An in-house numerical model developed at McMaster University was used in this research to investigate the effect of the wave breaking on the performance of Tuned Liquid Damper (TLD). In this model, the Volume Of Fluid VOF method was used to construct the free surface and the surface tension was taken into consideration to evaluate the wave breaking. The model was implemented on incompressible, 2D flow water within the TLD that was harmonically excited. . The ability of the TLD to cancel out the external excitation was examined via damping effectiveness of the TLD. The damping effectiveness is calculated as the ratio of the net energy experienced by the TLD to the input excitation energy; both energies were calculated as the area under the force-displacement curve. The investigation of the effect of the wave breaking was done through changing the fluid height ratios, amplitude and frequency ratios. The fluid height ratio was changed as h/L= 0.5, 0.35, 0.125 which is above and at and below the critical fluid level for wave breaking occurrence respectively. The critical height is defined as the height at which the waves start to break. It was found that at high fluid ratios wave breaking did not occur, in contrary, at critical level wave breaking did occur and even more breaking waves recorded to have taken place at much lesser levels. The effect of the fluid height ratio on the damping effectiveness of the TLD was investigated, it was seen that the damping effectiveness of the TLD improves as water level becomes shallower. The amplitude ratio was also examined; the behavior of the TLD in general did not change i.e. increasing the amplitude enhances the damping of the TLD. The frequency ratio range was selected to cover the near-resonance region. It was found that the TLD damps most excitation close to the resonance. The wave breaking occurrence was assured via the free surface visualization for several cases and found in agreement with different wave breaking shapes reported experimentally. / Thesis / Master of Applied Science (MASc)