EVALUATION METHOD FOR THE EFFECTIVE LENGTH FACTOR OF LONG COLUMNS IN SWAY MODE UTILIZING HORIZONTAL STIFFNESS OF THE FRAME

The horizontal stiffness method (the HS method) is proposed as an accurate approach to evaluate the effective length factor of columns when a frame with long columns buckles in a sidesway mode, utilizing the horizontal stiffness derived by the first-order analysis. A parametric study was conducted to investigate the accuracy of the method. Based on the numerical results, the HS method can evaluate the effective length factor of a long column in a frame with an accuracy of 5~6%. The Ai distribution (the Japanese design shear force distribution) is recommended for the story shear force in the first-order analysis.