Seismic Behavior of Sliding Base Isolation Systems, Regarding Restitution Factor and Variable Friction Coefficient: Fid-Bau Portal

Seismic Behavior of Sliding Base Isolation Systems, Regarding Restitution Factor and Variable Friction Coefficient

Mohammadi, Majid

Abstract Sliding foundation is a technique to suppress seismic loads applied to structures. There are many studies showing that sliding foundations are efficient especially for low rise buildings; however, most of them have ignored the effects of vertical components of the earthquake records on the behavior of such bases. This paper focuses on influences of sliding foundations on seismic behavior of low rise buildings, for real cases. For this purpose, vertical component of earthquakes is considered as well as inherent properties of foundation material such as coefficient of restitution (COR). Furthermore, variation of friction coefficient during the earthquake is considered. COR is utilized to consider bouncing of the structure after separation of the foundation, occurred for extreme downward vertical accelerations (greater than gravitational acceleration). Variation of friction coefficient is considered based on a new study, showing that the coefficient of friction depends on instantaneous amplitude and frequency of the vertical excitation. The obtained results show that vertical component of earthquake affects the behavior of the sliding base substantially. It is also demonstrated that providing material for the sliding base with higher COR is advantageous in decreasing structural acceleration response. Furthermore, the coefficient of friction is really lower than the regularly assumed values and, therefore, leads to smaller structural acceleration response but mostly greater residual displacements.