Introducing a multi-layer pendulum isolator and investigating its effect on structures' responses during some earthquakes

Abstract

To protect structures from earthquakes, various systems called base isolation are used, which reduce the force applied to the structure during ground movement by reducing the lateral stiffness of the structure. This makes the structure follow the movement of the earth, but softly and with a delay in response. In this research, an isolator with a new shape is proposed without having permanent displacement, similar to a pendulum, and can be used as an isolation system in structures. This system is called a multi-layer pendulum isolator. The system has the same period as a tall pendulum but is much smaller in size. The equations of the isolator were derived and solved by MATLAB software. Examples of frames were modeled in Abaqus under several earthquakes, and the responses of the system were obtained. Results showed that the proposed isolator reduced acceleration, drift, and base shear very effectively. For example, by using a multi-layer pendulum isolator in a six-story frame, it was found that the base shear and drift created in the first floor were reduced by more than sixty percent. The multi-layer pendulum isolator introduced showed that it was an efficient isolator system capable of reducing the destructive effects of an earthquake. The results of the system responses showed that the system reduced the maximum acceleration of the earthquake by more than seventy percent. The results of the FFT analysis showed that by using a suitable damper with a damping coefficient of more than ten percent, no resonance would occur in the system. Two different heights of the multi-layer isolators were compared. It was shown that for the isolator with a height of eighty centimeters, about twice as much material was used as for the isolator with a height of forty centimeters, but no significant improvement was observed in the results.