Performance analysis of aseismic base isolation systems for a multi-story building

A comparative study of the performances of several leading base isolation devices including the Rubber Bearing with and without lead core, the Sliding-Joint, the French System, and the Resilient-Friction isolator with and without upper sliding plate for a multi-story building under seismic ground accelerations is carried out. Several earthquake ground accelerations including El Centro 1940, Pacoima Dam 1971, and Mexico City 1985 earthquakes are considered. The acceleration, the base displacement and the structural deflection response spectra for the structure with different base isolation systems under various conditions are obtained and discussed. Several sensitivity analyses for variations in the parameters of the isolators and/or structure are also carried out. The effectiveness of various base isolators under a variety of conditions are studied and advantages and disadvantages of different systems are discussed. The results show that the acceleration transmitted and the column stresses of the structure can be effectively reduced by using properly designed base isolation systems. The results of the sensitivity analyses show the friction-type isolation systems are less sensitive to the variations in the amplitude and frequency content of the ground excitation in comparison to the Rubber Bearing base isolators. The study also shows that the peak accelerations transmitted by the friction-type isolators are not significantly affected by small variations in friction coefficient. Furthermore, variations in mass ratio and damping of the structure or the isolator do not significantly affect the peak responses.