Ga

where Y1 indicates the summation of all members rigidly connected to the joint and lying in the plane in which buckling of column is being considered, and subscripts c and g represent columns and girders, respectively.

Equations 31.5 and 31.6 can be expressed in the form of alignment charts as shown in Figure 31.4. It is noted that for columns in braced frames, the range of K is 0.5 < K< 1.0; for columns in unbraced frames, the range is 1.0 < K<1. For column ends supported by, but not rigidly connected to, a footing or foundations, G is theoretically infinity, but unless actually designed as a true friction-free pin, it may be taken as 10 for practical design. If the column end is rigidly attached to a properly designed footing, G may be taken as 1.0 (AISC 1999).

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