Lifting-stress monitoring and numerical simulation of steel box girders

Due to their high load-bearing capacity and low self-weight, steel box girders are widely used in large-span bridges, making their lifting a critical construction phase. However, as span lengths increase, these structures face significant instability and deformation risks, with internal forces becoming complex and difficult to predict. Focusing on an ultra-large-span steel box girder project, this study proposes a coupled ‘monitoring–numerical simulation’ framework. Strain sensors installed at critical nodes collected real-time localised stress data, while a refined finite-element model was developed to simulate global stress and deformation responses. Results quantitatively reveal that the maximum transient stress amplitudes occurred at the lifting lugs and welding interfaces, reaching 7.28 MPa and 9.21 MPa, respectively, primarily driven by structural transformation and thermomechanical coupling effects. Furthermore, numerical simulations indicated a maximum global displacement of 8.4 mm during lifting. Cross-verification between field monitoring and numerical data confirms that all stress and deformation responses remain well below the allowable limits for Q355D steel. By establishing the ‘node-to-overall’ stress evolution laws, this methodology systematically characterises the girder’s mechanical behaviour, effectively mitigating instability risks and providing robust data-driven support for safety control in similar engineering projects.