Study on influence of stress softening of rubber material due to damage on earthquake response

Abstract

Mullins effect is the phenomenon of stress softening due to prior straining. Stress softening affects the response of facilities isolated by rubber bearings to strong earthquakes because it changes the stiffness of rubber bearings. The influence of the Mullins effect on seismic responses needs to be understood in detail in order to design facilities isolated by rubber bearings based on performance design. The stiffness of rubber isolators which is affected by stress softening, varies over time because stress softening changes depending on the number of repetitions of straining and the magnitude of the generated strain. The magnitude of strain generated in a facility before the principle seismic motion of an earthquake reaches the facility differs depending on whether the earthquake is subduction-zone earthquake or an active fault earthquake because the principle seismic motion of an active fault earthquake reaches the facility in a shorter time. This paper presents the results of a study to investigate the influence of stress softening caused by the Mullins effect and differences in the seismic response of a facility depending on the characteristics of earthquakes.

Keywords

• earthquake
• seismic isolation
• rubber
• mullins effect
• stress softening