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

Felice Carlo Ponzo,Alessio Telesca,Marco Furinghetti,Alberto Pavese,Antonio Di Cesare

doi:10.3390/app11041938

Abstract

Double Curved Concave Surface Sliders (DCCSS) are seismic isolators based on the pendulum principle widely used worldwide. Coherently with European code, DCCSS do not include any mechanical elements as end-stopper. In case of displacement higher than those associated with the design earthquakes, the inner slider runs on the edge of the sliding surfaces beyond their geometric displacement capacity keeping the ability to support gravity loads. In this paper, the advanced modelling and risk analysis of reinforced concrete (RC) base-isolated buildings designed for medium and high seismicity zones according to the Italian code has been assessed considering new construction and existing structures retrofitted using the seismic isolation technique. Pushover analyses and nonlinear dynamic analyses including inelastic superstructure behaviour and the over-stroke displacement of the isolation system have been carried out. Annual rates of failure are computed for Usability-Preventing Damage (UPD) related to the superstructure inter-storey drift and for Global Collapse (GC) associated with the ultimate displacement of the DCCSS. Moreover, the ultimate displacement is assumed with an extra-displacement of more than 30% of the maximum geometrical displacement. Results pointed out that in the case of new buildings the GC and UPD conditions occur almost at the same seismic intensity, while for the cases of the existing building, the UPD is the dominant limit state, being reached at an intensity level lower than GC.

Highlights

Base isolation is one of the most used techniques for the seismic protection of buildings
This paper presents the results of an ongoing RINTC research project investigating the global collapse (GC) and the usability preventing damage (UPD) limit states of reinforced concrete (RC) buildings with isolation systems based on double concave curved surface sliders (DCCSS)
Starting from the same 6-storey prototype building, four case studies of isolation systems have been designed considering two different sites, characterised by medium and high seismicity, and including two existing structures retrofitted through the base isolation technique

Summary

Introduction

Base isolation is one of the most used techniques for the seismic protection of buildings. It has long been known that seismic isolation technology is one of the most effective solutions to protect new and existing buildings at both serviceability and ultimate limit states [2,3]. Recent research works have highlighted the main dependency of the frictional properties on some important response parameters, such as the sliding velocity, the recentering capacity, the contact pressure, the temperature rise during the sliding motion and the consequences of mounting laying defects for curved surface slider devices [11,12,13,14,15]. It has been observed that the friction coefficient decreases as the contact pressure rises, due to fluctuations induced by either the vertical component of the seismic event or overturning effects, while the recentering capability depends only on the characteristics of the isolation system. Differences in the effects of radial and bidirectional motions should be noticed

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