Single-story steel structure with LVEM-isolated floor: Elastic seismic performance and design response spectrum

The seismic demand of a structure could be reduced by isolating the floors using laminated visco-elastic materials (LVEM). Such a LVEM-isolated floor system exhibits many advantages, such as the embedded large mass isolation ratio, the mitigation of floor acceleration, the easy-to-demolish characteristic, etc. This paper focuses on the elastic seismic performance of single-story steel structures equipped with the LVEM-isolated floor system, wherein the LVEM-isolators are made of acrylic visco-elastic materials. The numerical simulating approach and the dynamic analysis procedure are developed for the structural system. In the procedure, the LVEM isolators are simulated by the Kelvin-Voigt model. The numerical simulating approach is validated by shaking table tests. Based on the results of an extensive response history analysis, the effects of several key parameters on the elastic structural seismic demand are quantified. The considered parameters include the structural natural period (T), the mass-isolation ratio, and the stiffness of the LVEM isolators. The displacement response spectra for both the substructure and the LVEM isolators, namely, the lambda(S) - T spectra and the lambda(VEM) - T spectra, are developed corresponding to the ambient temperature theta = 20 degrees C. In the structural design, lambda(S) is used for checking the seismic capacity of the substructure, while lambda(VEM) is used for determining an appropriate deforming space for the LVEM isolators. The seismic demand of the substructure generally decreases as the LVEM isolators become more flexible and the mass-isolation ratio becomes larger. The effect of ambient temperature-changing on the proposed elastic design spectra is analyzed. Generally, such effect is more pronounced when the mass-isolation ratio increases and the stiffness of the LVEM isolator decreases. Analysis data is provided for quantifying the effect of ambient-temperature-changing on the lambda(S) - T spectra and the lambda(VEM) - T spectra. Based on the data, the structural design and evaluation could be carried out efficiently.