Boundary condition error for parametric updating of in-operation systems : Application to piping systems

There is an increasing interest in experimental analysis of in-operation structures where a part of the boundary conditions is poorly known. This concerns particularly the case of coupled systems where some complex physical phenomena make the behaviour of both the system and its connectivity dependent on the functioning conditions. In this context, this paper presents a new frequency approach for parametric structural updating in the vibration and acoustic fields. This methodology is developed here in the case of piping systems. It follows the boundary conditions identification method previously developed by the authors. A boundary conditions error is presented and its efficiency to translate structural parameters error is shown. Thus, the proposed approach allows performing the identification of some unknown boundary conditions and, simultaneously, updating the model of the tested structure. The pertinence of a frequency choice criteria based on the smallest singular value of the solved system during the identification of the boundary conditions is shown. It specifically allows avoiding the bands of critical frequencies. The developed updating technique is tested with two actual cases: a laboratory test case and an industrial example.