Studying the Large Span Multi-Cell Steel Box Girder – An Engineering Mechanics Look

Abstract Thin-walled closed steel structures are now applied widely in urban regions, especially in metropolitan or megacities. Several large span overheads, fly-overs, overpasses, and city sky bridges are built; some are horizontally curved structures for aesthetic, economic, and effective purposes. The working conditions for such structures require careful analysis, not only in the structural analysis but in the science of materials with different levels of knowledge. Stress-strain relationships in static and dynamic aspects, relating to stiffness, local and overall buckling, etc., are primary issues in engineering mechanics. Firstly, it is necessary to review the response of the thin-walled structures subjected to torsion, including equations of internal forces and moments, as well as both flexural and torsional moments of horizontally curved structures. Secondly, it focuses on studying the behavior of the thin-walled structures subjected to flexion and torsion. Finally, some in-depth investigations into warping effects are tentatively made. Some comparisons between the analytical and numerical results of normal stresses indicate a consistency of about 70% to 77% between the two solutions. Furthermore, stresses and strains at corner points of the cross-section result in distortional warping effects. Besides, by conducting a modal analysis, based on the modal participating mass, results indicate that lateral and torsional vibrations dominate in the first two modes of curved structures, as well as the straight structures. Furthermore, the sharper curvature is, that the torsional vibration appears in the first mode, disregarding the condition of supports. These contribute more to previous understandings of this special structure and unusual secondary effect _ ’warping’. The article will only focus on the superstructures in the hope of clarifying the working conditions and responses of the HCB in a general look at engineering mechanics; any infrastructure analysis is limited.