HIGH PRECISION FORMULA FOR EFFECTIVE LENGTH FACTOR OF COLUMN IN UNBRACED FRAME

The objective of this study is to present a new high precision formula for effective length factor of column in unbraced symmetrical frame. The analytical model is a portal frame which gives the same buckling equation for a sub-assemblage frame. The formula is derived by equating the total complementary energy and external work of axial compression force. Although there are limitations to the range of G factors, it is shown that a relative error from the correct value ranges from -0.065%～0.26%. Moreover, an example is given and compared to precise result.