English：

In order to deal with the deformation control problem of large⁃span precast beams under long⁃term load and spatial constraints, the deformation performance and bearing reliability of such componentsare systematically studied based on the Caotan parking lot project of Xi’an Metro Line 4. A deformationcalculation model considering both the time⁃varying characteristics of concrete and the cracking state ofthe section is established. The long⁃term deformation prediction under the coupling effect of concretecreep and shrinkage, the improvement of the calculation method of section stiffness under the crackingstate, the influence mechanism of spatial constraints on the stress state and bearing capacity of the beam,and the pre⁃camber setting method for coordinating the time⁃varying effects of multiple factors arestudied. The results show that the proposed long⁃term deflection calculation method can effectively predictthe coupling effect of creep and shrinkage of concrete. The calculation accuracy of beam stiffness in thecracking stage is significantly improved by combining the distribution coefficient method with Timoshenkobeam theory. The spatial constraint effect makes the beam body change from pure bending state tocompression⁃bending combined stress state, and the actual bearing capacity is significantly improved.Ignoring this effect will lead to underestimation of bearing capacity and affect the implementation ofseismic design principles. The proposed pre⁃camber setting method comprehensively considers theinfluence of time⁃varying factors, and provides a practical way for the construction control and long⁃termservice performance guarantee of long⁃span beams.