Introduction to CPM Scheduling Chapter 5 CPM Shows

Introduction to CPM Scheduling Chapter 5

CPM Shows Construction Logic CPM= Critical Path Method You will get to know this style of diagram well Red arrows = critical path Variable start times • Early Start • Latest Start DUR= Duration DRAG = delay amount TF = Total float

Features of CPM 1. CPM shows the construction logic The arrows show relationships of logic An arrow leaving one activity and pointing to the other indicates that the first activity must be completed before the next activity can start Note the legend in the bottom left: ES= Early Start EF=Early Finish LS=Late Start LF=Late Finish Number below=Float Hotel Project – figure 5. 1 in text

Features of CPM 2. CPM Identifies the Critical Activities down the middle with bolded arrows • Have 0 days of float • This is what identifies them as critical • Their Early Start and Late Start dates are the same The hotel is scheduled to be finished on day 334 Hotel Project – figure 5. 1 in text

Features of CPM EXAMPLE If excavation is delayed or takes 5 days longer, The end day will be changed to 339 Because excavation is a critical activity If the pool takes 12 days longer to finish Will it cause a delay in the completion date? As long as it is finished by day 300 it will not Hotel Project – figure 5. 1 in text

Features of CPM EXAMPLE: If the Yacht Club contractor started on time, but took 60 days longer Is that contractor responsible for liquidated damages? He could have taken 172 days longer and not delayed the project He has 172 days of float Hotel Project – figure 5. 1 in text

Features of CPM If the Lobby Structure takes 5 extra days Which later activities must be accelerated to meet the original completion date? CPM shows managers which activities to focus on to meet the completion date. All activities do not need to accelerate to complete on time Hotel Project – figure 5. 1 in text

Pareto’s Law • Vilfredo Pareto, a gardener in Italy, observed that – 20% of the Italian people owned 80% of the wealth in Italy – While gardening he observed 20% of the pea pods produced 80% of the peas. • This became known as the 80: 20 rule “The vital few and trivial many rule” • Construction management problems – 80% are caused by 20% of who you manage • Your to-do list – 80% of your daily results come from 20% of the items on your list

Remember that 20% of your activity will product 80% of your results – Key is to identify the 20% and manage them carefully – The other 80% (trivial many) will just follow along

3. CPM helps determine effects of Change orders or delays Identifies if a change order will affect the completion date If a critical path activity has a delay or change, then the project completion date will be delayed unless something is done to the remaining critical activities to speed them up

4. CPM Allows Management to Set Priorities When many activities need the same equipment can manage who gets it first based by how many float days they have. Accurately determines when materials should be delivered

5. CPM Adapts to Any Project – Simple or Complex Previously it was common practice not to use CPM on projects smaller than $2 million Today’s software is friendlier More managers are familiar with CPM

6. CPM is Easy to Follow Visually It gives a vision of the whole project from beginning to end Forces higher thinking to prepare a CPM chart than for a bar chart It is the most effective scheduling and planning system that has been developed to date Note the word Slack is used instead of Float

7. CPM Allows Analysis of Different Methods Management can play what-if scenarios and see the potential outcome EXAMPLE: What if we bring in another crane? What if we double this crew? What if we work multiple shifts? What if we work weekends?

8. CPM is Useful for Court Cases Some companies use CPM for this reason alone To help keep them out of court They are tired of trying to prove who is responsible for delays Some of the biggest construction related lawsuits are related to delay claims A few days of delay in the fall can cause a delay of months due to winter weather CPM can work both ways—it can also show the effect of delays caused by the owner

9. CPM Creates Teamwork Everyone who looks at the logic diagram sees the same vision of the project. Everyone can see the importance of his or her part The team is encouraged to help develop the logic diagram Everyone needs to have a specific assignment The CPM diagram looks somewhat like a football play Everyone can see exactly what they are to do Everyone can see the effects of not fulfilling their assignment

10. Reasons CPM Not Used The construction industry was one of the first to adopt CPM Found it was difficult to learn Needed computers and software Few companies had computers Few subcontractors understood CPM Managers tended to print too many reports CHANGES: Computers commonplace Management is more skilled in CPM Software is more usable

Chapter 5 Worksheet On Canvas Due by next class period