EFFECT OF ANCHORAGE REBARS APPLYING TO MID-STORY PIN COLUMN BASE CONNECTION ON STRESS TRANSFER MECHANISM AND ULTIMATE SHEAR STRENGTH UNDER HORIZONTAL FORCE

Abstract

Mid-story pin column system has been proposed to realize beam yielding mechanism of a steel moment-resisting frame. In this system, a pin connection system is applied inbetween the upper steel column and the lower RC column extended from the base beam to control moment demands on both ends of the first story column. An exposed-type column base has been adopted as a pin connection connected by a single anchor bolt. Static cyclic horizontal loading tests of a partial frame consisting of the first story column and the second floor beams showed a frame with the proposed column base system exhibited stable hysteresis performance up to a story drift angle of 0.05 rad, remaining column in elastic. In addition, the RC column with the connection of a single anchor bolt exhibited slippage at the connection while this problem was solved when an anchor bolt was stiffened by cross-shaped four shear plates. A cover plate was also welded on the top of the shear plates to cover the top surface of the RC column from bearing pressure of the upper steel column. An anchor bolt with the welded plates are called an anchor bolt set, or ABS, hereinafter. Ensuring a reliable seismic performance of an upper steel frame, damages at the proposed connection have to be minimized. So far, compressive stress transfer mechanism was clarified, and the ultimate compressive strength of the connection was evaluated in the previous study.