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// CODE SNIPPET

722.5.1.4 Concrete-Protected Columns

Los Angeles Building Code > 7 Fire and Smoke Protection Features > 722 Calculated Fire Resistance > 722.5 Steel Assemblies > 722.5.1 Structural Steel Columns > 722.5.1.4 Concrete-Protected Columns
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The fire resistance of structural steel columns protected with concrete, as illustrated in Figure 722.5.1(6) (a) and (b), shall be permitted to be determined from the following expression:

(Equation 7-14)

where:

Ro=10 (W/D)0.7 + 17 (h1.6/kc0.2) × [1 + 26 {H/pccch (L + h)}0.8]

As used in these expressions:

R = Fire endurance at equilibrium moisture conditions (minutes).

Ro = Fire endurance at zero moisture content (minutes).

m = Equilibrium moisture content of the concrete by volume (percent).

W = Average weight of the structural steel column (pounds per linear foot).

D = Heated perimeter of the structural steel column (inches).

h = Thickness of the concrete cover (inches).

kc = Ambient temperature thermal conductivity of the concrete (Btu/hr ft °F).

H = Ambient temperature thermal capacity of the steel column = 0.11W (Btu/ ft °F).

pc = Concrete density (pounds per cubic foot).

cc = Ambient temperature specific heat of concrete (Btu/lb °F).

L = Interior dimension of one side of a square concrete box protection (inches).

722.5.1.4.1 Reentrant Space Filled

For wide-flange structural steel columns completely encased in concrete with all reentrant spaces filled [Figure 722.5.1(6)(c)], the thermal capacity of the concrete within the reentrant spaces shall be permitted to be added to the thermal capacity of the steel column, as follows:

(Equation 7-15)

where:

bf=Flange width of the structural steel column (inches).
d=Depth of the structural steel column (inches).
As=Cross-sectional area of the steel column (square inches).

722.5.1.4.2 Concrete Properties Unknown

If specific data on the properties of concrete are not available, the values given in Table 722.5.1(2) are permitted.

722.5.1.4.3 Minimum Concrete Cover

For structural steel column encased in concrete with all reentrant spaces filled, Figure 722.5.1(6)(c) and Tables 722.5.1(7) and 722.5.1(8) indicate the thickness of concrete cover required for various fire-resistance ratings for typical wide-flange sections. The thicknesses of concrete indicated in these tables also apply to structural steel columns larger than those listed.

722.5.1.4.4 Minimum Precast Concrete Cover

For structural steel columns protected with precast concrete column covers as shown in Figure 722.5.1(6)(a), Tables 722.5.1(9) and 722.5.1(10) indicate the thickness of the column covers required for various fire-resistance ratings for typical wide-flange shapes. The thicknesses of concrete given in these tables also apply to structural steel columns larger than those listed.

722.5.1.4.5 Masonry Protection

The fire resistance of structural steel columns protected with concrete masonry units or clay masonry units as illustrated in Figure 722.5.1(7), shall be permitted to be determined from the following expression:

(Equation 7-16)

where:

R=Fire-resistance rating of column assembly (hours).
W = Average weight of structural steel column (pounds per foot).
D=Heated perimeter of structural steel column (inches) [see Figure 722.5.1(7)].
Te=Equivalent thickness of concrete or clay masonry unit (inches) (see Table 722.3.2 Note a or Section 722.4.1).
K=Thermal conductivity of concrete or clay masonry unit (Btu/hr • ft • °F) [see Table 722.5.1(3)].
As=Cross-sectional area of structural steel column (square inches).
dm=Density of the concrete or clay masonry unit (pounds per cubic foot).
p=Inner perimeter of concrete or clay masonry protection (inches) [see Figure 722.5.1(7)].

722.5.1.4.6 Equivalent Concrete Masonry Thickness

For structural steel columns protected with concrete masonry, Table 722.5.1(5) gives the equivalent thickness of concrete masonry required for various fire-resistance ratings for typical column shapes. For structural steel columns protected with clay masonry, Table 722.5.1(6) gives the equivalent thickness of concrete masonry required for various fire-resistance ratings for typical column shapes.

Related Code Sections


722.5.1.4 Fire and Smoke Protection Features, Concrete-Protected Columns
The fire resistance of structural steel columns protected with concrete, as illustrated in Figure 722.5.1(6)(a) and (b), shall be permitted ...
Los Angeles Building Code > 7 Fire and Smoke Protection Features > 722 Calculated Fire Resistance > 722.5 Steel Assemblies > 722.5.1 Structural Steel Columns > 722.5.1.4 Concrete-Protected Columns
722.5.1.4 Fire and Smoke Protection Features, Concrete-Protected Columns
The fire resistance of structural steel columns protected with concrete, as illustrated in Figure 722.5.1(6) (a) and (b), shall be permitted ...
Los Angeles Building Code > 7 Fire and Smoke Protection Features > 722 Calculated Fire Resistance > 722.5 Steel Assemblies > 722.5.1 Structural Steel Columns > 722.5.1.4 Concrete-Protected Columns
722.5.1.4.2 Fire and Smoke Protection Features, Concrete Properties Unknown
If specific data on the properties of concrete are not available, the values given in Table 722.5.1(2) are permitted ...
Los Angeles Building Code > 7 Fire and Smoke Protection Features > 722 Calculated Fire Resistance > 722.5 Steel Assemblies > 722.5.1 Structural Steel Columns > 722.5.1.4 Concrete-Protected Columns > 722.5.1.4.2 Concrete Properties Unknown
722.5.1.4.4 Fire and Smoke Protection Features, Minimum Precast Concrete Cover
For structural steel columns protected with precast concrete column covers as shown in Figure 722.5.1(6)(a), Tables 722.5.1(9) and 722.5.1(10 ...
Los Angeles Building Code > 7 Fire and Smoke Protection Features > 722 Calculated Fire Resistance > 722.5 Steel Assemblies > 722.5.1 Structural Steel Columns > 722.5.1.4 Concrete-Protected Columns > 722.5.1.4.4 Minimum Precast Concrete Cover
722.5.1.4.4 Fire and Smoke Protection Features, Minimum Precast Concrete Cover
For structural steel columns protected with precast concrete column covers as shown in Figure 722.5.1(6)(a), Tables 722.5.1(9) and 722.5.1(10 ...
Los Angeles Building Code > 7 Fire and Smoke Protection Features > 722 Calculated Fire Resistance > 722.5 Steel Assemblies > 722.5.1 Structural Steel Columns > 722.5.1.4 Concrete-Protected Columns > 722.5.1.4.4 Minimum Precast Concrete Cover
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