Safety Analysis On The Passage Of Fatigue Airport Taxiway Bridge Under Moving Aircraft Load

The airport taxiway bridge is an important facility to resolve the conflict between aircraft operation and vehicle operation.It is essential to the flight safety of the airport,the safety of the ground of the aircraft,and the efficient operation of the airport.Its designed service life is about20 years.In practice,the service life is often more than ten years without any safety passing capacity test,and there are safety hazards such as cracks and dislocations between the contact parts and the plate seams.Because the on-site inspection does not have the test conditions for interrupting traffic and long-term loading,and compared with the continuous flat load of traditional highways and port bridges,the particularity of the moving load of the aircraft can cause the local load to reach six times that of the conventional bridge passing vehicle load.Above,the original inspection experience is not applicable;in addition,the special design causes it to cross the runway.On-site construction and inspection will have a great negative impact on the operation of the entire airport.Therefore,it is an effective method to use finite element simulation to simulate the safe passage capacity of taxiway bridge under fatigue state.This paper takes the taxiway bridge V2 of an airport in South China as the research object,using ultrasonic rebound method,non-linear analysis and on-site inspection and other research methods to complete the following tasks:1.Based on the principle of controlling stress distribution,the taxiway bridge entity is scaled and reduced in proportion,and the model is used as a medium to verify the theoretical calculation results,and at the same time prove the reliability of the simulation model.The taxiway bridge simulation model after parameter correction is obtained by optimizing structural parameters and material parameters;2.Use the stress-life curve to simulate the fatigue of the taxiway bridge structure,count the daily average number of vehicles,change the landing structure type,the size of the traffic load and other parameters,simulate the entire process of the taxiway bridge fatigue in 20 years,and quantify each time The cumulative effect of dynamic load on fatigue,the fatigue damage mechanism of healthy taxiway bridges is explored,and the quantitative relationship between fatigue accumulation and running times is obtained:Y=10^-10N_t²+7×10^-5N_t+Y_c,after calculation,the existing fatigued taxiway bridge can still pass 2023 aircraft,which meets the forecast requirements;3.Run the standard model on the basis of the existing fatigue taxiway bridge model,and compare the maximum deflection value and the maximum allowable deflection value of the bridge in this state,and the quantitative relationship between the maximum deflection value and the load size in the middle of the span is obtained as:Y=0.0079Q_t+Y_c,and proposed load reduction measures for taxiway bridges under fatigue conditions.The maximum operational aircraft load is 3121.33k N to ensure safe passage;4.Taking the traffic growth rate and combined aircraft models into account,predicting the safety margin of taxiway bridges,and fit the corresponding relationship:Y=0.0305α²+0.0512α+(Y_max-Y_c).According to the formula,when the average traffic growth rate of the year was 6.3066%,the aircraft just met the requirements of safe operation during the whole life cycle,so it is necessary to strictly control the traffic growth rate.The accuracy indexes of the above formulas are all greater than 99%,which provides a theoretical basis for the subsequent fatigue research of taxiway bridges;5.Considering the influence of multiple indicators,analyze the safety tolerance of the fatigue taxiway bridge,and get its calculation formula:（?）,and verify the formula with five working conditions.The results show that the formula is reliable and accurate,and it is suitable for the prediction of taxiway bridge safety clearance under fatigue condition.