Analysis of the simultaneous actions of vertical and horizontal temperature differences in transverse direction of concrete bridge box girders

Thermal or termperature differences play a crucial role in the behaviour of concrete bridge box girders. They can potentially induce significant cracks at various positions along the girders. Presently, nearly all design codes recommend considering the vertical temperature difference only. Some codes, such as EuroCode, Australia Standard and Chinese railway bridge code go a step further by requiring the inclusion of horizontal temperature difference for large concrete box girders. However, these codes typically advise treating vertical and horizontal temperature differences as separate considerations. Recent findings from in-field measurements and simulations indicate that vertical and horizontal temperature differences may act simultaneously, leading to substantial effects on the structural behavior. This paper presents the results of a study on the simultaneous effects of temperature differences and proposes combination factors to account for these concurrent actions. Analysis of temperature data from three major bridges in Vietnam over a two-year period reveals significant simultaneous temperature variations. Temperature-induced strains on bridge sections are simulated and validated against recorded data. Subsequent simulations analyze variations in thermal strain and stress. Bivariate peak over threshold analysis was conducted to predict thermal stress under extreme conditions, utilizing simulations based on field measurements and material properties.