Spatial characteristics of temperature effects on a long-span steel box girder suspension Bridge

Temperature effects significantly influence the structural behavior of long-span suspension bridges due to their inherent flexibility and complex interactions among components. This study presents a comprehensive investigation of the spatial thermal characteristics of the Humber Bridge through integrated numerical simulations and field measurements. A two-stage analytical approach is developed. First, 2D heat-transfer analyses are conducted to determine temperature distributions in critical components (girder, main cable, suspender, and tower) under real environmental conditions. Second, a 3D structural analysis is performed to calculate thermal-induced responses by converting temperature results to thermal loads. The calculated temperatures and structural responses have a good agreement with the measurement data. Results show that the temperature-induced vertical deflection and longitudinal displacement of the girder are primarily correlated with the effective temperature, while the transverse inclination is related to the transverse temperature difference. The temperature-induced stresses of different components exhibit obvious spatial dependence: The stress of the girder varies significantly along the longitudinal direction, with a maximum daily variation of up to 36 MPa at the mid-span section; the stress of the main cable is related to the inclination of the specific cross-section, while that of the suspender is influenced by its length, inclination, and boundary conditions simultaneously. Furthermore, analyses on the influences of temperature components on temperature-induced responses show that the temperature variations in the main cable and girder dominate the structural displacements, while temperature variations in the girder primarily govern the stress responses. This study provides critical insights and advances the understanding of the spatially varying thermal behaviors of long-span suspension bridges.