Complex stress mechanism and design method of urban rail prestressed concrete U-beams based on finite element simulation

To explore the complex stress mechanism of prestressed concrete U-beams in urban rail transit, in order to improve the safety of urban rail transit construction and the economy of beam structures. The study first analyzed the complex stress mechanism of U-beams and obtained a tension compression rod model through finite element analysis. Then, experimental research was conducted on the vertical three-dimensional finite element stress of U-beams, and strain cloud maps were obtained and compared with calculated values. The experimental data show that the beam can still recover to its original state after the second cycle, and the beam will not crack. This recovery mechanism means that U-beams have high crack resistance and stability under complex stress processes. In the vertical deformation cloud map of the U-beam, the deflection of the mid span section is the largest, with a maximum displacement of about 20.4 mm, which is very close to the measured value of 20.3 mm. In the measured data of concrete strain measuring points and the results of finite element calculation, the difference rate between measured values and calculated values of some measuring points is within 10%. The results indicate that the U-shaped beam tension and compression rod model combined with finite element analysis has a high degree of conformity with the actual situation, and can provide technical reference for the construction of urban rail transit. The stress mechanism and design method proposed in the study have high reliability and are suitable for the design and construction of prestressed concrete U-beams in urban rail transit construction.