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Earthquakes and Structures
  Volume 7, Number 6, December 2014, pages 1187-1221
DOI: http://dx.doi.org/10.12989/eas.2014.7.6.1187
 


A half-century of rocking isolation
Nicos Makris

 
Abstract
    The uplifting and rocking of slender, free-standing structures when subjected to ground shaking may limit appreciably the seismic moments and shears that develop at their base. This high-performance seismic behavior is inherent in the design of ancient temples with emblematic peristyles that consist of slender, free-standing columns which support freely heavy epistyles together with the even heavier frieze atop. While the ample seismic performance of rocking isolation has been documented with the through-the-centuries survival of several free-standing ancient temples; and careful post-earthquake observations in Japan during the 1940\'s suggested that the increasing size of slender free-standing tombstones enhances their seismic stability; it was George Housner who 50 years ago elucidated a size-frequency scale effect that explained the \"counter intuitive\" seismic stability of tall, slender rocking structures. Housner\'s 1963 seminal paper marks the beginning of a series of systematic studies on the dynamic response and stability of rocking structures which gradually led to the development of rocking isolation—an attractive practical alternative for the seismic protection of tall, slender structures. This paper builds upon selected contributions published during this last half-century in an effort to bring forward the major advances together with the unique advantages of rocking isolation. The paper concludes that the concept of rocking isolation by intentionally designing a hinging mechanism that its seismic resistance originates primarily from the mobilization of the rotational inertia of its members is a unique seismic protection strategy for large, slender structures not just at the limit-state but also at the operational state.
 
Key Words
    seismic protection; rocking frame; recentering; moment of inertia; earthquake engineering
 
Address
Nicos Makris: Division of Structures, Department of Civil Engineering, University of Patras, 26500 Patras, Greece
 

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