Effects of superstructure flexibility on the response of base-isolated structures

A parametric study of base-isolated structure with different isolation systems is conducted for investigating the effects of superstructure flexibility. The superstructure is idealized as a one-storey structure isolated by different systems such as elastomeric bearings (with and without lead core) and sliding systems. The governing equations of motion of the isolated structural system are derived and the response of the system is obtained for stochastic model of earthquake ground motion. The earthquake ground motion is modeled as a uniformly modulated non-stationary random process. The stochastic response of isolated structure is obtained using the state variable approach. An equivalent linearization technique is used for the approximate response of isolated structure with non-linear isolation systems. The mean square superstructure acceleration and bearing displacement of the system are plotted under different system parameters and compared with the corresponding response of rigid sup erstructure condition to study the influence of superstructure flexibility. The comparison of response is made under various isolation system parameters (i.e. isolation period, damping, yield strength of elastomeric bearings and friction coefficient of sliding systems). It is observed that the bearing displacement can accurately obtained by modelling the superstructure as a rigid body in a base-isolated structure. However, such approximation may under-estimates the superstructure acceleration under certain conditions.

[1]  R. S. Jangid,et al.  Seismic behaviour of base-isolated buildings : a state-of-the-art review , 1995 .

[2]  R. S. Jangid,et al.  Base isolation for near‐fault motions , 2001 .

[3]  Yeong-Bin Yang,et al.  Response of multi‐degree‐of‐freedom structures with sliding supports , 1990 .

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

[5]  James M. Kelly,et al.  Base Isolation: Linear Theory and Design , 1990 .

[6]  R. S. Jangid,et al.  Dissipation of Hysteretic Energy in Base Isolated Structure , 1996 .

[7]  Alfredo H.-S. Ang,et al.  Nonstationary Stochastic Models of Earthquake Motions , 1968 .

[8]  M. Livolant,et al.  Seismic isolation using sliding-elastomer bearing pads , 1985 .

[9]  Goodarz Ahmadi,et al.  Floor response spectra for base‐isolated multi‐storey structures , 1990 .

[10]  H. Saunders,et al.  Introduction to Random Vibration , 1986 .

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

[12]  R. S. Jangid,et al.  EFFECTIVENESS OF ELLIPTICAL ROLLING RODS FOR BASE ISOLATION , 1998 .

[13]  R. Clough,et al.  Dynamics Of Structures , 1975 .

[14]  M. Khodaverdian,et al.  Dynamics of resilient‐friction base isolator (R‐FBI) , 1987 .

[15]  James M. Kelly,et al.  The Analysis of Multilayer Elastomeric Bearings , 1984 .

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

[17]  Y. Wen.  Method for Random Vibration of Hysteretic Systems , 1976 .

[18]  Ronald L. Mayes,et al.  Seismic Isolation: History, Application, and Performance—A World View , 1990 .

[19]  T. Caughey.  Equivalent Linearization Techniques , 1962 .

[20]  Naser Mostaghel,et al.  Response of sliding structures to earthquake support motion , 1983 .

[21]  Goodarz Ahmadi,et al.  WIND EFFECTS ON BASE-ISOLATED STRUCTURES , 1992 .