PE Problem #4

6/7/2019

A stair is 59 inches wide, with a handrail on one side with a centerline of 1.5 inches from the edge of the stair. The other side of the stair is a wall. For the purposes of calculating a specific flow, what is the effective width of the stair?
a. 47 in.
b. 48 in.
c. 53 in.
d. 59 in.

Solution | Posted 06/10/19

7 Comments

Ryan

6/7/2019 07:19:21 am

47 in, A)

From Figure 4.2.4 and Table 4.2.4 of the NFPA Handbook, subtracting 6" on each side of the stair tread for the wall and edge of tread equals 47". The second paragraph on Page 4-59 states that only handrails that protrude more than 2.5" need to be considered since the boundary layer for handrails in 3.5" vs 6" for the edge of tread boundary layer. The smaller effective width is utilized.

Also discussed on Pages 2122-2124 of the SFPE Handbook

Amr

6/7/2019 10:41:35 am

b) 48 in.

SFPE Handbook Fig. 59.5 to calculate the first side with handrail 3.5 in. + 1.5 in. = 5 in.

SFPE Handbook Table 59.1 to calculate the other side with wall only = 6 in.

the effective width will be = 59 in. - (5 in. + 6 in.) = 48 in.

6/7/2019 10:48:08 am

a. 47 inch

FPH Table 4.2.4 Boundary layer widths
6 inches for walls
3.5 inches for handrails, however 3.5 in + 1.5 in = 5 in. So use 6 in for the wall with the handrail, as well.

59 in - (2) * 6 in = 47 in

6/7/2019 11:44:54 am

a. 47 inches

Effective width for flow calc from SFPE Handbook, 5th ed. Table 59.1

since 1.5" + 3.5" = 5" < 6"

both sides are considered to have a boundary layer of 6"

Brenton

6/7/2019 10:23:24 pm

A. 47”.

Boundary widths (FPH table 4.2.4)
Walls - 6”
Handrail - 3.5”
Handrail is 1.5” from edge of stair: 1.5 + 3.5 = 5”.
The greater width is the edge of stair tread (6”), so effective width is 59 - 6 - 6 = 47”.

6/8/2019 07:10:00 am

A) 47 inch

9/6/2019 02:39:11 am

a. P4-58, The effective width of any portion of an exit route is the clear width of that portion of an exit route less the SUM OF BUNDARY LAYERS for STAIR and WALL FROM TABLE 4.2.4.

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