FIGURE 14.4 Nomenclature of an I-shaped cross-section.

Section (for a compact section) and Section (for a noncompact section). The equations for the maximum unbraced girder length Lb are reproduced as follows:

For compact sections:

ry E FyC

where Mj is the the smaller of the two end moments of the unbraced length of the girder due to factored loading, Mp is the plastic moment of the cross-section, ry is the minimum radius of gyration of the cross-section, E is the elastic modulus, and Fyc is the specified minimum compression flange yield stress.

For noncompact sections:

where E and Fyc are as defined in Equation 14.7, rt is the radius of gyration of a notional cross-section composed of the entire compression flange and one third of the depth of the compression portion of the web, taken about the vertical axis of the section.

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