Simplified methods of analysis described in codes and specifications for
seismically isolated structures are always used either directly in special cases or for
checking the results of nonlinear response history analysis (RHA). Important
predictions for seismically isolated structures by simplified methods are the
maximum displacements and base shears of the isolation system. In this study, the
maximum isolator displacements and base shears determined by nonlinear RHA are
compared with those determined by the equivalent lateral force (ELF) procedure in
order to assess the accuracy of the simplified method in the case of bi-directional
excitations with near-field characteristics. However, although there are currently
many methods for ground motion selection and scaling, little guidance is available
to classify which method is more appropriate than the others in any applications.
Features of this study are that the ground motions used in analysis are selected and
scaled using contemporary concepts and that the ground excitation is considered biv
directional. The variations in response of isolated structures due to application of
ground motions uni-directionally and bi-directionally are also studied by employing
a scaling procedure that is appropriate for the bi-directional analysis. The proposed
new scaling methodology is an amplitude scaling method that is capable of
preserving the horizontal orthogonal components and it is developed especially for
dynamic analysis of isolated structures. Analyses are conducted for two different
symmetric reinforced concrete isolated structure for two different soil conditions in
structural analysis program SAP2000. Effect of asymmetry in superstructure on
isolator displacement is also investigated with further analyses considering 5% mass
eccentricity at each floor level. Furthermore, once the significance of the orthogonal
horizontal component on the response of isolation system is shown, the biaxial
interaction of hysteretic behavior of lead rubber bearings is implemented in
OpenSees by developing a subroutine which was not readily available.
| Identifer | oai:union.ndltd.org:METU/oai:etd.lib.metu.edu.tr:http://etd.lib.metu.edu.tr/upload/3/12612039/index.pdf |
| Date | 01 June 2010 |
| Creators | Ozdemir, Gokhan |
| Contributors | Akyuz, Ugurhan |
| Publisher | METU |
| Source Sets | Middle East Technical Univ. |
| Language | English |
| Detected Language | English |
| Type | Ph.D. Thesis |
| Format | text/pdf |
| Rights | To liberate the content for public access |
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