Shake table test a structure retrofitted using 2-4 Direction Displacement Dependent (D3) viscous dampers
Many seismic codes are modified to represent increased hazard or performance expectations of structures. According to the new code, many structures require retrofit to meet these increase performance expectations. Fluid viscous dampers can add energy dissipation without requiring major structural modification. However, their addition can lead to substantial increases in the maximum base shear and column axial forces in non-linear structures. In practice, these increases in demand would likely require strengthening of the columns and the foundations, thus increasing cost and reducing the ease and potential impact of this approach. In contrast, the 2-4 configuration of a passive Direction and Displacement Dependent (D3) damper provides damping in only quadrants 2 and 4 of the force-displacement response plot, thus substantially reducing peak base shear loads compared to a conventional viscous damper. The paper looks at the seismic performance of a 1/2 scale, two storey steel frame building that is retrofitted with the passive 2-4 D3 damper subjected to uni-directional shake table testing. Performance in mitigating structural response and foundation demand are assessed by evaluating base shear, maximum drift and acceleration. The overall results show that simultaneous reductions in displacement, base-shear and acceleration demand are only available with the 2–4 D3 viscous device. This device is entirely passive, and provides unique retrofit opportunity that does not require strengthening of the columns and the foundations.