科研之友
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摘要
In order to study the thermal effect of steel box girder and bridge deck pavement under the action of fire, a small-scale steel deck combustion experiment bench was established. The temperature data of the top surface, middle surface, and bottom surface of an asphalt pavement layer under the action of fuel fire were obtained. According to the temperature data of the top surface, a temperature-time curve based on the data of the combustion experiment was fitted and compared with ISO 834 standard temperature-time curve, and the temperature field of the small-scale experiment was verified by numerical simulation. A finite element model of a steel box girder bridge with a size of 11.25 m×3.60 m was established. The stress and deformation characteristics of the bridge under working conditions with midspan, pedestal, and full-span fire were extracted. Research results show that the temperatures in the middle and bottom of the two-dimensional numerical simulation specimens at 260.70 ℃ and 89.38 ℃ are similar to the test data at 248.9 ℃ and 82.59 ℃ under the action of the experimentally fitted temperature-time curve, and their heating trends are relatively consistent, which indicates that the temperature field simulation results are reliable. The maximum temperature drop of the steel box girder roof in the fire load area is 60.91%, which suggests that the asphalt mixture pavement layer can block the transmission of temperature to a certain extent. The maximum Mises stress on the steel box girder under working conditions with midspan and pedestal fires appears in the cold-hot alternate region where the fire load spreads to the low-temperature area. The upward deformation occurs in the fire load area under the midspan fire working condition, while the upward and downward deformations both occur in the fire load area and midspan area under the pedestal fire working condition. The Mises stress distribution under the full-span fire working condition is relatively uniform, and the downward deformation in the midspan is serious. Under the three fire modes, the stress and deformation data based on the experimentally fitted temperature-time curve are lagging behind and lower than ISO 834 standard temperature-time curve. ? 2022 Chang'an University.
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