Abstract：Post‑rotation jacking is a critical construction stage for load‑path reconstruction and align ment adjustment in rotation‑constructed bridges, particularly for ultra‑wide double‑deck composite girder systems. Taking a two‑span continuous steel truss–concrete composite girderbridgewithspansof2×85mastheengineeringbackground,thisstudyinvestigates the mechanical behavior during post‑rotation jacking through theoretical derivation, finite element simulation, and on‑site monitoring. Based on the force method of structural me chanics, a linear relationship between vertical synchronousjacking force anddisplacement is derived, andananalyticalformulationforbearingreactionredistribution underlaterally asynchronous jacking is established by considering the coupling effects of verticalbending, torsion, and transverse multi‑bearing support. A full‑bridge spatial finite element model was developed in MIDAS Civil NX 2024 V1.1 to analyze the redistribution of bearing re actions and the stress response of the concrete crossbeam under different jacking condi tions. The results show that, for the investigated bridge, the jacking force–displacement response remains highly linear during synchronous jacking. The B‑axis middle bearing is more sensitive to jacking displacement than the two side bearings, with its fitted stiffness being approximately 2.19 times the average stiffness of the side bearings. Eccentric jacking causes reaction concentration at the jacked point and reaction reduction at adjacent sup ports, and the magnitude of reaction variation increases approximately linearly with jack ing displacement. When the transverse non‑uniform jacking magnitude reaches 20 mm, a tensile stress of 0.3 MPa appears at the bottom flange of the concrete crossbeam; therefore, a project‑specific stroke‑difference limit of 20 mm is recommended for this bridge, while the actual construction achieved a stroke control accuracy of ±0.5 mm and a transverse elevation difference within 1 mm. Field monitoring results validate the proposed analyti cal and numerical methods. The Pearson correlation coefficients of the measured jacking forces with the finite element and theoretical results are 0.9987 and 0.9988, respectively, and the corresponding mean relative errors are 3.84% and 4.23%. For stress responses, the measured and calculated values show a strong correlation, with a Pearson correlation coefficient of 0.9980 and a mean relative error of 12.77%; the critical mid‑span monitor ing point shows a relative error of only 0.65%. The final bridge alignment deviation is controlled within ±3 cm. The overall mean verification coefficient is 0.968, with a 95% em pirical agreement range of [0.888, 1.048], indicating that the proposed mechanical analysis framework and combined force–displacement control strategy can provide a useful refer ence for refined construction control of similar ultra‑wide double‑deck composite girder bridges with comparable span arrangement and transverse bearing layout.

Keywords: steel truss–concrete composite girder; rotation construction; system conversion; bearing jacking; mechanical analysis; finite element simulation

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