Experimental characterization, design and modelling of the RBRL seismic‐isolation system for lightweight structures

Abstract

The Rolling-Ball Rubber-Layer (RBRL) system was developed to enable seismic isolation of lightweight structures, such as special equipment or works of art, and is very versatile, a great range of equivalent natural frequencies and coefficients of damping being achievable through choice of the system parameters.The necessity to have a simple and effective design procedure has led to a new parametric experimentation at Tun Abdul Razak Research Centre (TARRC) on the rolling behaviour of the RBRL system and load-deflection behaviour of the recentering springs. The experimental results, together with theories for the rolling resistance of a loaded steel ball on a thin rubber layer and the lateral load-deflection behaviour of cylindrical rubber springs, are used to develop a general design method for the RBRL system, which allows the system to be tailored to the specific application.Sinusoidal test results are presented for the small-deflection behaviour of the system, influenced by the presence of a viscoelastic depression on the rubber tracks beneath each ball, and an amplitude-dependent time-domain model is proposed, based on these results and on the steady-state behaviour of the system. The model is validated through comparison with previously performed shaking-table tests. Attention is here restricted to uniaxial behaviour.

Rolling devices for seismic isolation of lightweight structures and equipment. Design and realization of a prototype

“…In the study of Donà et al, the isolation device here proposed is similar to the RLRB isolators studied and designed in the present paper, but instead of cylinders, they used balls. The layers are flat, and the testing and auxiliary rubber recentering springs are utilized to recenter the structure after the earthquake motion.…”

Effectiveness of the RBRL Isolation System: Evidences From Seismic Tests and Numerical Simulation

“…The system comprises RBRL bearings and rubber recentering springs; these may be combined in single packages as shown in Figure 1 [1].…”

“…Previous studies [1,2,3,4] have shown that the RBRL system has three key types of behaviour, differentiated according to the magnitude of the displacements relative to the ground.…”

“…In this regime, for displacements greater than 15mm, the recentering rubber springs provide a well-defined natural frequency of isolation that need not be significantly amplitude dependent and can be designed to have any value. The equivalent linear damping level is determined predominantly by the rubber tracks, and for low design frequencies can be very high if desired [1], whereas for high frequency systems it may be necessary to use high damping rubber for the springs. The system thus behaves like a classical linear isolation system, but enables a wide margin for choice of natural frequency and damping ratio.…”

“…Extensive experimental studies of this system were undertaken by TARRC and collaborating research centres in the period 1993-1999 [in order 7,8,4,9,10,2], but a more comprehensive test and numerical characterization, a design method and a time-domain model for the simulation of the unidirectional behaviour of the same are more recent [1,3].…”