飞机主起落架移动荷载作用下道基动力响应分析

Dynamic response of subgrade under moving loads of main landing gears

飞机起降过程中主起落架移动荷载引起的跑道道基土体循环动应力是导致跑道沉降和差异沉降的主要原因。采用移动荷载作用下跑道动力响应半解析有限单元法,基于叠加原理分析了B747-400和A380-800客机主起落架轮组移动荷载作用下道基土体动应力响应规律。分析结果表明：在B747-400和A380-800客机主起落架移动荷载作用下,道基浅层土体竖向正应力沿横向呈倒锅底型分布,荷载影响深度可达13 m;主起落架机轮分布对浅层道基土体竖向正应力影响较大,对深层土体影响不大;飞机移动速度对浅层道基土体竖向正应力分布影响较小,但对深层土体影响较明显,当飞机滑行速度达到60~80 m/s时,荷载影响深度达静力分析时的1.5~1.7倍;采用柔性道面板时,浅层土体竖向正应力较刚性道面结构时增加约50%,荷载影响深度增加约10%。

The cyclic dynamic stress of runway subgrade soil induced by the moving loads of the main landing gears in the process of taking off and landing is the main cause of the settlement and differential settlement of runway. Based on the superposition principle, the dynamic responses of the subgrade soil under the moving loads of the main landing gears B747-400 and A380-800 are analyzed by using the semi-analytical finite element method. The results show that under the the moving loads of main landing gears of B747-400 and A380-800, the vertical normal stress of subgrade of shallow soil is inverted as the pot type distribution, and the load influence depth can be up to 13 m. The distribution of the main loading gears has a greater influence on the vertical normal stress of shallow subgrade soil than the deep subgrade soil. The moving speed of aircrafts has an obvious effect on the distribution of the vertical normal stress of deep subgrade soil. Under the taking-off speed of 60 - 80 m/s, the load influence depth is 1.5 - 1.7 times than that of the static analysis. Compared with that of the rigid pavement, the vertical normal stress of shallow soil increases by about 50% and the load influence depth increases by about 10% for flexible panel.