Advertisement

International Journal of Civil Engineering

, Volume 15, Issue 2, pp 287–298 | Cite as

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

  • Majid MohammadiEmail author
Research Paper

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.

Keywords

Friction Sliding base Instantaneous frequency Instantaneous amplitude Restitution coefficient 

List of Symbols

a

A constant in Formula (2)

COR

Coefficient of restitution

Fb

Friction load between the block and ground

Fn

Normal load

k

A constant in Formula (2)

g

Gravitational acceleration (9.81 m/s2)

mb

Block mass

N

Instantaneous vertical reaction

V

Relative velocity of the contacting surfaces

timpact

Time duration of the impact

\( X_{\text{b}} \)

Block absolute horizontal displacement

\( X_{\text{g}} \)

Ground absolute horizontal displacement

\( \dot{X}_{\text{b}} \)

Block horizontal velocity

\( \dot{X}_{\text{g}} \)

Ground horizontal velocity

\( {\ddot{X}}_{\text{b}} \)

Block horizontal acceleration

\( {\ddot{X}}_{\text{g}} \)

Ground horizontal acceleration

\( Y_{\text{b}} \)

Block absolute vertical displacement

\( Y_{\text{g}} \)

Ground absolute vertical displacement

\( {\ddot{Y}}_{\text{b}} \)

Block vertical acceleration

\( {\ddot{Y}}_{\text{g}} \)

Ground vertical acceleration

α

A constant in Formula (1)

ub

Block velocity just before hitting the ground

ug

Ground velocity just before the block hits the ground

vb

Block velocity after the hitting the ground

vg

Ground velocity just after the block hits the ground

μ

Friction coefficient of the layer

µs

Static friction coefficient

µmax

The maximum coefficients of friction

µmin

The minimum coefficients of friction

Notes

Acknowledgments

This research study has been accomplished by financial support of International Institute of Earthquake Engineering and Seismology under the Grant No. 7385 and their contribution is highly appreciated.

References

  1. 1.
    Rahgozar MA (2015) Accounting for soil nonlinearity in three-dimensional seismic structure-soil structure-Interaction analyses of adjacent tall buildings structures. Int J Civil Eng 13(3):213–225Google Scholar
  2. 2.
    Shakib H, Atefatdoost GR (2014) Minimizing the torsional response of asymmetric wall-type systems considering soil-structure interaction. Int J Civil Eng 12(1):14–24Google Scholar
  3. 3.
    Davoodi M, Sadjadi M (2015) Assessment of near-field and far-field strong ground motion effects on soil-structure SDOF system. Int J Civil Eng 13(3):153–166Google Scholar
  4. 4.
    Naderzadeh A (2009) Application of seismic base isolation technology in Iran. Menshin 63:40–47Google Scholar
  5. 5.
    Kelly J (1986) Aseismic base isolation: review and bibliography. Soil Dyn Earthq Eng 4(3):202–216CrossRefGoogle Scholar
  6. 6.
    Constantinou M, Mokha A, Reinhorn A (1990) Teflon bearings in base isolation. II: modeling. J Struct Eng ASCE 116(2):455–474CrossRefGoogle Scholar
  7. 7.
    Westermo B, Udwadia F (1983) Periodic response of a sliding oscillator system to harmonic excitation. Earthq Eng Struct Dyn 11:135–146CrossRefGoogle Scholar
  8. 8.
    Younis CJ, Tadjbakhsh IG (1983) Response of sliding rigid structure to base excitation. J Eng Mech ASCE 110(3):417–432CrossRefGoogle Scholar
  9. 9.
    Ahmadi G (1983) Stochastic earthquake response of structures on sliding foundation. Int J Eng Sci 21(2):93–102CrossRefzbMATHGoogle Scholar
  10. 10.
    Su L, Ahmadi G (1988) Response of frictional base isolation systems to horizontal–vertical random earthquake excitations. Probab Eng Mech 3(1):12–21CrossRefGoogle Scholar
  11. 11.
    Su L, Ahmadi G (1992) Probabilistic responses of base-isolated structures to El Centro 1940 and Mexico City 1985 earthquakes. Eng Struct 14(4):217–230CrossRefGoogle Scholar
  12. 12.
    Fan F-G, Ahmadi G, Tadjbakhsh IG (1990) Multi-story base-isolated buildings under a harmonic ground motion—Part I: a comparison of performances of various systems. Nucl Eng Des 123:1–16CrossRefGoogle Scholar
  13. 13.
    Fan F-G, Ahmadi G, Mostaghel N, Tadjbakhsh IG (1991) Performance analysis of aseismic base isolation systems for a multi-story building. Soil Dyn Earthq Eng 10:152–171CrossRefGoogle Scholar
  14. 14.
    Matsui K, Iura M, Sasaki T, Kosaka I (1991) Periodic response of a rigid block resting on a footing subjected to harmonic excitation. Earthq Eng Struct Dyn 20:683–697CrossRefGoogle Scholar
  15. 15.
    Vafai A, Hamidi M, Ahmadi G (2001) Numerical modeling of MDOF structures with sliding supports using rigid-plastic link. Earthq Eng Struct Dyn 30:27–42CrossRefGoogle Scholar
  16. 16.
    Hamidi M, El Naggar MH, Vafai A (2003) Response of structures supported on SCF isolation systems. Earthq Eng Struct Dyn 32:1555–1584CrossRefGoogle Scholar
  17. 17.
    Hamidi M, El Naggar MH, Vafai A, Ahmadi G (2003) Seismic isolation of buildings with sliding concave foundation (SCF). Earthq Eng Struct Dyn 32:15–29CrossRefGoogle Scholar
  18. 18.
    Khoshnoudian F, Haghdoust V (2009) Response of pure-friction sliding structures to three components of earthquake excitation considering variations in the coefficient of friction. Sci Iran Trans A Civil Eng 16(6):429–442Google Scholar
  19. 19.
    Liaw TC, Tian QL, Cheung YK (1988) Structures on sliding base subjected to horizontal and vertical motion. J Struct Eng ASCE 114:2119–2129CrossRefGoogle Scholar
  20. 20.
    Shakib H, Fuladgar A (2003) response of pure-friction sliding structures to three components of earthquake excitation. Comput Struct 81:189–196CrossRefGoogle Scholar
  21. 21.
    Takahashi Y, Iemura H, Yanagawa S, Hibi M (2004) Shaking table test for frictional isolator. In: Proceeding of 13th world conference on earthquake engineering, Vancouver, CanadaGoogle Scholar
  22. 22.
    Iemura H, Taghikhany T, Takahashi Y, Jain S (2005) Effect of variation of normal force on seismic performance of resilient sliding isolation systems in highway bridges. Earthq Eng Struct Dyn 34:1777–1797CrossRefGoogle Scholar
  23. 23.
    American Society of Civil Engineers (1994) Minimum design loads for buildings and other structures, vol. 7. American Society of Civil Engineers, RestonCrossRefGoogle Scholar
  24. 24.
    Iranian Code of Practice for Seismic Resistant Design of Buildings (2015) Standard No. 2800, Road, Housing and Urban Development Research Center of I. R. IranGoogle Scholar
  25. 25.
    Bruneau M, Uang CM, Sabelli SR (2011) Ductile design of steel structures. McGraw Hill Professional, New YorkGoogle Scholar
  26. 26.
    Mokha AS, Constantinou MC, Reinhorn AM (1993) Verification of friction model of teflon bearings under triaxial load. J Struct Eng ASCE 119:240–261CrossRefGoogle Scholar
  27. 27.
    Chowdhury MA, Helali M (2008) The effect of amplitude of vibration on the coefficient of friction for different materials. Tribol Int 41:307–314CrossRefGoogle Scholar
  28. 28.
    Chowdhury MA, Helali M (2009) The frictional behavior of materials under vertical vibration. Ind Lubr Tribol 61(3):154–160CrossRefGoogle Scholar
  29. 29.
    Misiti M, Misiti Y, Oppenheim G, Poggi JM (1996) Wavelet toolbox. The MathWorks Inc., NatickzbMATHGoogle Scholar

Copyright information

© Iran University of Science and Technology 2017

Authors and Affiliations

  1. 1.International Institute of Earthquake Engineering and Seismology (IIEES)TehranIslamic Republic of Iran

Personalised recommendations