Managing Resources Through Allocation and Leveling via Manual and Computer Applications

Introduction

The success of a construction schedule is determined by its timely completion. Through a carefully planned sequence, the schedule coordinates the assembly of individual work activities by dictating start and completion dates. The total number of days it takes to build a project is controlled by the durations of the scheduled work activities. The duration of each work activity is equal to the quantity of work divided by the production rate. Shortages of essential resources can affect the performance and completion of scheduled work activities by lowering the planned production rate and thereby extending the planned duration of work beyond the anticipated completion date (Callahan, 1992). Ignoring constraints placed on the schedule by the limited supply of resources lessens the effectiveness of using the construction schedule as a management tool (Glavinich, 1994). Therefore, the resource requirements for each activity should be evaluated before a schedule is put into action. Resource allocation, also known as resource loading, is the process that breaks down work activities into the types and quantities of labor, equipment, and materials needed to perform the work. As a result, one is able to determine the anticipated resource needs, and plan accordingly. Resource leveling takes the management of resources one step further by analyzing the resource needs of the entire construction project and attempting to minimize the problems associated with insufficient quantities and/or fluctuations in resource demand on a day-to-day basis. While computer-based programs may be used to allocate and level resources within the schedule, the authors feel a basic knowledge of the allocation/leveling process is important. The applications of both resource allocation and leveling are explained in this paper through the use of a scheduling, example problem.

Resource Allocation

Work performed on construction job sites requires the utilization of labor, equipment, and materials resources. As previously stated, shortages in the quantity or availability of any essential resources can affect the performance and completion of scheduled work. Therefore, the resource requirements for each activity should be evaluated before a schedule is put into action. By allocating the labor, equipment, and materials required to perform each individual task on the schedule, one is able to pre-plan the anticipated resource needs for each workday of the project before the schedule is put into action. This total resource requirement is then compared with the quantity (supply) on-hand. If the supply on-hand exceeds the requirement, then the schedule can be worked as planned. If it is found that the demand exceeds supply, then steps need to be taken to ensure that the proper amount of resource will be on hand on the date needed. It should be noted that the Resource Allocation process only determines whether or not there is a problem when comparing resource supply and demand. It will not state the course of action needed to correct the problem. 

The example problem used to illustrate Resource Allocation is shown in Figure 1. The logic diagram shows the sequence of construction and is reflected in the attached bar chart. The resource to be analyzed for the example problem will be Workers.

The hypothetical construction company responsible for the project illustrated in Figure 1 employs 6 workers within the company, and wishes to use 4 of these workers on our example project. Therefore, the normal number of Workers will be equal to four, and the maximum number that could possibly be available will be equal to 6 workers. Note that the number of workers required for each workday for each individual work activity is shown in the Workers column on the bar chart in Figure 1.

In Figure 2, using the same information found in Figure 1, these workers are allocated to the activity bars representing each activity. The total of each day’s need for workers is shown in the row entitled “Total” in the lower part of the bar chart.

Note that the total number of workers required for Days 1 through 3 requires seven workers per day. This demand exceeds the maximum number of workers available in the company, so this schedule cannot be worked with the amount of resources on-hand. By having taken the action of allocating the resources into the schedule prior to start, one was able to determine that the demand would exceed the supply on-hand. Implementing this schedule with only the six workers that are employed will result in productivity lower than anticipated. Delays will be experienced unless additional resources (workers) are made available through either hiring extra workers or changing the sequence of work activities. Without prior allocation of resources, this fact would not have been discovered until a delay was caused by a resulting lower-than-anticipated productivity. The worker resource requirement for the schedule shown in Figure 2 is illustrated by the histogram in Figure 3.

Since it is found in the example problem that the demand exceeds supply, one now knows that an action must be taken to ensure that the proper amount of resource will be on hand on the date needed. Though the resource allocation process will not dictate the course of action that is needed to correct the problem, it is always better to have discovered a potential problem before work is in progress.

Resource Leveling

The fluctuations of resource usage of labor, equipment, or materials can be very expensive. The expense that results from fluctuations in labor supply comes in the form of continuous training and lay-off of new employees, or in the mobilization and demobilization of construction equipment (Glavinich 201). Leveling the demand for resources helps minimize the large day-to-day fluctuations in the number of resources needed. Note in Figure 2 the fluctuation of workers needed for Days 3 through 5 in the example schedule. Seven workers are needed on Day 3, while only four workers are required on Day 4. Therefore, if the current schedule is used as illustrated in Figure 2, then three workers would either have to be used on other projects or laid-off. On Day 5, one of the workers sent away on Day 4 would have to be sent back to the example project.

To manipulate the daily resource requirements, resource leveling is now implemented.  Resource leveling involves the delay of non-critical activities within their Total Float Limits to manipulate the daily resource requirements. The Total Float of each activity is the maximum amount of time (days in this case) that the activity can be delayed without causing a delay to the project’s completion date. Critical activities are not considered for delay due to the fact that any delay to work activities on the critical path will delay the project completion date. The manual method of leveling work activities in the schedule can be performed by either formula-based or trial-and-error methods. To simplify the explanation process in this paper, the trial-and-error method of arbitrarily delaying the start of Activity B, a non-critical activity, by seven days, will be used. The results of this arbitrary delay are presented in Figure 4.

When Activity B is delayed, its succeeding activity (Activity E) is also affected. Also note that the Project Completion date is not affected by the delay in Activity B. The resulting Resource Histogram showing the results from this delay is shown in Figure 5.

Compare the histogram shown in Figure 3 with the leveled histogram shown in Figure 5. By redistributing resources (resource leveling) among the workdays of the leveled schedule, the fluctuations in demand are lessened. Notice that the total resource requirements for both the before and after schedules (Figures 2 and 4) are equal to 56 units. This proves that the resources were redistributed throughout the schedule. Therefore, no more or no less Worker resources were spent to create this histogram. In fact, the histogram in Figure 5 also illustrates that the hypothetical construction company used in the example may be able to complete the work by using its current workers in its labor force.

Comparison of Resource Management in Software Programs

Microsoft Project and Primavera Project Planner are two popular scheduling software programs used in the construction industry. Both programs allow the user to allocate and level the type and quantity of resources required for each activity on the schedule. The steps required to input and calculate the resource information, however, differ slightly in each program. The same example schedule used previously in this paper will be used to demonstrate the resource allocation/leveling processes in both Microsoft Project and Primavera Project Planner.

Resource Allocation/Leveling in Microsoft Project

To allocate the resources using Microsoft Project, the following steps are taken:

Once the schedule is created in Microsoft Project, use the computer mouse to select an activity by clicking on an Activity in the Task Name field.

Then click on the Assign Resources icon located on the toolbar shown at the top of the computer screen (see Figure 6).

Next, the Units field of the Assign Resources window is filled in.  The number of workers required for the activities is based on percentages (one worker = 100%, two workers = 200%, etc.) Based on our example schedule, four workers are required to perform the work for Activity A. Therefore, in Microsoft Project, 400% is used in the Units field of the Assign Resources window.

After the resource is created, the maximum quantity of the resource available is set by clicking on the Resource Sheet icon and placing its value in the Maximum Units column (see Figure 7 below).

Note that the option to set normal limits is not available in Microsoft Project. Once the resources have been allocated and their respective maximum values have been input, the resource usage histogram may be viewed by clicking on the Resource Graph icon.

The histogram shown in Figure 8 illustrates the resource usage/requirements before any leveling is performed. Note that the histogram shown in Figure 8 reflects the same information found in the histogram found in Figure 3. Since the worker resource is over-allocated during the first three days of the project, leveling will be used to minimize the fluctuations in resource needs.

To level the resources in the Microsoft Project schedule, click on the Tools menu and select the Resource Leveling option. The results shown in Figure 9 were obtained by applying an Automatic Leveling of the entire project.

Resource Allocation/Leveling in Primavera Project Planner

To allocate resources using Primavera Project Planner, the following steps are taken:

Before resources can be allocated to each activity in a Primavera Project Planner schedule, the resource(s) must be created in the Resource Dictionary. Click on the Data menu (located at the top of the toolbar) and select the Resources option (see Figure 10). Input a four-character abbreviation in the Resource column and its explanation in the Description column. Input the normal and maximum levels in the Limits section of the Resources Window. Hit the Close button when input is complete.

Resources are allocated to the appropriate activities by way of the Activity Form icon (see Figure 11).

Select the Resource Button (abbreviated as “Res”) in the Activity Form located on the bottom half of the screen (see Figure 11). Highlight an activity of the schedule and input the type of resource(s) needed to perform the work by clicking in the Resource field. Enter the quantity of resources needed in the Units Per Day row (see Figure 12).

After allocating the resources to each activity on the schedule, the Resource Profile (Histogram) is generated by clicking on the Resource/Cost Profile icon (see Figure 11). Next, the Resource Profile Display Options should be set as follows: Time Interval=Days, Histogram Option is “checked,” and the options Draw Limits and Emphasize Overload with Color are “checked” (see Figure 13).

The histogram for the example schedule is shown in Figure 14. Note that this histogram matches the previous resource histograms.

To level the resources using Primavera Project Planner, click the Level icon (see Figure 11) to level the schedule.

The histogram shown in Figure 15 reflects forward, time-constrained leveling. Again, note that it agrees with the previous leveled histograms shown in this paper.

Both Microsoft Project and Primavera Project Planner provided the same values when the example schedule was allocated and leveled through the use of the respective software programs. Therefore, since each program will provide information to help with the management of resources, deciding which of these computer-scheduling programs to use is a matter of personal preference. However, it should be noted that algorithms used by scheduling software might not offer the best solution to a resource-leveling problem (Glavinich, 1994). The individual manager should analyze the solution presented by the computer to determine if it is realistic and meets the needs of the company. If the solution is deemed unsuitable, one only needs to reset back to the original schedule by hitting the Schedule icon in Primavera Project Planner or by selecting the Clear Leveling option in Microsoft Project.

Conclusion

The success of a construction schedule is determined by its timely completion. The impact of the limited resource supplies and the corresponding effect on the project’s completion date should be analyzed prior to the implementation of the schedule. This action is important due to the fact that the duration of each work activity is dependent on the availability of resources. Allocating resources into the schedule is necessary to determine if there is a sufficient supply of resources on hand to perform the work as planned. In addition to the quantity of resources available, problems may exist in the daily fluctuations of resource demand. Therefore, resource leveling is used to minimize the day-to-day fluctuations. While the manual method of allocating and leveling resources is discussed in this paper, it is the opinion of the authors that resource management of today’s fast-paced and complex schedules is only practicable through the use of computerized scheduling programs. However, one must analyze the practicability of the solution presented by the software before it is implemented. The example problem shown in this paper is intended to illustrate the importance of the resource allocation/leveling process and provide the reader with instructions for using either Microsoft Project or Primavera Project Planner.

References

Callahan, M. T., Quackenbush, D. G., & Rowings, J. E.  (1992).  Construction Project Scheduling.  New York: McGraw-Hill, Inc.

Glavinich, T. E., & Stella, P. J.  (1994).  Construction Planning and Scheduling.  Washington, DC: AGC of America.

Primavera Project Planner Version 3.0 Reference Manual.  (1993).  Bala Cynwyd, PA: Primavera Systems, Inc.

Step By Step Microsoft Project 98.  (1997).  Redmond WA: Microsoft Press; 1997.