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Project Control: Developing the As-Planned S-Curves

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1 Project Control: Developing the As-Planned S-Curves
Part #2 March 31, 2017 Hide/Unhide Exercises Background: During the Project Development Cycle there is a Planning Phase and a Construction Phase. Part #2 of the module covers the basics of how to develop the As-Planned S-Curves during the planning phase. Part #2 covers the Development of the As-Built S-Curves during the construction phase. Part #3 Covers how to determine Job Status during the construction phase using both sets of curves. Part #3 also covers interpretation of the results. Reading Assignment: Halpin and Woodhead, Chapters 2, 6, 12, and 14. This Part should take minutes to cover in detail, depending upon the level of experience of the students. This timing assumes that students are somewhat familiar with the estimating and scheduling process. You could shorten the time by leaving ou the exercises.

2 Purpose Illustrate how to develop a set of As- Planned S-Curves from scheduling information and estimates developed sometime before actual construction operations begin. Review the conceptual design estimating process to the extent necessary to set the context. These constitute the teaching objectives.

3 Learning Objectives Be able to construct an as-planned schedule of work and cost versus elapsed time from a typical (but simplified) construction project Gantt Chart. Be able to plot and identify the as Planned S-Curves best representing these schedules. These Learning Objectives could make excellent pop questions. However, I usually ask Exam questions around the complete set and not the As-Planned set.

4 Who Develops the As Planned Gantt Chart? And When?
It depends upon what part of the process is in question. We are going to assume that the Gantt Chart is developed by the Contractor to plan construction operations. We are going to assume that the schedule data are generated sometime before the onset of actual field operations. Theoretically, S-Curves can be used to control the planning phase as well as the construction phase of the process. As a matter of practice it is rarely done. That is not to say that on mega projects it would not be a good idea.

5 Example Construction Project
The project is to reconstruct 2-miles of park access road conforming to Texas FM-Road standards. This involves the following tasks: Mobilization – Equipment, office set up, etc. Sub-base preparation – hauling, grading and compaction, redo of some culverts, etc. Base course construction – hauling, grading and compaction. Wearing Course construction – shoot and chip Demobilization – Clean up, equipment, office, etc. I often use this example project in the design of hour exams and finals.

6 Class Discussion Exercise #2.1 on Construction Methods.
Ask Selected Individuals or Pairs to answer the following: What is Base Material and what is its purpose in the design of the road? How is the Base built? What is “shoot and chip?” What is Pea Gravel? What is the design profile of a FM Road? In-class surveys have shown that very few of today’s students have any degree of familiarity with construction of any type. They will be unfamiliar with most of these common road construction terms. So, it will be necessary to go over them in some detail. Base Material: In Central Texas it is generally crushed and graded limestone material from one of the Quarries along the Balcones Escarpment. It is generally put on top of the sub-base in 12-inch lifts and compacted to optimum density using a variety of compaction equipment. It is the load bearing structure. Shoot and Chip: Texas practice is to shoot a thin asphalt layer on top of the compacted base course and then spread a layer of chips (pea gravel) over that. This is the wearing surface. Pea Gravel: Is a manufactured, gap graded (.25” to .50”) gravel with most of the fines removed. It can be hard limestone or river gravel. Limestone is preferred because of polishing. Design Profile: The design life of a rural FM Road in Texas is normally 4-years. At that time a shoot and chip seal coat is applied after any major break-up of the base material is repaired. At the end of 7-years the pavement condition is assessed. And the road is resealed or rebuilt as required. Light traffic roads in West Texas seldom need rebuilding. Roads in the fat-clay regions of central and east Texas require constant maintenance because of failure of the sub-base. This causes structural failure of the base course, etc. It would cost $-billions to build FM-Roads to any other design profile. High volume roads are built to higher standards.

7 Project Task Duration and Cost Data
Assume: All labor, material and equipment cost estimates are available from the estimating process. Maximum Task overlap with a 1-day minimum delay on an early start schedule. This is an example of sequential tasking. The base can not be applied until the sub-base is prepared. A section of road can not be paved until the base is prepared. Some over-lap can be tolerated. For example, the base usually cures a day before it is paved. To avoid start and stop operations (they are expensive) the contractor will wait until the base is almost complete before starting paving operations.

8 Assumed Estimating Process
The entire project is broken into Work Packages (work breakdown structure): build base, shoot and chip, etc. Estimated unit quantities for each work package are calculated from the plans and specifications at an appropriate level of detail. The corresponding unit prices and productivity rates are obtained from historical data – We will use the R. S. Means manual in this class. Work Package (or Task or Activity) durations and costs are derived from the historical data as applied to the estimates. These data serve as inputs to the scheduling process which result in Bar-Charts similar to the one on the next slide. Section 12.9 in Halpin has some good examples of breaking a project into work packages. In is good practice to use the Means Manual as a guide.

9 Class Exercise 2.2 As individuals describe the crew (equipment and personnel) configuration necessary to construct the base course. As Pairs agree upon the configuration. As a Team, estimate the hourly cost rate. The actual answer is not as important as getting the students to think about the process hauling the base material to the site, grading and shaping the dumped material, and then compacting it to proper density.

10 Example Gantt Chart with Related S-Curve % Data
There is a lot of busy work on this slide. The schedule information is on the top. This typically comes from any planning software like Primavera or Project. Resource allocation and costing can also result from running one of the industry standard software suites. This is an example using Excel to display the required operations. The Bar Chart shows which tasks are active on which days and the daily cost rates. The cost per day can be computed directly. The %/day follows. The total work per day is not easy to obtain. For planning purposes, you could assume that work is a function of cost as modified by some weighting factor. In this case we assumed that they were independent. Simplifying assumptions: All work is equally weighted where 1 day equals 1 unit of work. Daily work accomplished is NOT a function of daily cost.

11 Class Exercise #2.3 As Individuals, compute the number of cubic yards of base material required to build 2-miles of FM Road base, 24-feet wide, and 1-foot thick? As Pairs, compare answers and then compute the linear feet of daily progress, if you can build 2,700 sq-yds of base per day? In construction, volumes of bulk materials are measured in cubic yards, areas in square yards or square feet, linear (or running) measurements are in feet and miles. This is a good opportunity to make sure everyone remembers the conversions and how to use them. In the estimating module you actually use all of this but since that occurs prior to construction this is simply a review.

12 What Does all this Imply?
The relationship between time and cost and time and work. For example, at the end of day 8 you plan to have completed 50% of the Work and to have spent 47% of the Budget. These data were taken from the bottom of the Bar-Chart slide and displayed vertically. If we assume that cost and work are only loosely related, you should not be surprised to see cost and work only loosely related.

13 Corresponding As-Planned S-Curves
Note: The relationship between the scales. There is a reason – to make room for the As-Built S-Curves This shows the correct way to plot the data from the table in the previous slide. At this point there is not much to say about the curves. The different scales are important; so, make an issue of it. It will become obvious when we plot the As-Built Curves in the next Part.

14 Exercise #2.4 Individually, using engineering paper, plot the S-Curves for these data, label the axes, the curves, and the plot. Turn in your work before you leave. You will need to furnish a some graph paper for this exercise. Engineering paper will do. DO NOT hand out a template. Have the students plot from scratch. This does not make a good Exam problem.

15 Module Assessment Question
If you had to ask a question about this topic, what would it be?

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