Ricerc@Sapienza

A widespread approach for the prediction of the structural response as function of the ground motion intensity is based on the Cloud Analysis: once a set of points representing the engineering demand parameter (EDP) values is obtained as function of the selected seismic intensity measure (IM) for a collection of unscaled earthquake records, a regression analysis is performed by assuming a specific functional form to correlate these variables.

The equivalent linearization is a well-known simplified approach for estimating the maximum absolute displacement of inelastic systems, being widely adopted in many technical codes and guidelines. In this regard, the present paper addresses the use of the equivalent linearization to estimate the peak displacement of bilinear oscillators with known displacement ductility subjected to near-fault pulse-like earthquakes. An extensive numerical investigation is initially performed in order to evaluate the accuracy of a recent equivalent viscous damping formulation.

Even if the effectiveness of friction pendulum bearings has been extensively proven by means of numerous experimental programs carried out worldwide, many aspects concerning their behavior under seismic action still need to be clarified.

The assessment of maximum displacement demand is a crucial point in the design of seismic
isolating systems, in particular when the non linear behaviour of devices is modeled
through visco-elastic equivalent schemes, as common in the design practice. Several phenomena
influence the maximum demand assessment, among which the torsional and earthquake
directionality effects can be of great impact. International codes use some formulations
which allow to consider torsional effects, while the impact of the other phenomena

Nowadays, seismic retrofit through isolation strategy represents a consolidated technique of protection against design earthquakes. This technique is also applied on existing structures extensively, due to the fact that it usually does not require any interruption of the building use and occupants evacuation. If applicable, it rapidly allows the seismically retrofitting of a building installed with seismic devices with low horizontal stiffness between the structure and the foundation decoupling, in fact, this allows the motion of the superstructure from the ground one.