Abstract
When the critical wind speed of vortex-induced resonance is close to that of quasi-steady galloping, a type of coupled wind-induced vibration that is different from divergent galloping can easily occur in a rectangular bar. It is a type of “unsteady galloping” phenomenon wherein the response amplitude increases linearly with the increase in the wind speed, while a limit cycle oscillation is observed at each wind speed, whose mechanism is still in research. Mass and damping are the key parameters that affect the coupling degree and amplitude response estimation. For a set of rectangular section member models with a width-to-height ratio of 1.2, by adjusting the equivalent stiffness, equivalent mass, and damping ratio of the model system and performing comparative tests on the wind-induced vibration response of the same mass with different damping ratios, it is possible to achieve the same damping ratio with different masses and the same Scruton number with different masses and damping combinations under the same Reynolds number. The results show that the influence of the mass and damping parameters on the “unsteady galloping” amplitude response is independent, and the weight is the same in the coupling state. The Scruton number “locked interval” (12.4–30.6) can be found in the “unsteady galloping” amplitude response, and the linear slope of the dimensionless wind speed amplitude response curve does not change with the Scruton number in the “locked interval.” In addition, a “transition interval” (26.8–30.6) coexists with the “locked interval” wherein the coupling state of the wind-induced vibration is converted into the uncoupled state. The empirical formula for estimating the “unsteady galloping” response amplitude is modified and can be used to predict the amplitude within the design wind speed range of similar engineering members.
Highlights
When the critical wind speed of vortex-induced resonance is close to that of quasi-steady galloping, a type of coupled windinduced vibration that is different from divergent galloping can occur in a rectangular bar
A “transition interval” (26.8–30.6) coexists with the “locked interval” wherein the coupling state of the wind-induced vibration is converted into the uncoupled state. e empirical formula for estimating the “unsteady galloping” response amplitude is modified and can be used to predict the amplitude within the design wind speed range of similar engineering members
The wind-amplitude response curve shows a linear growth trend. ere is no vortex resonance locked interval and no divergent galloping at the single wind speed point. e pneumatic mechanism is unclear and has been called “unsteady galloping” by previous researchers
Summary
E oscillator mass is formed by the air quality, and the fluid-solid coupled shear stiffness of the vortex oscillating up and down is the vibrator stiffness For a two-dimensional (2D) cylinder, Tamura considered the influence of changes in the wake vibrator length in the vibration period He proposed a modified Birkhoff 2-DOF vortex-induced resonance mathematical model: α€ − 2ζ]1 − 4Cf2L02α2α_ + ]α − m∗Y€ − ]S∗Y_ , Y€ +2η + n f +S∗CDvY_ + Y −.
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