Floor Seismic Response Spectrum for the Building Equipped with Visco-Elastic Decouplers

By installing the visco-elastic (VE) decouplers between the floor slab and the beam, the floors of a building are isolated from the primary structure. Such a structural system, termed VE decoupled floors, has an increased damping and a reduced inertial force for mitigating the floor seismic response. These features lead to a significantly improved seismic performance of the important facilities resting (or anchored) on floors. This paper focuses on the floor seismic response spectrum (FSRS) of the building equipped with VE decoupled floors. First, the frequency-dependent property of the structure is dealt with, whereas the time-variant stiffness and damping of the VE decoupler are replaced by a couple of stabilized substitutions, and the appropriation of this substitution is numerically validated. Secondly, given the stabilized substitutive model, the FSRS is derived based on the classic complex modal decomposition process and the stochastic dynamics of linear oscillators. In this process, the input seismic excitation is considered via a specific model that accounts for its non-stationary nature. Lastly, a parametrical analysis is conducted to validate the proposed FSRS model and to reveal some special features of the VE decoupled flooring system. It is shown that the FSRS can be better mitigated if a more flexible VE decoupler and a larger mass (isolation) ratio are incorporated. A VE decoupled floor installed at the level of the roof is more effective than the ones installed at the lower levels. Basically, the peak of FSRS can be reduced by 70% if the VE decoupling system is properly designed.