This week we learned about scheduling and it’s importance in construction projects. In following with the flipped classroom we first learned about CPM (critical path method) and project networks out of class. Then in class, we applied what we learned by using CPM to layout the courses required to graduate with a civil engineering degree from a school similar to Mines.
In class we split into groups of two and completed the assignment using sticky notes and a pencil. My partner and I were able complete the network within the class period. As you can see in the photo below, we took a quick and dirty approach to our schedule – we lay out the courses in the correct “semester” then drew arrows all across the paper. The class period ended just as we were adding arrows from a common start activity (move into dorm) to all the courses without prerequisites and from the ending activities to a single merge activity (graduation).
After class I had the opportunity to create the same project network in Microsoft Project. As I expected, the network we made by hand was the same when recreated with MS Project. The software also produced a Gantt chart and clearly designated the critical path. The screenshot at the top of this page (and reproduced below) is the project network I produced after class.
As you can see, the network has one main critical path that continues throughout the diagram. The network is not sensitive, because there is only the one critical path. The critical path does split for one semester. The network, however, is still not overly sensitive. Failing one of the classes in red is guaranteed to delay graduation by at least one semester. Some of the classes in blue could theoretically be failed because they all have slack of at least one semester. This diagram is fairly simplistic, because it does not include any co-requisites or the fact that it is insane to take 7 classes at once. If co-requisite courses were added to either diagram the spaghetti maze would most certainly intensify. To signify the different types of relationships, dotted lines could be used. Also, some co-requisite classes could be combined into a single activity.
In this project I built a project network both by hand and with a computer. Using the computer was very easy, because once the activities and predecessor activities were typed up, the network was automatically created. Doing the project by hand, however, gave me a better understanding of how the entire network interacted. It is clear that each method has a place depending on the number of activities and the complexity of the network. I prefer using the computer program to create the project network, then studying the graphical printout of the network to identify critical tasks and the over all relationships running through the project.
Once the project network is created several clarifications and enhancements can be made. First, resource leveling can occur. This is where the resources required for each stage of the project are determined and adjustments made to minimize the fluctuations in resource requirements, such as labor. In the example of a civil engineering degree the number of credits per semester is the most reasonable “resource”. The requirements could state that no more than 6 classes can be taken during the first 3 semesters, and no more than 5 for the remaining time. The second task that could occur is planning for crashing the schedule. By shortening the length of the project, by accelerating activities along the critical path, indirect costs for the project will decrease and money can be saved. It is important to note that direct costs (overtime, more personnel, etc.) will increase, but usually the savings on indirect costs (rental of equipment, early completion bonuses, etc.) make completing a project early financially worthwhile. This concept is depicted in the chart below, taken from figure 10.15 from Construction Project Management.