In Scale Model of the Bridge for System Identification. (2016) - Sokol, Milan
Abstract: The article deals with a part of structural health monitoring (SHM) of in scale model. Investigated experimental model is similar to the bridge situated in the western part of Slovakia. After laboratory tests, the work continued with in-situ monitoring of original bridge. During the first stage of testing only the basic dynamic characteristics - mass and stiffness have been verified. Therefore, the different boundary conditions were assumed and namely boundary conditions for cantilever beam instead of those for simply supported beam. This set up allowed for easier construction of boundary conditions. Many difficulties have occurred during the preparation and validation, e.g. different thickness of individual cross-sections, modelling of hinge joints according to the experimental model, modelling of real supports, appropriate parameters of bolts, etc. It was necessary to measure every single cross-section because of the big variation between them. The emphasis was done to modelling of the selected joints especially of the set of 6 bolts on two diagonals of the bridge. The changes in dynamic characteristics according to the different numbers of bolts in a joint have been measured. At the beginning, the natural frequencies were calculated and compared with the test for both cases of model boundary conditions. Modal analysis of the structure was performed in FEM software ANSYS. After a few steps of tuning, the result was sufficiently precise and the difference between measured and analyzed results was small. Finally, the test set up and numerical model similarity was quite acceptable. The next step which is currently being started is the investigation of the damage in joints of two diagonals. The methodology of dynamic testing appropriate for the identification is now being verified.