Research On The Effect Of Damped Wind-resistant Cables On Wind-resistant Performance Of Long-span Suspension Bridges

Wind resistance of suspension bridges has always been a hot topic.Wind resistance of bridges directly affects the safety and comfort of bridges in operation.More and more long-span suspension bridges have been built in mountain canyons and tourist attractions.With the increase of span,stiffening girder stiffness becomes smaller and smaller,and the bridge is more sensitive to wind load,so the problem of wind resistance stability of bridges becomes increasingly prominent.Some suspension bridges are strengthened by wind-resistant cables,but the wind-resistant cables can not consume the energy in the bridge in time,which will lead to the wear of the connecting parts between the wind-resistant cables and the stiffening beams.Therefore,this paper studies the wind-resistant stability of bridges from the perspective of damped wind-resistant cables.In view of the shortcomings of wind-resistant cables in the wind resistance of suspension bridges,this paper analyses the variation of key mode frequencies of suspension bridges,the influence of horizontal angle of wind-resistant cables and tension force on stiffening girder stiffness,designs friction dampers,considers the reasonable arrangement of dampers and wind-resistant cables,and analyses the influence of damped wind-resistant cables on the wind resistance stability of long-span suspension bridges.The main contents of this paper are as follows:1)The influence of horizontal angle and tension force of wind-resistant cable on stiffening beam stiffness.The tension force at both ends of the windproof cable is increased from 0 MN to 1.5 MN,and the horizontal angle is increased from 0 degree to 75 degree.Modal analysis is carried out to study the frequency variation of key modes of stiffened beams.By adjusting the wind speed from 0 m/s to 70 m/s,the variation of displacement of stiffening beams under different tension forces of wind-resistant cables is studied.The analysis shows that the influence of wind-resistant cable on the natural frequency of suspension bridge is weak without tension force.The stiffness of stiffening girder is mainly enhanced by the tension force at both ends of the wind cable.Wind-resistant cables of 0 and 15 degrees have little influence on structural stiffness.With the increase of angle,the influence of wind-resistant cable on the frequency of suspension bridge vibration mode is more divergent.Wind-resistant cable increases the horizontal stiffness and vertical stiffness of stiffening beam greatly,but has little effect on torsional stiffness.Under the action of 30 degrees and 0.5 MN tension force,the wind cable has the best effect on stiffening beam stiffness.The static wind stability is calculated by applying 30 degree wind cable on both sides of the stiffening beam.With the increase of tension force,the displacement of the bridge gradually decreases.The vertical displacement of the middle point of the main cable of the original bridge decreases from 3.45 m to 2.12 m,with a decrease of 38.6%,and the torsional displacement of the stiffening beam decreases by 38%.The results show that the increase of tension force can significantly reduce the displacement of stiffened beams.2)Friction damper design and energy dissipation performance verification.According to the energy dissipation characteristics and mechanism of friction dampers,two kinds of friction dampers are designed,and their hysteresis curves and energy time history curves are analyzed respectively.When the friction factor is 0.2,the damper has good energy dissipation characteristics.3)The influence of dampers installed at both ends of wind-resistant cables on the wind-resistant stability of bridges.The influence of these variables on the key vibration modes of stiffened beams is studied by changing the friction factor,rotation angle and number of parallel connections of dampers,and the change rule of the friction factor of dampers on the displacement of stiffened beams is studied by adjusting the wind speed from 0 m/s to 70 m/s.The results show that the horizontal and vertical stiffness of stiffened beams can be increased by installing dampers on 30 degree wind cable.With the increase of the number of dampers,the frequency of the key modes of stiffened beams also increases.The change of damper angle has no obvious effect on the stiffness of the structure.When the friction factor of the damper is 0.2,the maximum horizontal displacement of the stiffened beam decreases by 5.5%,and the maximum torsion angle decreases by 22.4%.4)The influence of dampers on the wind-resistant stability of bridges at the joints of tie bars and box girders.Change the arrangement of dampers,study the change of key mode frequencies,torsion angle and horizontal displacement of stiffened beams,and adjust the wind speed from 0 m/s to 70 m/s to study the change of displacement of stiffened beams under different arrangement of dampers.The results show that the full distribution of dampers weakens the horizontal displacement of box girders and the vertical displacement of main cables more than the spacing arrangement,and has a better influence on the wind stability of bridges.When the dampers are spaced,the maximum horizontal displacement and the maximum torsion angle of the stiffened beam decrease by 34.6% and 33.5%,respectively.