Abstract
Power spectral density of horizontal ground displacement of large and recent events in earthquake-prone Latin America is analyzed. The results confirm -in a larger region of the world- that strong motion horizontal displacement is a narrowband process, which was previously demonstrated solely on a very limited area: the State of California. Nonetheless, those limited and previous results proved to be important in seismic base isolation; particularly, in the solution of the problem of large displacements at the structure base. This is a current problem for which more expensive techniques than passive control are presently being implemented, as active or hybrid control; therefore, it is emphasized that a solution exists within simple base isolation, and it is based on ground displacement narrowbandness.
Highlights
Records of ground seismic displacement have not attracted much awareness because in dynamic analysis of conventional fixed structures, or the vast majority of buildings, ground acceleration records are the important signals [1,2,3]
It has been suggested that the reduction in absolute base displacement implies a reduction in relative base displacement because a) the latter is equal to the first minus the ground displacement record (u t − s t ) which is set or fixed and b) the before-reduction absolute displacement levels are larger than the ground displacement ones (u s) [4]
This idea or suggestion has not been demonstrated yet; actual relative or isolator displacement mitigation will be discussed in this work as an extension of the application of the results. This solution of the LBD problem was based on an important hypothesis regarding the modeling of the seismic input. This hypothesis in turn was based on a frequency-domain characterization of actual strong motion ground displacement, which was established through the analysis of the power spectral density (PSD) of displacement records of four (4) large California earthquakes [4]
Summary
Records of ground seismic displacement have not attracted much awareness because in dynamic analysis of conventional fixed structures, or the vast majority of buildings, ground acceleration records are the important signals [1,2,3]. It has been suggested that the reduction in absolute base displacement implies a reduction in relative base displacement because a) the latter is equal to the first minus the ground displacement record (u t − s t ) which is set or fixed (at least in a strong motion by strong motion basis) and b) the before-reduction absolute displacement levels are larger than the ground displacement ones (u s) [4] This idea or suggestion has not been demonstrated yet; actual relative or isolator displacement mitigation will be discussed in this work as an extension of the application of the results. This solution of the LBD problem was based on an important hypothesis regarding the modeling of the seismic input This hypothesis in turn was based on a frequency-domain characterization of actual strong motion ground displacement, which was established through the analysis of the power spectral density (PSD) of displacement records of four (4) large California earthquakes (moment magnitude above 7.0) [4]. It is noted that the suggested solution of the LBD problem is based on a linear model of the isolation system; there are nonlinear models [24] which require advanced numerical methods for the structural response [25]
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