Investigation on vertical temperature gradient of steel box girder with steel deck under solar radiation

In order to investigate an applicable vertical temperature gradient of steel box girders on steel bridge decks in China, under a weather condition of strong solar radiation and high shadow temperature, multiple field measurements were carried out to measure temperature along the vertical section of diaphragms of the cross partitions of two steel box girder bridges. The evolution of temperature on deck overlay, the diaphragm of box girder, and air inside the box girder, as well as shade temperature variation were obtained. Based on the results of the two bridges, the distribution of vertical temperature gradient along the diaphragms were analyzed and compared. It is found that high temperature difference created between the deck plate and bottom plate under solar radiation. The observed maximum temperature difference between the deck plate and bottom plate on the two bridges were respectively 16.8 ℃ and 17.2 ℃ occurred at 14:30, and the vertical temperature gradient were characterized as nonlinear feature with a turning point located 700 mm away from the deck plate. A modification to the specification of four-broken line in the Eurocode was established as to present vertical temperature gradient, with the maximum temperature between the deck plate and bottom plate of 17.2 ℃. The current results can provide good suggestion for bridges designed in China, as well as for code specifications on vertical temperature gradient of steel-deck box girder bridges. © 2021, Central South University Press. All rights reserved.