The experimental study of eccentrically braced frames with double vertical links

Abstract

This study proposes a new detail of vertical links for eccentrically braced frames. The research was conducted with two full-scale tests of double vertical links specimens under quasi-static cyclic loading. The first specimen was tested out of frame to study the overall stability and to determine seismic parameters. The second test utilized links on a single-story single-bay frame. The first specimen yielded at 200 kN with the displacement assumed to be δy = 1 mm. In the 30th to 31st cycle, a significant strength decay occurred. By the last cycle (about 300 kN), the specimen webs at the displacement of 25δy were ruptured. The second specimen yielded at the approximate force of 180 kN with an average displacement of 1.5 mm. By the displacement of 16δy, a significant strength decay occurred. In the 22nd cycle, with the same displacement, the web rupture. As a result, both specimens experienced their plasticity simultaneously and without time lag. The detail configuration causes small axial force and consequently the development of maximum shear strength in the links with a significant decrease in the moments at the ends of the beam. Therefore, the beams in the both specimens remained essentially elastic. The overall stability without providing lateral supports has been confirmed. The results of the proposed detail suggest stable and symmetric hysteresis loops, appropriate seismic behavior, and adequate ductility as required by design codes compared to single vertical links. In seismic rehabilitation, as ductile fuses develop out of framing, repalcing links after an earthquake is not concern.