Shear stress distribution of unbonded reinforced elastomeric bearings after lift-off occurs

•Analytical solution for the shear strain distribution including lift-off effects is derived.•Eight FEA bearing models are considered to validate the analytical lift-off behaviour.•The numerical and analytical moment-rotation relationship agree well.•Bearings with more layers have a larger numerical result for maximum shear strain.•Bearings with more layers show more significant global effects. Reinforced elastomeric bearings (REBs) are widely used to accommodate displacements in bridges as well as for seismic isolation applications. For unbonded REBs, lift-off (i.e. separation between the superstructure and the bearings) could occur under certain combinations of large rotations and relatively low axial stress. Canadian and American bridge design codes (i.e. CSA S6 and AASHTO) have inconsistent requirements in the regulation of lift-off. The objective of this study is to validate the existing analytical solution of the moment-rotation relationship for unbonded REBs considering lift-off by finite element analysis (FEA). The analytical solution, which accounts for the compressibility of the elastomer and extensibility of the reinforcement, has not yet been validated. The shear strain distribution in the elastomeric layers of unbonded REBs is derived and validated by FEA. Eight infinite strip-shaped bearings with different number of layers are investigated. The results show that the numerical curves fit well with the analytical curves in terms of the overall tendency. The analytical solutions could be used to predict the behaviour of unbonded REBs subjected to lift-off. The numerical results of the moment-rotation relationship were more agreeable to the analytical solutions for the unbonded bearings with fewer number of layers and under smaller loads.