Temperature effects significantly reduce load ratings of reinforced concrete open-spandrel arch bridges, particularly when temperature drop is included in the analyses. Because of the non-linear axial force-moment (P-M) capacity interaction behavior, lower dead load factor results in a lower rating factor. For a symmetrical structure, the eccentricity (moment to axial force ratio) at every location in an arch rib due to uniform temperature changes is geometry dependent and it is an important factor affecting load ratings. The uniform temperature effect is more significant for bridges with lower rise to span ratios (flatter geometry) because the eccentricity is higher. Based on limited field measurements uniform temperature is observed only in the early morning after the heat has dispatched overnight and before the structure is subjected to solar heat. Vertical temperature gradient in the arch rib significantly depends on the exposure to the sun. The vertical temperature gradient in each rib does not appear to follow any pattern. Additional data will be needed to develop an applicable procedure to include vertical temperature gradient for open-spandrel arch bridge rating analyses.
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