Experimental Study of Using Vertical Link Beam to Improve Seismic Performance of Steel Buildings

Passive control methods, by reducing seismic demand and increasing ductility, can reduce magnitude of seismic damage. One of the most effective passive control methods is vertical shear link or shear panel system (SPS), in which vertical shear link pieces are installed between node of chevron braces and the flange of floor beam. In designing this system, the vertical link beam first yields and dissipates seismic energy, and the remaining elements would stay elastic. Unlike eccentrically braced frames, EBFs, these pieces are not embedded in floor and can be exchanged easily with least effort and less cost after earthquakes.In this paper, five tests were conducted on five specimens of steel braced frames having vertical shear links in different lengths and sections. The results of tests show that the overall performance of these pieces is convincing. In all specimens, shear distortion in vertical shear links varied between 0.128 and 0.156 rad before failure. All specimens had stable hysteretic curves and showed good energy dissipation. Also other structural elements like beams, columns and braces remained elastic. Averages ratios of equivalent viscous damping in specimens varied between 26.7 and 30.6%. In all specimens that had one or more stiffeners (except SPS1 where its weld failed) ductility coefficients reached about 7. Also response modification factors of specimens varied between 7.15 and 10.65 (while 7.15 belonged to SPS1 and response modification factors of other specimens were in range of 8.97 to 10.65 and had more compatibility and less dispersion). Overall, performances of vertical shear links regarding energy dissipation and ductility increase were satisfactory based on experimental results.