Mechanical model of the over-stroke displacement behaviour for double concave surface slider anti-seismic devices

Abstract

For double concave curved surface slider (DCCSS) isolators with a flat rim and lacking restrainers, such as those most commonly used in Europe, the rigid slider can exceed the geometrical capability of the housing plate during earthquakes stronger than those produced in simulations. During this over-stroke displacement, DCCSSs preserve the ability to support superstructure gravity loads and the capacity to dissipate energy. There are currently no applicable hysteresis rules or available algebraic solutions that can be used to predict over-stroke behaviour for response-history analysis. This study presents an algebraic solution to extend basic theories for estimating the actual limit displacement of DCCSS devices with over-stroke capacity. DCCSS behaviour in the over-stroke sliding regime was modelled with a focus on geometrical compatibility and kinematics. The proposed analytical formulation was calibrated on the basis of experimental controlled-displacement tests performed on single DCCSS devices. A case study of a six-storey reinforced concrete frame isolated building was modelled using a combination of non-linear elements that are currently available in several structural analysis software packages and able to correctly model over-stroke displacement behaviour for non-linear time history analyses. The DCCSS model was augmented with a friction model capable of accounting for torsional effects, axial load, and velocity variabilities. Comparison with non-linear dynamic analysis outcomes shows that the forces and displacements in the over-stroke sliding regime are predictable and therefore useful for the designer.

Retrofitting of R.C. Frame Buildings With Double Con-Cave Curved Surface Isolator Sliders Characterized by Over-Stroke Displacement Capacity

“…The overstroke ultimate displacement dlim corresponds to the slider overturning around its center of rotation beyond the geometrical capacity or to the maximum contact pressure between the rigid slider and housing plate, equal to the slider surface reduced by the area of the slider external to the sliding [18].…”

Advanced Modelling and Risk Analysis of RC Buildings with Sliding Isolation Systems Designed by the Italian Seismic Code

“…To properly represents the isolators over-stroke displacement, the basic OpenSEES model (SingleFPBearing) has been modified by adding three zero-length parallel hinges from j-node to k-node of Figure 7b). The numerical model calibration of DCCSS over-stroke displacement has been carried out with reference to experimental characterization tests performed on similar bearings [18,24,40,41], the main parameters of the numerical model are reported in Table 4.…”

Seismic rehabilitation of existing RC school buildings with under-designed joints by means of reinforced jacketing of high performance fiber reinforced cementitious composite (HP-FRCC)

“…Vailati et al 2021) or by means of Concave Curved Surface Sliders (CCSS) (e.g. Bianco et al 2019Bianco et al , 2021aDall'Asta et al 2020;Braga et al 2022;Di Cesare et al 2022). Even though the base isolation is the most effective technique, the isolators must be designed very carefully and some inconveniences can be posed by the need to have a suitable space around the isolated building to accommodate the resulting displacements.…”