Construction Project Management
Planning & Scheduling
Bar Charts
Building a CPM Schedule
Networks & Logic
CPM Scheduling
Logic Relationships & Precedence Networks
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Logic Linking Example With Lags

Building on the previous lesson, Saleh adds a twist with some activity lag. In this example, he discusses how part of an activity can be critical.

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So, we're going to take now example two with a little twist put on example one. It's the same three nodes, or three activities, same three relationships...or two relationships, sorry, but we're going to put a 6 days lag here, and a 1-day lag here on this relationship. What does that mean? It means B can start at least 6 days after the start of A, and C can start 1 day after the start of B. So, let's do the forward path's calculations and the backward path's.

Again, A is 0 and 10. Nothing changed. But B, now, has to start 6 days after the start of A, which is day 0 plus 6, plus 5, it can finish on the 11th. That's the early finish. For C, it can start one day after the start of B, so it's going to be 7 plus 3, 10.

Now we need to do the backward path's, and again, we take the latest of these finish dates, 10, 11, 10, so it's 11. The project should finish no later than the day 11. Minus 3, it is 8. This one, also, 11 minus 5, it is 6. This one is 11 minus 10. It is... Well, here's a problem. If I would say 11 minus 10, it's 1. It will be a problem. Why is that? Because this relationship means B cannot start until 6 days after the start of A.

So, if we take day 1 plus 6, B cannot start until day 7. 7 plus 5 is 12, so it is impacting the project. So, we would find out that because of this, A has to finish no later than day 10. Otherwise, it will delay...

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