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

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.

[1]  M. A. Rahgozar,et al.  Accounting for soil nonlinearity in three-dimensional seismic structure-soilstructure-interaction analyses of adjacent tall buildings structures , 2015 .

[2]  Khoshnoudian Faramarz,et al.  RESPONSE OF PURE-FRICTION SLIDING STRUCTURES TO THREE COMPONENTS OF EARTHQUAKE EXCITATION CONSIDERING VARIATIONS IN THE COEFFICIENT OF FRICTION , 2009 .

[3]  Michel Bruneau,et al.  Ductile design of steel structures , 1997 .

[4]  Goodarz Ahmadi,et al.  Seismic isolation of buildings with sliding concave foundation (SCF) , 2003 .

[5]  T. C. Liauw,et al.  Structures on sliding base subject to horizontal and vertical motions , 1988 .

[6]  Firdaus E. Udwadia,et al.  Periodic response of a sliding oscillator system to harmonic excitation , 1983 .

[7]  James M. Kelly,et al.  Aseismic base isolation: review and bibliography , 1986 .

[8]  Touraj Taghikhany,et al.  Effect of variation of normal force on seismic performance of resilient sliding isolation systems in highway bridges , 2004 .

[9]  Iradj G. Tadjbakhsh,et al.  Response of Sliding Rigid Structure to Base Excitation , 1984 .

[10]  M. Davoodi,et al.  Assessment of near-field and far-field strong ground motion effects on soil-structure SDOF system , 2015 .

[11]  The frictional behavior of materials under vertical vibration , 2009 .

[12]  Andrei M. Reinhorn,et al.  Teflon Bearings in Base Isolation II: Modeling , 1990 .

[13]  A. Fuladgar,et al.  Response of pure-friction sliding structures to three components of earthquake excitation , 2003 .

[14]  H. Shakib,et al.  Minimizing the torsional response of asymmetric wall-type systems considering soil-structure interaction , 2014 .

[15]  Goodarz Ahmadi,et al.  Performance analysis of aseismic base isolation systems for a multi-story building , 1991 .

[16]  Goodarz Ahmadi,et al.  Stochastic earthquake response of structures on sliding foundation , 1983 .

[17]  Lin Su,et al.  Probabilistic responses of base-isolated structures to El centro 1940 and Mexico city 1985 earthquakes , 1992 .

[19]  Goodarz Ahmadi,et al.  Numerical modeling of MDOF structures with sliding supports using rigid‐plastic link , 2001 .

[20]  N. Null.  Minimum Design Loads for Buildings and Other Structures , 2003 .

[21]  Goodarz Ahmadi,et al.  Multi-story base-isolated buildings under a harmonic ground motion — Part I: A comparison of performances of various systems , 1990 .

[22]  Michael C. Constantinou,et al.  Verification of friction model of teflon bearings under triaxial load , 1993 .

[23]  Goodarz Ahmadi,et al.  Response of frictional base isolation systems to horizontal-vertical random earthquake excitations , 1988 .

[24]  Abolhassan Vafai,et al.  Response of structures supported on SCF isolation systems , 2003 .

[25]  Ahmad Naderzadeh.  Application of seismic base isolation technology in Iran , 2009 .

[26]  Mohammad Asaduzzaman Chowdhury,et al.  The effect of amplitude of vibration on the coefficient of friction for different materials , 2008 .