Evaluation of horizontal stiffness of fibre‐reinforced elastomeric isolators

Summary Unbonded fibre-reinforced elastomeric isolator (U-FREI) is relatively new seismic base isolator in which fibre layers are used as reinforcement to replace steel shims as are normally used in conventional isolators. Further, the top and bottom end steel connector plates of conventional isolators are also removed. In general, the horizontal response of U-FREI is nonlinear because of reduction in contact area due to rollover deformation and reduction in shear modulus of isolator under large deformation. Thus, evaluation of horizontal stiffness of U-FREI is a challenging problem. Most previous studies were focused on the investigation of horizontal response of scaled models of U-FREIs with low shape factors. A few analytical approaches were suggested for predicting the horizontal response of U-FREI; but their results were not in good agreement with experimental observations. In the present study, the horizontal responses of prototype U-FREIs are evaluated under a constant vertical pressure and cyclic loading using both experiments and finite element analysis. Prototype U-FREIs with different shear moduli and with different shape factors are considered. Finite element simulations of corresponding bonded FREIs are also performed under the same loadings as in U-FREIs. A rational analytical approach including the influence of rollover deformation and simultaneous reduction in shear modulus is proposed as a basic analytical tool for predicting the horizontal stiffness of FREIs (both bonded and unbonded). It is in reasonably good agreement with the results obtained from experiments and numerical analysis. Copyright © 2017 John Wiley & Sons, Ltd.

[1]  Alfred Strauss,et al.  Experimental investigations of fiber and steel reinforced elastomeric bearings: Shear modulus and damping coefficient , 2014 .

[2]  Robert G. Drysdale,et al.  Bonded versus unbonded strip fiber reinforced elastomeric isolators: Finite element analysis , 2011 .

[3]  Robert G. Drysdale,et al.  Simplified analysis of a low-rise building seismically isolated with stable unbonded fiber reinforced elastomeric isolators , 2009 .

[4]  Anjan Dutta,et al.  Performance of fiber‐reinforced elastomeric base isolators under cyclic excitation , 2015 .

[5]  Satish Nagarajaiah,et al.  Stability of Elastomeric Seismic Isolation Bearings , 1999 .

[6]  Gerhard A. Holzapfel,et al.  ON LARGE STRAIN VISCOELASTICITY: CONTINUUM FORMULATION AND FINITE ELEMENT APPLICATIONS TO ELASTOMERIC STRUCTURES , 1996 .

[7]  Satish Nagarajaiah,et al.  Stability of Elastomeric Isolation Bearings: Experimental Study , 2002, Journal of Structural Engineering.

[8]  L. Mullins.  Softening of Rubber by Deformation , 1969 .

[9]  Alfred Strauss,et al.  Verbesserte Bemessungsrichtlinien für Bewehrte Elastomerlager , 2011 .

[10]  Ray W. Ogden,et al.  A constitutive model for the Mullins effect with permanent set in particle-reinforced rubber , 2004 .

[11]  Alp Caner,et al.  Comparison of fundamental properties of new types of fiber‐mesh‐reinforced seismic isolators with conventional isolators , 2014 .

[12]  Gaetano Russo,et al.  Sliding instability of fiber-reinforced elastomeric isolators in unbonded applications , 2013 .

[13]  Xing Han,et al.  Identification of the Controlling Mechanism for Predicting Critical Loads in Elastomeric Bearings , 2013 .

[14]  Robert G. Drysdale,et al.  Lateral Response Evaluation of Fiber-Reinforced Neoprene Seismic Isolators Utilized in an Unbonded Application , 2008 .

[15]  Ali Akbar Aghakouchak,et al.  Design, manufacturing and evaluation of the performance of steel like fiber reinforced elastomeric seismic isolators , 2008 .

[16]  R. Ogden.  Large deformation isotropic elasticity – on the correlation of theory and experiment for incompressible rubberlike solids , 1972, Proceedings of the Royal Society of London. A. Mathematical and Physical Sciences.

[17]  Gilberto Mosqueda,et al.  Static and Dynamic Stability of Elastomeric Bearings for Seismic Protection of Structures , 2013 .

[18]  Dimitrios Konstantinidis,et al.  Finite element analysis of unbonded square fiber-reinforced elastomeric isolators (FREIs) under lateral loading in different directions , 2014 .

[19]  Dimitrios Konstantinidis,et al.  Experimental and finite element study on the compression properties of Modified Rectangular Fiber-Reinforced Elastomeric Isolators (MR-FREIs) , 2014 .

[20]  Giorgio Serino,et al.  Innovative low-cost recycled rubber–fiber reinforced isolator: Experimental tests and Finite Element Analyses , 2014 .

[21]  Hamid Toopchi-Nezhad,et al.  Horizontal stiffness solutions for unbonded fiber reinforced elastomeric bearings , 2014 .

[22]  J. Kelly.  Analysis of Fiber-Reinforced Elastomeric Isolators , 1999 .

[23]  M. Shahria Alam,et al.  Performance of carbon fiber-reinforced elastomeric isolators manufactured in a simplified process: experimental investigations , 2014 .

[24]  Beom-Soo Kang,et al.  Design and manufacturing of fiber reinforced elastomeric isolator for seismic isolation , 2002 .

[25]  James M. Kelly,et al.  Tension Buckling in Multilayer Elastomeric Bearings , 2003 .