Abstract This study explores how real-world temperature variations and long-term material behaviourinfluence the performance of a 45 m prestressed concrete (PSC) box-girder bridge using acoupled ANSYS-based finite element approach. Instead of relying on simplified assumptions,a transient thermal analysis was carried out to capture realistic temperature distributions,revealing clear diurnal patterns with peak top-hot conditions around 13:00 h and bottom-hotconditions around 04:30 h. The resulting temperature gradients were found to be stronglynonlinear, with a sharp thermal drop across the top slab and a more gradual variation towardsthe bottom slab. When these thermal effects were applied to the structural model, theyproduced noticeable curvature and stress redistribution. Under top-hot conditions, the bridgeexhibited an upward camber, while bottom-hot conditions induced downward curvature. Thestress analysis showed that maximum tensile stresses developed at the soffit near midspan,whereas the top slab remained predominantly in compression. Time-dependent analysisfurther revealed a progressive reduction in prestressing force, driven by creep, shrinkage, andrelaxation, leading to a measurable shift in the neutral axis and expansion of tensile zonesover time. In the long term, deflection increased significantly, with creep identified as thedominant contributor, while repeated thermal cycles further amplified deformation. Thecombined analysis demonstrated that thermal and time-dependent effects interact in anonlinear and path-dependent manner, sometimes amplifying and sometimes counteractingeach other. Overall, the results clearly indicate that soffit tensile stress at midspan governsserviceability, highlighting the limitations of conventional code-based assumptions and theneed for integrated analysis approaches for modern PSC box-girder bridges.