Open AccessRetrofit of seismically isolated structures for near-field ground motion using additional viscous damping
Author(s) -
Lyle P. Carden,
B. J. Davidson,
Tam Larkin,
Ian G. Buckle
Publication year - 2005
Publication title -
bulletin of the new zealand society for earthquake engineering/nzsee quarterly bulletin
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.917
H-Index - 36
eISSN - 2324-1543
pISSN - 1174-9857
DOI - 10.5459/bnzsee.38.2.106-118
Subject(s) - ground motion , geology , base isolation , isolator , seismology , structural engineering , magnitude (astronomy) , peak ground acceleration , field (mathematics) , geotechnical engineering , physics , engineering , reduction (mathematics) , geometry , mathematics , pure mathematics , astronomy , electronic engineering
Recent earthquakes have shown that a large magnitude, long period pulse is often prevalent in ground motion records at sites within a few kilometres of the active fault during an earthquake. Near-field earthquake ground motion containing forward directivity effects can result in a larger response in flexible structures, such as seismically isolated structures, compared to that predicted for conventional ground shaking. Hence, a study was performed on a number of generic seismically isolated structures designed to the 1997 Uniform Building Code, as well as a case study on the William Clayton building in Wellington, to determine the impact of near-field ground motion. In optimising the performance of the buildings for both near-field and original "design level" earthquakes, it is concluded that linear viscous dampers added to the existing isolation systems are effective in controlling the response during large magnitude near-field earthquakes with minimal impact on the design response. Additional viscous damping is more effective than hysteretic damping in limiting isolator displacements while also preventing an increase in base shear and floor accelerations for far-field "design level" earthquakes.