Experimental Studies on the Elastic-Plastic Behavior of Braced Frames under Repeated Horizontal Loading. Part 3 Experiments of One Story-One Bay Braced Frames

Abstract

Experimental studies have been conducted to investigate the hysteretic behavior of one story-one bay braced steel frames whose braces are made of built-up H-shapes and whose columns and beams are made of rolled H-shapes. Hysteretic behavior and transition and change of load carrying capacity of each component member of a frame, i.e., braces, columns and beams under repeated horizontal load are examined individually as well as the hysteretic behavior of a braced frame as a whole. Interaction behavior between the braces built in a frame and the components of the surrounding frame is also discussed. As a fruit of the investigation, the following is remarked. The effective slenderness ratio for buckling of the braces built in a frame could be estimated by the slope-deflection method taking the rotational rigidity by the members of the surrounding frame into account. Since hysteretic behavior of the braces built in the surrounding frame, the dimensions of whose component members are comparable with those of the brace is not much different from that of the brace reported in Part 1 which was approximately rigidly fixed in the heavy surrounding frame, the effect of the deformation of the members of the surrounding frame on the hysteretic behavior of the brace would not be large. The effective slenderness ratio for the estimation of the post-buckling and hysteretic behaviors could be approximated by the assumption that the braces would be rigidly fixed at the ends. As the columns are subjected to large repeated axial load due to the deformation of the brace and the load carrying capacity of the column largely decreases when the axial load is large, the behavior of the column is largely affected by that of the brace. The load carrying capacity and the ductility of the brace are reduced and exhausted when cracks are initiated as well as reported in Part 1 and Part 2.