Longitudinal motion characteristics and control of a super-long-span suspension bridge under random traffic flow and wind loads
In the operational state of long-span suspension bridges,the reciprocating motion of the stiffening girder can easily lead to durability issues with the expansion joints,bearings,and dampers.Addressing the unclear longitudinal motion characteristics and control measures of the stiffening girder under complex random loading conditions for long-span highway suspension bridges,this paper takes a certain under-construction ultra-long-span suspension bridge as the engineering background.It investigates the longitudinal motion characteristics of the stiffening girder ends under the action of random traffic flow and wind loads.The study also explores the vibration reduction effects under the control of a longitudinal hybrid damping system using fluid viscous dampers and eddy current-friction compound dampers,taking into account the effects of performance degradation in both dampers.The research results indicate that during the operational state,the longitudinal motion of the girder ends is jointly caused by quasi-static motion induced by traffic and low-order longitudinal drift mode vibration induced by wind.At lower wind speeds,the longitudinal motion of the girder ends is primarily induced by quasi-static motion from traffic loads.As the wind speed increases,the wind-induced low-order longitudinal drift mode vibration gradually becomes dominant,coexisting with quasi-static motion.The longitudinal hybrid damping system effectively controls the longitudinal motion of the girder ends.However,as the maximum friction force(f)of the eddy current-friction compound damper decreases and the oil leakage percentage of the fluid viscous damper increases,the control effectiveness gradually diminishes.When the oil leakage percentage(μ)of the fluid viscous damper reaches 20%,the control effectiveness and the power dissipation ratio of the two dampers stabilize.At this point,the control effectiveness remains at a relatively high level,indicating that the longitudinal hybrid damping system has superior robustness.
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