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SFPE Example 1

Pathfinder 2011

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SFPE Example 1 This example attempts to reproduce example 1 in the SFPE Engineering Guide - Human Behavior in Fire

(SFPE, 2003). We determine the total movement time for a room containing 300 people. The room has a

travel distance of up to 200 feet to egress through two 32-inch doors that lead to two enclosed 44-inch

stairs (height and depth of tread of 7 inches and 11 inches, respectively) and down 50 feet of stairs to a

wide discharge at grade, Figure 1.

Figure 1: SFPE Example 1 geometry (not to scale)

Create Geometry To select English measurements:

1. On the View menu, click Units and select EN to display measurements using the English system.

To specify snap grid spacing:

1. On the View menu, click Edit Snap Grid....

2. In the Specify snap grid spacing menu, type 10.0. By default, length units will be in feet,

however, you can type a value followed by a unit (e.g.: "in" or "m") and the length will be

converted to feet.

3. Click OK.

To define the default floor height:

1. In the Floor Height box, type 30.0.

To create the room:

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1. In the View toolbar, click Top View ( ).

2. In the Tools toolbar, click Add a Rectangular Room ( ).

3. In the Z Plane box, type 30.0.

4. Click and drag to draw the room from point (0,0) to (200,30). In order to properly see the

geometry, it might be necessary to zoom out by rolling back the mouse wheel. The dimensions

of the room will be displayed below the 2D view as you drag the mouse, Figure 2. You can also

directly type the coordinates into the coordinate boxes.

5. In the Name box type Room.

Figure 2: Drawing the room

To create the landing:

1. In the Tools toolbar, click Add a Rectangular Room ( ).

2. In the Z Plane box, type 0.0 ft.

3. The left edge of the landing should be 40 ft to the right of the room. Click and drag to draw the

landing from point (240,0) to (250,30), Figure 3.

4. In the Name box type Landing.

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Figure 3: Drawing the landing

To add the first stairway:

1. In the Tools toolbar, click Create Stairs between two edges ( ).

2. In the Stair Width box, type 44.0 in.

3. In the Door 1 Width box, type 32.0 in. Door 1 is the door associated with the first click of the

mouse when creating stairs.

4. The Tread Rise is 7.0 in and the Tread Run is 11.0 in.

5. Position the cursor at X=200 and Y=20 ft, click and then click a second time on the left edge of

the landing. This will create the stair.

6. In the Name box type Stair Left.

To add the second stairway:

1. In the Tools toolbar, click Create Stairs between two edges ( ) .

2. In the Stair Width box, type 44.0 in.

3. In the Door 1 Width box, type 32.0 in.

4. The Tread Rise is 7.0 in and the Tread Run is 11.0 in.

5. Position the cursor at X=200 and Y=10 ft and click. Hold the SHIFT key to switch the location of

the stairs and then click the edge of the landing to create the stair.

6. In the Name box type Stair Right.

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Figure 4: Drawing the left stairs

To add the exit door:

1. In the Tools toolbar, click Add a New Door ( ).

2. Click and drag along the edge of the landing opposite the stairs to add a door to the entire width

of the landing.

3. In the Name box, type Exit.

Figure 5: Adding the exit door

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Add Occupants To add 300 randomly spaced occupants to the room:

1. Using the Selection tool, right-click to select the room.

2. Click Add Occupants... .

3. In the By Number box, type 300.

4. Click OK.

5. On the View toolbar, click Perspective View ( ).

6. On the View toolbar, click Reset All ( ).

To display occupants as people:

1. On the View menu, click Agents and select Show as People.

Your model should look similar to Figure 6.

Figure 6: Completed model with occupants in perspective view

Run Simulation To run the simulation:

1. Save your document to a new folder. Use the name sfpe1.pth.

2. On the toolbar, click Run Simulation ( ).

3. A summary report is provided in the analysis dialog. It provides FIRST IN and LAST OUT times for

each room and door. The TOTAL USE gives the maximum number of occupants either in a room

or in the door queue, Figure 7.

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Figure 7: Simulation summary data given on the run dialog (also saved in summary.txt)

View Results When the simulation is finished, the 3D Pathfinder results window will display.

To view results:

1. Click the Play button. This will display the occupants as cylinders with their direction indicated

by a triangle.

2. At any time click the Pause or Stop button. You can drag the time line to control the animation.

3. To view occupants as people, click the Stop button, on the Agents menu, click Show as People,

then click the Play button, Figure 7.8.

Detailed information for each room is provided in comma-separated value (CSV) files that can be

imported to a spreadsheet. The total time taken for all occupants to exit is 179.3 sec.

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Figure 8: Animated display of movement

Select SFPE Mode Pathfinder provides the option to select different simulation modes. By default, the occupants act as

agents with a steering behavior that seeks to reach a goal while avoiding other occupants and

boundaries. The SFPE movement mode is consistent with the assumptions used in the SFPE Engineering

Guide - Human Behavior in Fire (SFPE, 2003). Assumptions include:

1. The occupants move toward the exits using the shortest path

2. The maximum occupant speed is a function of room density

3. Occupants move independently and can occupy the same space as other occupants

4. Queues form at doors, with the flow rate through the door as specified by SFPE guidelines.

Because multiple occupants can occupy the same space, a queue may appear as a single

occupant.

To select the SFPE mode:

1. On the Simulation menu, click Simulation Parameters....

2. Click the Behavior tab.

3. In the Behavior Mode box, select SFPE.

4. In the Door Boundary Layer box, type 6 in.

5. Click OK.

Before running the analysis, save the model using the name sfpe1_sfpe_mode.pth. The total time

for all occupants to exit is 242 sec.

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Compare Results to SFPE Calculation The SFPE solution to this problem is given below.

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The Pathfinder solution gives the time to exit the stairs as 242 sec, compared to the SFPE solution of

241.6 sec (4.027 minutes), calculated without the round-off used in the example explanation.

Adding Collision Avoidance to the SFPE Mode The SFPE mode does not prevent multiple occupants from occupying the same space. A collision

handling option can be added to the SFPE calculation. Flow rates through doors and walking speeds are

still calculated using the SFPE To run with this movement option:

1. Open the sfpe1_sfpe_mode.pth model created above. On the File menu, click Save As...

and give the name as sfpe1_collision.pth.

2. On the Simulation menu, click Simulation Parameters....

3. Click the Behavior tab.

4. In the Behavior Mode box select SFPE.

5. Click to select Add Basic Collisions.

6. Click OK to close the Simulation Parameters dialog.

7. Run the simulation.

In the new solution, the time to exit the stairs is 242 sec. These times are similar to the standard SFPE

solution, but the appearance of the solution is improved, since the occupants form queues at the doors.

Figure 9: SFPE mode with added collision handling. This uses SFPE rules to calculate the flows, but improves the display of the results.

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References [SFPE, 2003] Engineering Guide - Human Behavior in Fire. June, 2003. Society of Fire Protection

Engineers. 7315 Wisconsin Avenue, Suite 620E Bethesda Maryland USA 1-301-718-2910.