Numéro : 2638 - Year : 2013
Conversion matrix: how to post-treat local measurements to evaluate the global loads
Fabien BIGOT, BUREAU VERITAS – Division MarineBUREAU VERITAS – Division Marine
Quentin DERBANNE, BUREAU VERITAS – Division Marine
Eric BAUDIN, BUREAU VERITAS – Division Marine
In full scale measurements as in model tests it is impossible to measure directly the hull girder loads. A conversion matrix usually combines the different strain or motion measurements and yields the different internal load values, at one or several locations. In this paper we show that all the different possible procedures to obtain the internal loads from strain measurements can be seen as variations of a single general procedure. First, a base of distortion modes is built using a structural model. Then a conversion matrix is used to project the measured values on the distortion modes base, and the internal loads are obtained by recombination of their modal values. These last two steps are often merged in a single conversion matrix. The case of a ultra large container ship instrumented with strain gauges is used. Several types of distortion mode bases are considered, and compared.