Graduation of Martijn Helsdingen

Experimental modal validation of a semi-analytical method for assessing dynamic behaviour of flood gates

• Professor of graduation: Dr. Ir. B. Hofland (TU Delft)

• Supervisors of graduation: Dr. Ir. E. Lourens (TU Delft), Ir. O. C. Tieleman (TU Delft), Ir. E. De Almeida (TU Delft)

A new Semi-Analytical model is developed that enables to determine the dynamic response of slender flood gates with an overhang subjected to standing waves. The model is yet to be validated on its performance. This thesis aims for validation of the modal calculations performed by the Semi-Analytical model. Several experiments were executed in the wave flume at the faculty of Civil Engineering at the Technical University of Delft. Dry hammer tests, wet hammer tests and wave tests were executed for different water levels. Different plates took part in the experiments: Solid Plate and Reinforced Plate. A measurement plan was designed to obtain reliable results from the measurement devices (strain gauges and accelerometers). The experimental data was subjected to an Experimental Modal Analysis algorithm. The Frequency Domain Decomposition turned out to be most suitable for this situation. The mode shapes that were found were subjected to a Modal Assurance Criterion (MAC), in order to compare them with the semi-analytical prediction. The results from the wet modal analysis showed that the Solid Plate had good correspondence with the prediction of the semi-analytical model. The mode shapes turned out to have a high MAC value, while the natural frequencies showed small errors for the modes under consideration. The Reinforced Plate was less accurate. In the wave experiments the first three modes were found, which were also believed to have the highest energy input. Considerable high MAC values assured that the identified modes were indeed the same as the modes of the semi-analytical prediction. The natural frequencies showed larger errors for especially the first mode (approx. 50%).