Formulas: Concrete Floor Slabs on Steel Deck

Equation A-4-33

For composite concrete floor slabs on trapezoidal steel decking wherein the upper width of the deck rib is equal to or greater than its bottom rib width, the fire-resistance rating, based on the thermal insulation criterion for the unexposed surface temperature, is permitted to be calculated using the following equation:

\begin{aligned} R & =a_{0}+a_{1} h_{1}+a_{2} h_{2}+a_{3} l_{2}+a_{4} l_{3}+a_{5} m+a_{6} h_{1}^{2} \\ & +a_{7} h_{1} h_{2}+a_{8} h_{1} l_{2}+a_{9} h_{1} l_{3}+a_{10} h_{1} m+a_{11} h_{2} l_{2} \\ & +a_{12} h_{2} l_{3}+a_{13} h_{2} m+a_{14} l_{2} l_{3}+a_{15} l_{2} m+a_{16} l_{3} m \end{aligned}

where

$R=$ fire-resistance rating, min
$h_{1}=$ concrete slab thickness above steel deck, in. (mm)
$h_{2}=$ depth of steel deck, in. (mm)
$l_{1}=$ largest upper width of deck rib, in. (mm)
$l_{2}=$ bottom width of deck rib, in. (mm)
$l_{3}=$ width of deck upper flange, in (mm)
$m=$ moisture content of the concrete slab, %. Range of applicability is between $0 \%$ (0.0) and $10 \%$ (0.1).

Formula 2

User Note: If moisture content values are not available, $m=4 \%$ can be used for normal weight concrete, and $m=5 \%$ can be used for lightweight concrete, consistent with Annex D of Eurocode 4.

m=4 \%

Formula 3

m=5 \%

Formula 4

Dry conditions ( $m=0 \%$ ) will yield the most conservative fire-resistance rating.

m=0 \%

Found in

DESIGN BY QUALIFICATION TESTING