توسعه تاریخی سیستم های جداساز لرزه ای مبتنی بر اصطکاک
Abstract
1- Introduction
2- The “pendolo Viscardini” (1909)
3- The friction pendulum system (1980s)
4- Development of low friction materials
5- Development of multi-surface sliders
6- Two European case studies
7- Open problems and current developments
8- Conclusions
References
Abstract
Base isolation has emerged as one of the most effective high-tech strategies for protecting infrastructure under seismic loading. This review paper discusses the historical development of friction-based seismic isolation systems, focusing on systems that have successfully been deployed and used as seismic safety measures for structures located in Europe. The conception and implementation of the Friction Pendulum system, the development of low friction materials and the effects of heating, contact pressure and velocity are discussed in light of past and recent numerical and experimental evidence. The merits of multiple surface devices, namely the Double Curvature Friction Pendulum and the Triple Friction Pendulum are also discussed, along with current knowledge and research gaps. Two European case studies, the Bolu Viaduct and the C.A.S.E. Project, are presented to illustrate that sliding base isolators can be used to meet otherwise unachievable design objectives. Finally, existing problems such as the response to high vertical accelerations, the potential for bearing uplift and the relevance of residual displacement are analyzed.
Introduction
In today's “performance-based” context, one effective way of protecting structures, and achieving a desired performance, is to mitigate the seismic demand on the system itself. To this end, one of the most promising solutions identified over the past few decades consists of installing low lateral stiffness devices, referred to as base isolators, beneath key supporting points of the structure. Base isolation has emerged as one of the most effective high-tech strategies for protecting infrastructures under seismic loading, both in the context of new construction, and in the retrofit of existing systems. The goal of base isolation is normally to prevent the structure from damage, by shifting the fundamental period of a structure to the long period range and by absorbing the full displacement demand induced by seismic ground motions at the isolation layer. Isolating a structure results in a controlled structural response with reduced accelerations and lateral forces transmitted to the structure. The reduced seismic demand allows the superstructure to remain elastic, or nearly elastic, following a design level event. Furthermore, isolating a structure contributes to reducing the likelihood of damage to displacement sensitive and acceleration sensitive equipment, nonstructural components, and content. Extensive research has been conducted on the topic of base isolation over the past few decades and the volume of information available in the literature has grown significantly, particularly in the last 15–20 years. To this end, a number of excellent reviews of aspects of the development, theory, and application of this technology can be found in the literature (e.g. [1–7] amongst many others). However, given the amount of research available on base isolation, no single paper can provide an exhaustive literature review. Thus, authors are forced to either provide a general discussion of the topic, at the cost of providing limited details, or to provide detailed discussions, focusing only on selected issues. Furthermore, there is a steadily increasing production of new numerical and experimental literature, as a result of growing interest in the subject.