Page 217 - Structural Steel Designers Handbook AISC, AASHTO, AISI, ASTM, and ASCE-07 Design Standards

Brockenbrough_Ch04.qxd 9/29/05 5:09 PM Page 4.45

BUILDING CODES, LOADS, AND FIRE PROTECTION*

BUILDING CODES, LOADS, AND FIRE PROTECTION 4.45

weight per unit length of the member (lb/ft), and D is the inside perimeter of the fire protection
material (in). Expressions for calculating D are illustrated in Fig. 4.15 for columns and beams with
either contour or box protection. In short, the weight-to-heated-perimeter ratio defines the thermal
size of a structural member.
Since the temperature of a structural steel member is strongly influenced by W/D, it therefore
follows that the required thickness of fire-protection material is also strongly influenced by W/D.

FIGURE 4.15 Equations for determining the heated perimeter D of structural steel members (a) columns
and (b) beams.

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