This paper presents a methodology to evaluate the entire process of thermal evolution and fracture failure within stay cables subjected to sheath fires. Computer software FDS 2021 and ABAQUS 2021 are applied to build a sequentially thermos–mechanics coupled method integrating thermal, structural, and fracture dynamic analyses in stay cables under sheath fire exposure conditions. Herein, three representative fire scenarios including full-circumferential, top-side, and bottom-side ignition are reconstructed. Further, 127 individual wires, accounting for interstitial cavity radiation and contact heat transfer, are utilized to perform analysis on sectional temperature in stay cables. The results indicate that the ignition mode dictates the cross-sectional temperature gradient, with localized ignitions inducing highly asymmetric thermal fields and pronounced internal bending moments. Elevated temperatures trigger a progressive load redistribution from the degraded fire-facing wires to cooler internal layers. Ultimately, abrupt global fracture occurs when the residual ultimate load-carrying capacity intersects with the actual applied tension, resulting in a fracture morphology that closely corresponds to the spatial thermal distribution. Furthermore, the structural capacity degradation exhibits three distinct time-dependent stages: a slow degradation stage, a sharp decline stage, and a recovery stage. Among the analyzed scenarios, full-circumferential ignition induces the most drastic overall capacity reduction, while bottom-side ignition poses a markedly greater rupture risk than top-side ignition.

This paper presents an investigation into the structural behavior of a suspension bridge exposed to an oil-tanker-truck fire. A coupled CFD-FEM analysis model is established to incorporate realistic oil-tanker fire scenarios and multiscale thermo-mechanical coupling, allowing the local thermal responses of critical components and global structural behavior of the suspension bridge to be captured within a unified framework. This model is validated to investigate thermal and structural responses on suspension bridges under different fire exposure lengths and locations influenced by transverse wind. Herein, this response embraces temperature rise, deflection progression, stress evolution in the main cable, force redistribution of hangers, and global failure evolution. Thereafter, failure assessment methods for main cables and hangers in suspension bridges exposed to oil-tanker-truck fires are proposed. The predominant results indicate that crosswind causes the flame to tilt toward and even fully envelop the main cable. Rapid temperature rise along the circumference of the main cable accelerates the degradation of cable load-carrying capacity, eventually leading to main cable rupture and global collapse of the suspension bridge. The proposed main-cable failure assessment method, based on fire exposure duration and surface temperature, can rapidly estimate the fire-resistance limit of main cables. Ruptured hangers lead to upward jumping of deflection in the main cable and a downward deflecting of the main girder. Force redistribution to adjacent hangers may trigger successive ruptures, and the force-based assessment method effectively evaluates the progressive collapse of a suspension bridge subjected to an oil-tanker-truck fire.