Creep effects on elastomeric and ball rubber bearings under sustained lateral loads

Base isolation applications are becoming popular in the seismic design of resilient structures and infrastructures. Even though the response of the bearings is widely studied under cyclic displacements, limited information is available for bearing response under sustained lateral loads. These types of loads can develop sustained lateral displacement in the bearing. During the holding time under sustained lateral displacement, the creep or stress relaxation may significantly change the properties of the bearings and may affect the response in the reloading stage. This research paper aims at assessing the influence of short-term lateral creep on the hysteretic response of rubber bearings, and ball rubber bearings. To this end, experimental testing on different elastomeric bearings under imposed lateral displacement is performed. For each device, the lateral response is measured, and the advantages and disadvantages are discussed in terms of strength, stiffness, energy dissipation and equivalent damping. The loss of load under sustained lateral displacement is experimentally assessed and the effects of creep in the design procedure of a base isolated system are discussed.