Localizing nonlinear behavior from response measurements

The process of characterizing a nonlinearity can be defined as determining three things; location, type, and functional form. In the present study it is investigated if the random decrement technique can be used in an output-only setting for one of these; localizing nonlinear behavior. The localization is performed through a novel random decrement analysis procedure of the time history of each response measurement in a multiple degrees-of-freedom system. The analysis will detect nonlinear behavior, if present, and indicate the degree of the nonlinear behavior. A numerical test case is investigated using the analysis procedure, where a localized nonlinear element is located at various discrete locations of a T-shaped structure. Two types of nonlinearities, and three locations are investigated. Results indicate that it is not possible to explicitly determine at which degree-of-freedom a nonlinear element resides. It is, however, possible to determine which degrees-offreedom that are affected by the nonlinear element.