Efficiency of helical springs and viscodampers in base isolation

Abstract

Results of an experimental testing are presented for a five-storey steel frame model, subjected to horizontal and vertical earthquake vibrations with varying intensities. The dynamic testing included the fixed base conditions, as well as full isolation by means of neoprene pads and helical springs, coupled with or without viscous dampers. The response of the structural model to both horizontal and vertical vabrations has been thoroughly recorded, and these records have been correlated with those of the analytical investigations. The main conclusion of the study is that the vertical vibrations may unexpectedly cause response amplifications at very high undesirable levels, especially when the structure is base isolated by means of rubber pads. No such deficiency occurs, however, when helical springs and viscodampers are used.