take (if things go wrong),Worst-case scenario.

🔎 Why Use PERT in Construction?

⏺Construction projects often face uncertainties—weather, material delays, labor shortages, etc.

⏺PERT helps: Account for risks in time estimation Provide more accurate schedules Improve planning and decision-making

👉Network Diagramming in Construction Projects

⏺A Network Diagram is a graphical representation of a project’s activities and their logical relationships. It shows what comes first, what follows, and what tasks depend on others.

🏷There are two main types of network diagrams:

🧩 A. Activity-on-Arrow (AoA)
Also called the Arrow Diagramming Method (ADM).

✅ Features:

⏺Arrows represent activities Nodes (circles or events) represent milestones or the start/end of activities.

⏺Activities are defined by start and end points Often uses dummy activities (dashed arrows with zero duration) to show dependencies that cannot be represented otherwise.

🔰Dummy Activity:

⏺A placeholder arrow used for logic, not actual work. It helps maintain proper task relationships when two activities depend on a common predecessor.

📉 Limitations:

⏺Cannot easily represent lead and lag times
Less flexible than AoN for modern scheduling tools.

🧩 B. Activity-on-Node (AoN)
Also called the Precedence Diagramming Method (PDM),the most widely used in modern software like Primavera P6 and Microsoft Project.

✅ Features:

⏺Nodes (boxes) represent activities Arrows show dependencies or logic between them Allows for various dependency types:
Finish-to-Start (FS): Task B starts after Task A finishes
Start-to-Start (SS): Task B starts when Task A starts
Finish-to-Finish (FF): Task B finishes when Task A finishes
Start-to-Finish (SF): Rare—Task B must start before Task A finishes.

🧩 C. Precedence Diagram

⏺This is simply the visual representation of an Activity-on-Node (AoN) method. It maps out:

⏺All project activities
Their logical sequences
Critical paths and floats/slacks

📍Each box (node) contains:Activity name,Duration,Early/latest start and finish dates &Total float

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