Assessing and Optimizing with Area Occupancy Limit (or Area Density Constraint, Work Density Constraint, Maximum Space Utilization)
Challenge:
Accounting for how many people or pieces of equipment can fit into a specific onsite area is a complex task in construction scheduling. Schedulers must ensure resources are considered, then manually reshuffle activities and re-tie logic to accommodate area density constraints. Recognizing and incorporating these constraints is crucial for maintaining a safe, efficient, and productive work environment. Moreover, it ensures a more realistic and reliable schedule that reflects the true dynamics of the work environment.
Why Area Density Constraints Matter:
- Safety Hazards: Overcrowded work areas significantly increase the risk of accidents and injuries. When too many workers and equipment are concentrated in a limited space, maintaining safe working conditions becomes challenging.
- Reduced Productivity: High-density work areas lead to inefficiencies and delays. Workers navigating through congested spaces experience slower progress and increased frustration.
- Quality Compromises: Overcrowded work areas compromise the quality of work. Workers may rush to complete tasks in confined spaces, resulting in errors and rework.
Solution:
ALICE can tackle this challenge by incorporating an area density constraint into your schedule. A capacity limit can be set for the number of people or equipment in an area of your project, and the schedule output will account for this constraint while also optimizing your project based on your objectives.
The most effective way to model area density is through the Materials Resource functionality. We will explain this in more detail shortly.
Here is an example showcasing how ALICE takes into account area occupancy constraints:
The water main project is broken out into three sections: S1, S2, and S3. In the current schedule (baseline), the number of people working in each area are as follows:
Baseline Occupancy Density:
- Area S1: 13 people peak
- Area S2: 15 people peak
- Area S3: 17 people peak
Here is the occupancy density histogram, organized by area, showcasing the number of people over time.
Figure 1: Baseline: Area Density Histogram at Water Pipe Sections S1, S2, S3 (# of People at Each Section)
Focusing on August 30th, 2027, for Area S3, the peak number of people working in that area is 17, as shown in both the area density histogram view and the Gantt view.
Figure 2: Baseline: Area Density Histogram at Water Pipe Section S3 (# of People at Section S3) - 17 People Peak
Figure 3: Baseline Gantt View Showcasing Peak Density at Water Pipe Section S3 - 17 People Peak
However, to adhere to safety guidelines, I want to cap the maximum number of people to 10 per area. By running a scenario in ALICE with this limitation, ALICE generates a new optimal schedule that respects this added constraint.
Here are the new constraints in ALICE:
Figure 4: New constraint configurations on the Explore Page where the quantity is capped at 10 people maximum per area.
And here is the resulting occupancy density histogram, organized by area.
Figure 5: Optimized with Added Constraint of 10 People per Area (Area Density Constraint Added at Water Pipe Sections S1, S2, S3)
Resulting Occupancy Density Histogram:
- Area S1: 10 people peak
- Area S2: 10 people peak
- Area S3: 10 people peak
Taking a closer look at Area S3 again, the new schedule reflects the capped limit, ensuring a safer work environment.
Figure 6: Optimized with Added Constraint of 10 People per Area (Area Density Constraint Added at Water Pipe Section S3)
How to Impact the Bottom Line:
Protect Your Margins: Create more realistic schedules that reduce unexpected delays and disruptions by taking into account area density constraints that may impact site productivity, work quality, and safety.
How ALICE is Different from Other Tools:
ALICE excels by incorporating personnel and equipment density constraints per area, while simultaneously maintaining all other provided constraints. It considers every variable defined in your schedule (the parameterization aspect), and through its powerful optimization engine, generates the most optimal schedules for your review.
Example Use Case:
As an Industrial Contractor working on a power plant, it is crucial to consider the number of people that can safely fit into each work zone. This not only ensures adherence to safety requirements but also maximizes work output by efficiently utilizing available space.
How to Optimize your Schedule by Adding an Area Occupancy Limit (Area Density Constraint):
Step 1:
On the Plan page, open the Resources tab and create the work areas that you want to define in your schedule.
- Create new Materials Resources for each of the work areas
- Set all of the material resources to type Reusable
- Set Qty Avail. to ∞ (to indicate unlimited amount for now)
- Set $/Unit to 0 (so that the cost of this material does not add unnecessary costs to your project)
Note: We use the Materials Resource as a way to set up area density constraints.
Step 2:
On the Plan page, assign your activities to each work area using the material resource created.
Figure 7: How to configure assigning an occupancy area density (based on labor) to each activity.
- Set the action to Requires
- In the Amount column, fixed numbers or formulas are supported. In the example here, num_crews is used to indicate the total number of people assigned to that activity
- If the number of people in the crew is not 1, you may want to use num_crew_size instead
- Note: If the activity has a Crew Range assigned, then the material quantity (or amount assigned to your work area) will vary accordingly.
Step 3:
Repeat Step 2 to apply the work areas to all of the activities in the schedule where the area density constraint should be taken into consideration.
In the example here, you can see activity “Mobilize Drill” is located in area S2 and takes 3 people total.
Figure 8: Example where the setup is complete on the Plan page; all activities have area densities assigned based on the number of crews.
Step 4:
Run a scenario using Qty. Avail. = Max to see how many people are working in each area in your current schedule.
Figure 9: Configuration on the Explore Page where the area density is unlimited (unlimited number of people per area).
Step 5:
Run another scenario using a different density constraint (e.g. Density: S3 = 10).
Step 6:
Compare the solutions. Select the best optimization sequence and export the schedule to your desired format.
Figure 10: High level comparison on the Explore page for the two scenarios (unlimited # of people per area vs. 10 people capped per area).
Note: You can assign an equipment occupancy limit in a similar way. Instead of using num_crews or num_crew_size as the formula dictating the number of people in the area, use the equipment variable to dictate the number of equipment in the area. In this example, S3 area is limited by the number of drill rigs:
Figure 11: How to configure assigning an occupancy area density (based on equipment) to each activity.
How to Optimize your Schedule by Adding a Workforce Limit (and How this Differs from Area Occupancy Limit):
Instead of providing a constraint for the number of people per area, it is also possible to provide an overall workforce limit. By applying a workforce limit, ALICE will not exceed the total number of people at any given time throughout the entire duration of the project.
ALICE takes into account the # Prs./Crew information from the Crews tab in your project set up. Therefore, the workforce limit is based on the num_crews * num_crew_size in the Crew assignment, while area occupancy limit is based on the Materials assignment.
From the Plan page, you can apply the Workforce limit from the Resources tab:
Figure 12: Setting up the Workforce limit on the Plan page under Resources.
When exploring new scenarios, you can adjust the Workforce limit under Create New Scenario, Crews tab:
Figure 13: Providing a Workforce limit on the Explore page when running a new scenario.