Impact of Support Elevation Errors on Asynchronous Unloading of Large-Span Grid Structures

Due to construction factors, some supports of large-span grid structures may experience elevation errors. These elevation errors can adversely affect the force distribution of local members during the unloading process of the grid structure. This paper takes the unloading process of a grid structure as a case study, where two supports with significant elevation errors were unexpectedly discovered during unloading, and stress monitoring was conducted on local members. Subsequently, ABAQUS was used to calculate the modes of the grid structure and simulate the asynchronous unloading process. The dynamic effects of the step forces experienced by the lift points during asynchronous unloading were analyzed, and the causes of the stress in local members at the lift points were revealed. The results show that the numerical simulation aligns closely with the monitoring data, with the dynamic amplification effect on the structure caused by asynchronous unloading remaining within 9%. Differences in elevation between lift points exacerbate the stress on local members at the lift points. The greater the support elevation error, the more significant its impact on the stress of local members. When the error reaches a certain level, it may pose serious safety hazards to the structure. This study provides valuable guidance for the asynchronous unloading of grid structures.