Investigations on Inter-Storey Seismic Isolation as a Technique for Adding Upper Storeys

Abstract

The inter-storey seismic isolation technique is becoming increasingly attractive for the seismic risk mitigation of buildings, also as alternative strategy to base isolation. The reasons for applying this technique can be various and of different nature, such as: architectural concerns, feasibility of construction, and performance benefits. An interesting application of this technique concerns its use for adding upper storeys to existing buildings, avoiding the increase of seismic forces on the substructure, or even reducing them. Therefore, this technique could also be effective for seismic retrofit applications, using the mass of the superstructure as a nonconventional TMD for controlling the dynamic response of the substructure. Among the main issues concerning this application, there is the need to control the relative displacement between the two structural parts and the acceleration of the superstructure, while improving the seismic performance of the substructure. In this paper, a multi-objective optimization method for the dynamic characteristics of the additional superstructure is presented, which uses a TMD approach and considers the performances of the substructure, isolation system and superstructure. A 3-storey (3 DOF) case study structure was taken as a reference, analysing a wide range of isolated masses, isolation periods and damping ratios. Time-history analyses are finally performed, based on the optimization results, in order to assess the effectiveness of both the optimization method and the isolation technique, also considering the structural non-linearity.

Effectiveness of load-level isolation system for pallet racking systems

“…Various methods of TMD optimization are currently available, which differ mainly in the pursuit of different objective functions. Some of these maximize the effect of TMD (e.g., Sadek, 1997) or the energy dissipated by it (e.g., Reggio and De Angelis 2015); others minimize a certain structural response (e.g., Moutinho 2012;Zhou et al, 2016;Pietrosanti et al, 2017) or functions that take into account multi structural responses (e.g., Yahyai et al, 2019); still, some rely on multi-objective approaches to minimize primary structure response while controlling isolation drift or acceleration (e.g., Bernardi et al, 2021).…”

Intermediate Isolation System with Nonlinear Lower Structure and Isolation System

“…This paper examines the interesting idea of utilizing the IIS to extend vertically existing buildings for addressing the increasing demand for real estate in contemporary cities with almost no land take [2,3,11,12,[31][32][33][34][35][36][37]. In earthquake-prone zones, IIS can prevent any increase in seismic effects, despite the increase in mass due to the vertical extension.…”

Evaluation of the Inter-Story Isolation System Applied to an Existing Rc School Building

“…This aspect is beneficial, especially in densely populate areas [1]. Moreover, if properly designed, the IIS can improve the seismic performances of the existing structure, in fact, it can act as a non-conventional Tuned Mass Damper (TMD) for the substructure [6,7,8,9].…”

“…In this context, a large number of theoretical studies on IIS and TMD system are available in the literature, but only few investigations and optimization of the IIS for seismic retrofit of existing buildings [8,9,21,22,23].…”