Geometric Temperature-Adaptive Assembly Control for Kilometer-Scale Cable-Stayed Bridge Steel Pylons

Addressing the core challenge of difficult alignment control caused by geometric–thermal coupling interference during the segmental assembly of kilometer-scale cable-stayed bridge steel pylons, this paper proposes a temperature-adaptive assembly method integrating the stress-free state control method and the Shape Restoration Plate (SRP). The proposed method physically blocks the load transfer path caused by temperature gradients between steel shell segments. This is achieved by installing SRP during the shop preassembly stage to temporarily lock the stress-free relative configuration of adjacent segments. On-site assembly is then performed by directly aligning the individual SRPs (segments to be assembled). Therefore, the fabrication geometry is restored with high precision, effectively decoupling the interference from temperature-induced deformations. Furthermore, based on the SRP method, an error correction mechanism is introduced to mitigate the effects of cumulative construction errors and weld shrinkage errors. Theoretical analysis demonstrates that the thermal deformation of a steel pylon in its stress-free state is reversible, with deformations autonomously dissipating on the return of ambient temperature. Validated through the project of the Guanyinsi Yangtze River Bridge (main span 1,160 m), the results show: the single-segment assembly error was reduced from 10–15 mm using traditional methods to < 10 mm (accuracy improvement ≥ 30%), segment installation efficiency increased by 25% (12 h/segment reduced to 9 h/segment), the suitable construction window expanded from 4 to 16 h per day (adapting to a temperature range of 5°C–35°C), error propagation sensitivity decreased by 50%, and overall assembly accuracy improved by 40%. This paper provides theoretical support and an engineering paradigm for the high-precision, high-efficiency, and all-weather construction of steel pylons in kilometer-scale cable-stayed bridges.