Structural effects of temperature gradient on a continuous prestressed concrete girder bridge: analysis and field measurements

The temperature of a structure exposed to the atmosphere depends on many factors such as geographical location, climatological condition, structure's orientation, materials and surface condition, and its surroundings. In this paper, the temperature distribution at a particular segment of a prestressed concrete girder bridge from the John James Audubon Bridge Project in Louisiana is quantified for different days of the year. Computed temperatures, actual observed temperature at the bridge site, and AASHTO specified gradients are presented and compared. It was found that AASHTO temperature gradient matches the measured temperature well at the site with some exceptions. The restraint moment caused by the temperature gradient was quantified and compared with the cracking moment of girder ends. Primary and secondary thermally induced stresses were then calculated for different girders. It was found that temperature gradient alone does not produce stresses that exceed the girder section's cracking limits for the investigated bridge. However, the cumulative effect of the primary thermal stresses and additional positive restraint moment due to thermal gradients and other long-term effects may well exceed the tensile strength of concrete and cause cracking.