Triangular Pyramid Scissor-Jack-Damper for Enhanced Stability and Efficiency

Scissor-jack-damper (SJD), an advanced variant of the toggle-brace-damper, has encountered some small-to-medium applications in several practical projects. The application of large SJD is rather limited because it suffers out-of-plane instabilities, which is due to the SJD's planar configuration tagged by a low out-of-plane stiffness. To fix up this problem and to further explore the advantage of the SJD mechanism, the authors of this paper utilize an asymmetric 3D arrangement of rods and dampers to generate a triangular pyramid “3 dampers - 6 rods” layout. The novel structuring scheme exhibits not only an enhanced robustness with better global stability but also an elevated efficiency. In this study, the displacement amplification factor, force amplification factor, and the equivalent damping coefficient of the proposed SJD are derived, wherein the force equilibrium (or energy conservation in a substitutive process) and the geometrical compatibility are accounted for. Taylor's series expansion and a simplified truncation are adopted to process the nonlinearity of the spatial SJD. The accuracy of the theoretical expression is proved against numerical modelling. It is shown that the equivalent damping coefficient of the dampers integrated in the novel SJD can be amplified by more than 10 times via a reasonable design configuration. The included angle θ between the rods plays the most important role in adjusting the amplification factor η of the SJD, e.g, the value of η drops from 14.01 to 7.13 as θ increases from 15° to 25° in a typical design scheme. An illustrative applicational example of the proposed SJD is provided. Compared with the conventional damper installation configuration, the 4-story demonstrative frame equipped with the proposed SJD shows a 52 % and a 26 % reduction in the peak roof displacement and the peak base shear, respectively.