Optimization on vibration reduction of longitudinal constraint system in suspension bridges based on KPSO algorithm

To achieve optimization on vibration reduction of the longitudinal constraint system in the suspension bridge under the wind and traffic flow loads during operation, the Kriging-particle swarm optimization (KPSO) algorithm was constructed by integrating the Kriging surrogate model and the particle swarm optimization (PSO) algorithm with global optimization capability. Based on the existing wind-vehicle-bridge coupling vibration system, the longitudinal vibration characteristics of a large-span suspension bridge under normal wind, random traffic flow, traffic flow braking, and typhoon loads during operation were analyzed. The parameter sensitivity of the rigid central buckle and the variable parameter viscous damper to vibration reduction of the suspension bridge was analyzed. By taking the longitudinal displacement at girder end and tower top, as well as the relative longitudinal displacement at suspender cable end and girder end, as the indicators and taking the control efficiency of the cumulative value of the indicators as the goal, the vibration reduction optimization design of the longitudinal constraint system in the suspension bridge under different weight coefficients of load levels was carried out. The analysis results show that the estimation error between the sample test value and the calculated value obtained from the surrogate model is less than 5% in the case, indicating that the constructed KPSO algorithm can provide an algorithmic basis for the optimal design of the longitudinal constraint system in suspension bridges. The rigid central buckle has a significant vibration reduction control effect on the relative longitudinal displacement at suspender cable end and girder end, while the damper at girder end only has a significant vibration reduction control effect on the longitudinal displacement at girder end and the relative longitudinal displacement at cable end and girder end of suspenders near the girder end. However, it is not conducive to the longitudinal vibration reduction of short suspenders in mid span, and the relative longitudinal displacement at the short suspender cable end and girder end increases with a rising damping coefficient and decreases with a higher velocity index. The longitudinal vibration reduction efficiency of suspension bridges in descending order is as follows: rigid central buckle+damper system, only rigid central buckle system in mid span, and only damper system at girder end. Therefore, according to the principle of minimum damping force, the longitudinal constraint system of rigid central buckle+damper [1.0 MN·(m·s^-1)^-0.2] for the suspension bridge is recommended.