Control of along-wind response of structures by mass and liquid dampers

An investigation is made of the possible application of tuned liquid column dampers and tuned liquid column/mass dampers in reducing the alongwind response of wind-sensitive structures. The structure is modeled as a lumped mass multi-degree-of-freedom system taking into account both bending and shear. The wind turbulence is mqdeled as a stochastic process that is stationary in time and nonhomogeneous in space. A random vibration analysis utilizing transfer matrix formulation is carried out to obtain response statistics. The nonlinear damping term in the fundamental equation of the tuned liquid damper is treated by an equivalent linearization technique. Numerical examples show that tuned liquid dampers, which have significant practical advantages, are as effective as the traditional tuned mass dampers if the parameters of the liquid dampers are properly selected. However, excess liquid motion in a tuned liquid column/mass damper may reduce the effectiveness of this damper. It is also shown that the wind-induced force- and acceleration- type responses of the structure with a damper, which is usually tuned to the fundamental frequency of the structure, should involve more than one vibration mode as higher-mode responses may become as large or even larger than the controlled-mode response.