SLENDERNESS OF COLUMNS IN BRACED FRAMES

Moment-magnification factors for columns in braced frames are dependen t upon column slenderness and the flexural stiffness of restraining be ams. A column bent in single curvature has a flexural stiffness that c an be as little as one-third that of the same column bent in reverse c urvature. Column slenderness ratios (L/R) above which reverse curvatur e moments must be magnified are significantly higher than those for wh ich single-curvature moments would require magnification. This paper s hows that when loading conditions are considered together with framing restraints, magnified moments from the single-curvature condition rar ely generate moment values as high as moments unmagnified from the rev erse-curvature loading condition. Thus, without need for moment magnif ication, column slenderness ratios can be significantly higher than th e limit ratios traditionally derived for single-curvature bending cond itions of columns.