THE DAMPING PROPERTIES OF A STEEL STRUCTURAL MODEL WITH A BOX-SHAPEDWATER RESERVOIR UPON TOP FLOOR

A swimming pool or a reservoir on the roof of the high-rise building may contribute to the damping behavior of the building structure underneath due to the earthquake shake. The water waves in the swimming pool due to earthquake shake produce additional force to the building due to the change of momentum and vise versa. The structure's response supporting the reservoir in the form of lateral deformation and natural frequency is highly influenced by water depth, reservoir dimensions, stiffness of the structure, and the loading patterns. There is an interaction among water waves, box-shaped reservoir, and the structural elements underneath. A study was carried out with a numerical simulation using the DualSPHysics application using a box-shaped reservoir of 200 mm long, with widths of 50 mm, 75 mm, and 100 mm. The reservoir was shaken under lateral sinusoidal forces with various frequencies to produce the maximum force on the reservoir wall. Besides that, a three-story steel structural model having dimensions of 500x500 mm floor plan and 1200 mm high was tested under free vibrations with the box-shaped reservoir as mentioned above. The numerical simulation result indicates that at d/L ratios up to 0.144, the maximum resultant force is still increasing. On the other hand, at the free vibration test of the experimental model, the optimum of damping ratios (xi) can be indicated by the decreasing lateral amplitudes of the structural model at d/L between 0.2 and 0.4 and at about the natural frequency of the structure i.e 2.2439 Hz.