Development of rocking-column (ROC) seismic base isolation system for buildings

2020-10-21
Javed , Nasir
Earthquake mitigation of buildings has been a long-standing matter of research. Researchers have proposed many systems that can be categorized as passive control, active control, and hybrid systems. Seismic base isolation, usually linked to the passive control category, is a well-known technique to isolate a structure from harmful effects of earthquakes. In this research, a new seismic isolation system, different from the conventional seismic base isolation systems, has been proposed and named as Rocking-Column (ROC) seismic isolation system. The working principle of ROC is to isolate a building by the use of story-high rocking columns. The study is inspired from earthquake response of ancient rocking columns used in Greek Civilization as well as Pagoda structures constructed mostly in Japan, where the first floor or all stories are flexible and behave like isolators. The research comprises following stages: 1) comprehensive review of the literature regarding rocking of rigid blocks, 2) development of a nonlinear numerical model in commercially available software (SAP2000), which simulates the rocking column behavior, 3) experimental validation of the numerical model via testing of small scale prototypes, 4) analyses of different ROC seismically isolated building models (2D, 3D, mass and stiffness vertical irregularities), and 5) development of preliminary design guidelines for ROC seismic isolation systems installed in medium rise residential buildings. Analyses results have proven that the width and height (slenderness) of rocking rectangular columns are the most important parameters which outline the performance of the ROC seismic isolation systems. Other parameters that influence the effectiveness of the ROC seismic isolators include the nature and magnitude of earthquakes, total number of floors, and column bay size of buildings. The simulation results have demonstrated that ROC systems indubitably isolates buildings even for largest earthquakes. Additionally, the suggested “restraining mechanism” in the ROC isolation system prevents any total collapse of buildings. The proposed system may be applied to existing buildings, which may also provide an additional parking space or an extra floor. The outcome of the analyses showed that the ROC system generally performs better than that of the conventional isolation systems of laminated rubber bearing (LRB) and friction pendulum system (FPS). The proposed ROC seismic isolation system may provide an alternative to the existing seismic isolation systems for medium rise buildings. The major design parameters of a) ROC’s column height and base width (slenderness), b) number of stories, c) bay size (5m or 7.5m), d) different earthquake records are changed and responses for i) overturning, ii) floor accelerations, iii) interstory drifts, and iv) first floor total shear were obtained in graphical format, which then helped to produce preliminary design tables of the ROC isolator system for medium rise residential buildings.

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Citation Formats
N. Javed, “Development of rocking-column (ROC) seismic base isolation system for buildings,” Ph.D. - Doctoral Program, Middle East Technical University, 2020.