STUDY ON EFFECTIVE LENGTH FACTOR OF COLUMN IN FRAME-SHEAR WALL DUAL LATERAL FORCE-RESISTANT SYSTEM

For the frame-shear wall dual lateral force resistance system, the lateral stiffness of the frame and the shear wall could be reflected comprehensively by the stiffness characteristic values, and investigated its influence on the shear force-sharing ratio and stable bearing capacity of frames. Four analytical models with heights of 48 m, 72 m, 96 m and 120 m were established. The finite element method and the simplified calculation method were used to estimate the stable bearing capacity of the structures and the effective length coefficient of the frame columns respectively. The stiffness characteristic value can comprehensively reflect the relative stiffness of the frame and the shear wall as well as the influence of the structure height. The larger the characteristic stiffness value is, the larger the shear force shared by the frame is. The frame buckling load modified coefficient γ can be used to quantitatively characterize the degree to which the frame is subjected to the lateral support of the shear wall, and γ decreases rapidly with the increase of the structure height. When the height of the frame-shear wall is large, the buckling load of the frame part may be lower than that of the pure frame, indicating that the frame part provides lateral support for the shear wall at this time. The calculation results show that, for the pure frame, the effective length factor of the column obtained by the finite element analysis through segmental loading of the standard stories of the structure remains unchanged within the range of each standard stories, and there is little difference between standard stories. Based on the method of mutual support of the same-story columns in the modified "Steel Structure Design Standard" GB50017, the effective length factor of the column is relatively close to the result of the segmental loading finite element analysis, and the error range is −9.5% to 14.2%. For frame-shear wall structures, the calculated length factor of the column is between the unbraced frame and the braced frame, as the height of the structure increases, its value is gradually close to that of the pure frame. The effective length factor obtained by the method in GB50017 method is close to the result by segmental loading finite element analysis. Since the axial force of the column gradually decreases with the increase of the floor height, the effective length factor of the column is continuously increased according to Euler's formula, which indicates that the finite element model with story-by-story loading has limitations in determining the effective length factor of the column. The method can be used as a reference when determining the effective length coefficient of columns in frame-shear wall dual lateral force resistance structures.