The main cables on both sides of the tower top of super-long span suspension bridges often create significant unbalanced horizontal forces,posing considerable challenges for the design of the main towers.To suppress the frequent longitudinal micro-movements of the saddle during the operational state of super-long span suspension bridges and to reduce the stress on the bridge towers,taking a currently under-construction super-long span suspension bridge as an example,this paper proposed a self-balancing system for the main cables with dual vibration and seismic control functions.A dynamic analysis model of the bridge was established to analyze the dynamic response characteristics of the bridge under the combined action of wind and traffic loads,study the control effect of the main cable self-balancing system on longitudinal motion,and compare the longitudinal response under three structural systems of tower-cable free,tower-cable fixed,and self-balancing.The seismic and static performance of the bridge were tested and analyzed.The results show that the self-balancing system can effectively suppress the displacement of the cable saddle,and the damping rate of the peak and cumulative values of the displacement reaches 60%and 95%,respectively.The damping rate of the peak displacement of the cable saddle under the action of the E2 earthquake reaches 79%,and the ratio of the capacity demand of the tower bottom cross-section is 9 to meet the requirements of the load carrying capacity,and it improves the stress state of bridge tower to avoid the tension of concrete,which is conducive to reducing the cost.The comprehensive performance of the main cable self-balancing system is superior,which can effectively ensure the normal operation and safety durability of the bridge.
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