313 Individual Columns

From an eigenvalue analysis, the general K-factor equation of an individual column as shown in Figure 31.1 is obtained as

-aC + —A- S -(C + S) hi det S C +—B- -(C + S) = 0 (31.2)


where the stability functions C and S are defined as

The largest value of K that satisfies Equation 31.2 gives the elastic buckling load of an end-restrained column.

Figure 31.2 (AISC 1989,1999; AASHTO 2004) summarizes the theoretical K-factors for end-restrained columns with some idealized end conditions. The recommended K-factors are also shown in Figure 31.2 for practical design applications. Since actual column conditions seldom comply fully with idealized end conditions used in buckling analysis, the recommended K-factors are always equal or greater than their theoretical counterparts.

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