Experimental and theoretical investigations of equivalent viscous damping of structures with TLCD for different fluids

An experimental investigation into the passive damping properties of various fluids, including magnetorheological (MR) fluid, in a tuned liquid column damper (TLCD) is undertaken. The coefficient of head loss for different fluids used in TLCDs to reduce structural responses in single-degree-of-freedom (SDOF) structures subjected to base excitation is experimentally determined. Experimental results are used to calculate the nonlinear coefficient of head loss based on a theoretical formulation. The numerical simulations of the responses of the structure-TLCD system with various fluids used in TLCDs are validated with the experimental results. Water has traditionally been used in TLCDs although semiactive control and additional functional requirements (antifreezing) of TLCDs can be achieved with MR fluids and glycol as resident TLCD liquids, respectively. The semiactive MR-TLCD works by utilizing the ability to change the damping properties (i.e., head loss) of the MR fluid by applying a magnetic field within the TLCD. However, the effectiveness of the MR-TLCD relies upon an adequate movement of the MR fluid within the TLCD (for both tuning and damping through head loss). Hence, an investigation into the passive damping properties of an MR fluid as the residing liquid within the TLCD is imperative for semiactive MR-TLCDs to be realizable. The performances of water, glycol, and a MR fluid are compared and the merits of each of the fluids in providing adequate passive damping to the structural system are discussed. The equivalent viscous damping in the structure provided by the TLCDs using each of the fluids is obtained for both harmonic and broad banded excitations. The theoretical analysis also examines if the existing TLCD theory may be implemented to accurately describe the passive damping performance of the MR-TLCD.