Influence of ground motion characteristics on the optimal single concave sliding bearing properties for base-isolated structures

Abstract

This study examines the influence of ground motion characteristics on the optimal friction properties of single concave sliding bearings employed for the seismic isolation of structural systems. The evaluation of the optimal properties is carried out by considering a non-dimensional formulation which employs the peak ground acceleration (PGA) and the peak ground acceleration-to-velocity (PGA/PGV) ratio as ground motion parameters. A two-degree-of-freedom (2dof) model is employed to describe the isolated system and two different families of records representative respectively of near fault and far field seismic inputs are considered. Following the nondimensionalization of the equation of motion for the proposed ground motion parameters, it is shown that the non-dimensional responses obtained for the two types of seismic inputs are similar. This result confirms that PGA/PGV is a good indicator of the frequency content and of other characteristics of ground motion records, helping to reduce the scatter in the response. Regression expressions are also obtained for the optimal values of the friction coefficient that minimizes the superstructure displacements relative to the base as a function of the abovementioned ground motion parameter and of the dimensionless system parameters. These expressions can be used for the preliminary estimation of the optimal properties of isolation bearings with a single concave sliding surface or double concave sliding surfaces with equal friction coefficient

Seismic reliability-based ductility demand for hardening and softening structures isolated by friction pendulum bearings

“…In Castaldo and Ripani, the optimal values of the friction coefficient have been provided by means of multivariate nonlinear regression expressions depending on the system properties and on the soil condition in order to minimize the superstructure response with the observation that higher values of the optimal friction coefficient are necessary for soft soil condition. In Castaldo and Tubaldi, the optimal values of the friction coefficient taking into account the influence of the ground motion characteristics by means of the ratio PGA/PGV have been proposed. The seismic performance of bridges isolated with FPS considering different limit states (LSs) has been investigated in Castaldo and Lo Priore …”

Simplified Method for Optimal Design of Friction Damper Slip Loads by Considering Near-Field and Far-Field Ground Motions

“…According to their results, under the near-field earthquakes with fling-step effect, the base isolation proved to be ineffective in terms of reducing base shear, top storey absolute acceleration and maximum inter-storey drift. In a more recent study, Castaldo and Tubaldi (2018) investigated the effects of ground motion characteristics on the optimum friction pendulum properties of seismic isolation systems. It was shown that PGA/PGV is a better indicator of the frequency content of the input ground motion compared to PGA, and can help to provide less scatter predictions.…”

Full Scale Tests of the Base-Isolation System for an Emergency Hospital

“…Despite the static and dynamic behavior of these systems has been deepen analyzed in the recent years also by the experimental point of view [4][5][6][7][8], very few studies about the in-situ behavior of structures equipped with FPIs are available nowadays.…”