Analysis of Stress Behavior at the Arch Foot of a Spatial Double-Arch Composite Steel Box Arch Bridge

To assess the structural response of the steel-concrete composite joint in a long-span half-through spatial double-arch steel box arch bridge throughout its construction and service life, a comprehensive analytical approach was implemented. Initially, a global beam-element model was constructed using Midas Civil software to determine the structural response during critical phases, including the primary construction stage (Stage 1) and operational conditions. Subsequently, a refined local finite element model focusing specifically on the arch foot's steel-concrete interface was developed in Ansys. The modeling methodology incorporated experimental validation through field instrumentation data, enabling detailed examination of both stress distribution patterns within the composite zone and the fundamental force transfer principles at this critical structural transition. Key findings from this investigation demonstrate: When subjected to the combined effects of permanent and transient loads, the shear connectors embedded in the primary arch ribs exhibit a peak Von-Mises equivalent stress of 110.8 MPa, contrasted with a minimum stress value of 5.72 MPa. Analysis of the shear connectors embedded in the primary arch ribs reveals distinct stress distribution patterns under sustained and dynamic loading conditions. The peak Von-Mises equivalent stress (110.8 MPa) manifests at location B-2, corresponding to the first-row, fourth-column position on the bottom plate. Conversely, the minimal stress concentration (5.72 MPa) is observed at position D-1, situated at the sixth-row, seventh-column intersection on the web plate. Along the direction of load transfer, the stress amplitude of shear connectors in the middle region exhibits a gradient - decreasing trend and eventually stabilizes at a certain distance from the loading point. It is noteworthy that the stress of the shear connectors at the end near the flange experiences a rebound phenomenon due to the confinement effect.