The 2DOF model was developed in order to mach the first two modal characteristics (frequency and damping
ratio) as well as the anti-resonance (fixed base frequency) were similar with the ones of the base isolated building. It
consists of two springs having a total stiffness ki that link the ground to mass mi, and second pair of springs with a
total stiffness ks that link the mass mi to mass ms. The masses are supported by roller bearings over the shaking table