Paper Title
An Efficient Horizontal Stiffness Solution for Unbonded-Frebs

Abstract
Unbonded-Fiber Reinforced Elastomeric Bearings (U-FREBs) area new type of elastomeric bearings that are placed between their top and bottom supports without any bonding. When subjected to lateral loads, U-FREBs exhibit rollover deformation which means that their top and bottom faces roll off the contact supports. As such, the lateral response characteristics of U-FREBs is different than conventional steel reinforced elastomeric bearings that are fixed to their top and bottom supports. The literature includes a set of analytical models for horizontal stiffness evaluation of U-FREBs. However, these models are not so effective to provide accurate estimation for a wide range of bearing physical dimensions. This paper presents a finite element analysis calibrated analytical model for horizontal stiffness evaluation of U-FREBs. The model has been calibrated based on the results of finite element analysis of a large group of bearings of different physical dimensions . The accuracy of the presented model is preserved for bearings of different shape factors. Keywords- seismic isolators; fiber reinforced elastomeric bearing; unbounded application; horizontal stiffness; finite element analysis; shape factor; aspect ratio