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Earthquakes and Structures
  Volume 24, Number 3, March 2023 , pages 217-235
DOI: https://doi.org/10.12989/eas.2023.24.3.217
 


Extending the OPRCB Seismic isolation system's governing equations of motion to 3D state and its application in multi-story buildings
M. Hosseini, S. Azhari and R. Shafie Panah

 
Abstract
    Orthogonal pairs of rollers on concave beds (OPRCB) are a low-cost, low-tech rolling-based isolating system, whose high efficiency has been shown in a previous study. However, seismic performance of OPRCB isolators has only been studied in the two-dimensional (2D) state so far. This is while their performance in the three-dimensional (3D) state differs from that of the 2D state, mainly since the vertical accelerations due to rollers' motion in their beds, simultaneously in two orthogonal horizontal directions, are added up and resulting in bigger vertical inertia forces and higher rolling resistance. In this study, first, Lagrange equations were used to derive the governing equations of motion of the OPRCB-isolated buildings in 3D. Then, some regular shear-type OPRCB-isolated buildings were considered subjected to three-component excitations of far- and near-source earthquakes, and their responses were compared to those of their fixed-base counterparts. Finally, the effects of more realistic modeling and analysis were examined by comparing the responses of isolated buildings in 2D and 3D states. Response histories were obtained by the fourth-order Runge-Kutta-Nystrom method, considering the geometrical nonlinearity of isolators. Results reveal that utilizing the OPRCB isolators effectively reduces the acceleration response, however, depending on the system specifications and earthquake characteristics, the maximum responses of isolated buildings in the 3D state can be up to 40% higher than those in the 2D state.
 
Key Words
    3D analysis of base isolation; geometric nonlinearity; MATLAB platform; orthogonal pairs of rollers on concave beds (OPRCB) isolating system; Runge-Kutta-Nystrom method; time history analyses
 
Address
M. Hosseini: Department of Civil Engineering, Eastern Mediterranean University (EMU), 99628, Famagusta, North Cyprus via Mersin 10, Turkey
S. Azhari and R. Shafie Panah: Department of Earthquake Engineering, International Institute of Earthquake Engineering and Seismology (IIEES), Tehran, Iran
 

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