SPECIFICATION FOR THE DESIGN OF - Transcon Steel
SPECIFICATION FOR THE DESIGN OF - Transcon Steel
SPECIFICATION FOR THE DESIGN OF - Transcon Steel
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Commentary on the Prescriptive Method for One and Two Family Dwellings - 2004 41<br />
D1.4 Web Crippling Capacity<br />
Although floor joists are required to have web stiffeners at both ends and at<br />
concentrated load locations (hence, there is no need to compute the web crippling strength),<br />
however, the web crippling strength of the subject floor joist is calculated below to illustrate<br />
the use of the web crippling equations.<br />
Refer to Section C3.4.1 of the Specification, for webs with no holes. The equations given in<br />
Table C3.4-1 of the Specification are applicable to sections with N/t ≤ 210, N/h ≤ 3.5 and R/t ≤<br />
7. For the given 1000S162-54 joist section, these provisions are met.<br />
The length of bearing (N) is assumed to be a minimum of 1.5”.<br />
Use equation C3.4-1-1 for single webs, stiffened flanges:<br />
P n = t 2 k C 1 C 4 C 9 C θ [331 - 0.61(h/t)][1 + 0.01(N/t)]<br />
k = 894F y /E = 894(33)/29500 = 1.0<br />
(Note F ya cannot be used for this section)<br />
C 1 = 1.22 - 0.22k<br />
k = 894F y /E = 894(33)/29,500) = 1.0<br />
C 4 = 1.15 - 0.15R/t = 0.866<br />
C 9 = 1.0<br />
C θ = 0.7 + 0.3(θ/90) 2 = 1.0<br />
P a = (0.0566) 2 (1.00)(1.00)(0.866)(1.0)[331 - 0.61(170.87)][1 + 0.01(1.5/0.0566)]<br />
P n = 0.796 kips = 796 lbs<br />
Φ v P n = 0.75(796) = 597 lbs<br />
(Eq. C3.4.1-1)<br />
(Eq. C3.4.1-21)<br />
(Eq. C3.4.1-11)<br />
(Eq. C3.4.1-21)<br />
(Eq. C3.4.1-12)<br />
(Eq. C3.4.1-19)<br />
This capacity should be reduced to account for the presence of holes in the web in<br />
accordance with the Specification. The reduced capacity is: Φ v P n = 597 lbs (assuming the value<br />
for “X” is greater than or equal to 9”, therefore, R c = 1.0).<br />
w f = 152 plf<br />
Φ v P n = L max w/2 L = 595(2)/152 = 7.83’ = 7’-10”<br />
The resulting capacity of 597 lbs is less than the factored crippling load for spans greater<br />
than 7’-10”; therefore, web stiffeners are required.<br />
The maximum allowable joist span is the minimum span calculated based on shear,<br />
moment, and deflection. The resulting span is 15’-11” (controlled by live load deflection).<br />
This result confirms the value published in the Prescriptive Method, Table D3-1.
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