Research on the Optimal Design of the Flexible Suspension Bridge Suspender Based on the Failure Safety

Flexible suspension bridge refers to a suspension bridge without stiffening beams or with a small stiffening beam height. Because of its simple bridge deck structure, low steel consumption, convenient bridge deck erection and maintenance, beautiful bridge shape, and low cost, it has the characteristics of being suitable for the complex topography of the southwest mountainous area in my country. Most of the load in the flexible suspension bridge is borne by the cables. Although a certain safety factor is considered in the design, with the passage of time, under the action of the vehicle load, the bridge deck will undergo S-shaped deformation as the shape of the suspension cable changes. It is not conducive to driving safety. At the same time, the boom will be damaged due to uncertain factors such as overload and fatigue, posing a threat to the safe operation of the suspension bridge. In addition, the harsh natural environment in the mountainous area causes the fatigue life of the flexible suspension bridge to become increasingly apparent. In recent years, there have been frequent incidents of bridge collapse due to suspender breaks in our country, and the consequences cannot be ignored. Therefore, it is necessary to optimize the design of the boom of the flexible suspension bridge to ensure the safety and efficiency of the bridge.Based on the engineering example of Chelige Bridge, the paper studied the optimization design plan of damage safety the boom, and calculated the internal force of the original bridge suspension rod and the optimized boom the based on the stress difference with the aid of finite element software, and analyzed whether it could achieve the life difference. The main contents include: 1)through theoretical analysis and calculation analysis, a single boom optimization plan composed of internal and external parts proposed to replace the traditional parallel double boom, and the "damaged safety boom system" of stress difference and strength difference was evaluated. 2)A design method to achieve damage safety by changing the stress amplitude was introduced, and compared with ordinary single boom. 3)Used the full dynamic simulation method to simulate the sudden breaking of the boom, and explored the influence of the stiffness of the elastic block on the breakage of the safety boom. 4)By changing the area ratio of the inner and outer parts of the boom and the stiffness of the elastic block, the optimization effect of the safety boom with poor service life was explored.The results showed that: The optimization design plan of damage safety of the boom could not achieve a significant difference in life. On the basis of the above, a plan to add rubber pads under the safety beam was proposed, the stress amplitude was adjusted to achieve the purpose of damage safety optimization design, and the optimization effect was verified through static and dynamic analysis; finally, the section parameters and the stiffness of the rubber pads were adjusted to explore the force characteristics of the damaged safety boom. It was found that the adjustment of the section parameters had smaller effect on the force of the boom, and the change of the stiffness of the rubber pad had a significant impact on the stress amplitude of the boom.