AISCAISC 360-22
Formulas

Formulas: Composite Steel-Concrete Columns

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Equation A-4-31

The fire-resistance rating, RR, of hollow structural section (HSS) columns filled with unreinforced normal weight concrete, steel-fiber-reinforced normal weight concrete, or bar-reinforced normal weight concrete is permitted to be determined in accordance with Equation A-4-31 or A-4-31M:

R=0.58a(fc′+2.9)D2(DC)0.5Lc−3.28R=\frac{0.58 a\left(f_{c}^{\prime}+2.9\right) D^{2}\left(\frac{D}{C}\right)^{0.5}}{L_{c}-3.28}

Equation A-4-31M

R=a(fc′+20)D2(DC)0.560(Lc−1000)R=\frac{a\left(f_{c}^{\prime}+20\right) D^{2}\left(\frac{D}{C}\right)^{0.5}}{60\left(L_{c}-1000\right)}

where

  • C=C= compressive force due to unfactored dead load and live load, kips (kN)
  • D=D= outside diameter for circular columns, in. (mm)
  • = outside dimension for square columns, in. (mm)
  • = least outside dimension for rectangular columns, in. (mm)
  • Lc=L_{c}= column effective length, ft (mm)
  • R=R= fire-resistance rating, hr
  • a=a= constant determined from Table A-4.3.4
  • fc′=28f_{c}^{\prime}=28-day compressive strength of concrete, ksi (MPa)

Found in

Formulas: Steel Columns

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Equation A-4-31Equation A-4-31MFound in