Partial floor mass isolation to control seismic stress in framed buildings

Isolating portions of the floor mass through rigid–plastic connectors may reduce the effects of strong earthquakes on framed buildings. This strategy was shown to be effective for single-storey frames, provided that a reasonably low plastic limit given to connectors and large enough portions of mass be disconnected. The stress reduction is however found to depend significantly on some interrelated parameters and on the given earthquake. By means of an analytical study and a nonlinear numerical investigation involving single-storey frames and four recorded earthquakes, the present paper gives a swift way to estimate the extent of stress reduction that can be achieved under a given earthquake, for preset values of the key parameters. Some empirical formulae are also provided to estimate the peak relative displacement that is reached by the disconnected mass.