Seismic performance of mass-variable tuned liquid dampers with particles fluidization in building applications

A conventional tuned liquid damper (TLD) generates a relatively small control force associated with low density of sloshing water. To overcome this main drawback, proposed in this study is a new TLD system composed of water and fine particles in a rectangular tank of sloping bottom. When subjected to a weak base excitation, the fine particles inside the rectangular tank remain at the bottom of the tank, and the water above the particles sloshes with a free surface. As the base excitation increases, the fine particles appear in a fluidized state due to increased pore pressure between particles; the particles and the water in the tank are then mixed and sloshing together, this increasing the mass of sloshing body. The new TLD system has larger effective mass, stronger adaptability to external excitations, larger control force, and more flexible geometry design. In this study, the behavior and response of water sloshing, single particle, single layer of particles and multiple layers of particles were investigated both experimentally and numerically. Image analysis was performed to determine the wave height of sloshing motion, the displacement, velocity and acceleration of particles from experimental data. A multiple virtual flat-bottom tanks model was proposed to evaluate the motion of particles and water sloshing in a rectangular tank. It was experimentally proven sufficiently accurate for engineering applications. The effectiveness of the proposed mass-variable TLD system is validated with extensive shake table tests. It was concluded that the motion of a particle can be simulated with sufficient accuracy under weak excitations as long as the linear wave theory is applicable. In comparison with a conventional TLD, the mass-variable TLD can effectively reduce the structural response, especially under large external excitations. --Abstract, page iii