This study deals with the design of a bi-directional liquid damper for a SDOF structure. Two dampers are usually needed to reduce wind-induced responses of tall structures since they are along and across wind ones. The proposed damper has the advantage of controlling both responses with a single damper. The damper shows dynamic behavior of both tuned liquid column damper (TLCD) and tuned sloshing damper (TSD) in the direction of two axes perpendicular with each other. This paper presents experimental verification to confirm its control performance. First, shaking table test is carried out to investigate reducing responses of a SDOF structure by the damper. Control performance of the damper is expressed by the transfer function from shaking table accelerations to SDOF structure ones. Testing results show that the damper reduced bi-directional responses of a SDOF structure. Also, it reduced torsion responses. It was confirmed from system identification results that damping ratio of a SDOF structure increased by the bi-directional liquid damper.

In this study, nonlinear dynamic characteristics of a tuned liquid column damper (TLCD) varying with the amplitude of excitation input are evaluated through shaking table tests and numerical model of a TLCD. The tuned mass damper (TMD) analogy of a TLCD is used to simplify the formulation, in which involves equivalent viscous damping of the inherent nonlinear damping term of a TLCD. The equivalent TMD model of a TLCD shows that the dynamic behavior of a TLCD is affected by the natural frequency, the damping ratio and the ratio of total liquid mass to the mass in horizontal column of a TLCD. Shaking table test is performed to obtain experimental transfer functions that describe the dynamic behavior of a TLCD specimen subjected to a harmonic loading with various excitation amplitudes. Transfer functions for various excitation amplitudes are measured from shaking table acceleration to both the liquid displacement within a TLCD container and the control force produced by a TLCD specimen. Also, the dissipation energy due to the inherent damping of a TLCD is measured from the shaking table test varying with excitation amplitude. The variation of design parameters of a TLCD according to the excitation amplitude is investigated by comparing the transfer functions obtained from the shaking table test to those derived from the TMD analogy of a TLCD. These results showed that both the natural frequency and the mass ratio of a TLCD are independent on the variation of excitation amplitude, while the damping ratio of a TLCD increases with larger excitation amplitude.