An innovative procedure for the in-situ characterization of elastomeric bearings by using nanoindentation test

Control and inspection of the conditions of elastomeric bearings used for seismic isolation purpose is a fundamental activity in ensuring and preserving the performance of a structure. The methods currently used, such as visual inspections, Operational Modal Analysis (OMA), release tests, very often present strong limitations due to their qualitative nature or else to the costs associated with their implementation and functioning. An innovative procedure based on the use of nanoindentation tests is proposed and validated through an experimental campaign. Its main benefits consist in the possibility of quantitatively estimating the current characteristics of elastomeric bearings, in conjunction with low implementation costs and influence on the isolating devices. The innovative procedure consists of coring a very small sample of rubber from a bearing and testing it with a nano-indenter in order to estimate the actual characteristics in terms of shear stress-strain relationships. The experimental tests showed good agreement between the properties calculated with the proposed method and the ones obtained directly through a traditional shear test, making such procedure a promising tool.