钢箱梁桥面沥青混合料燃烧温度荷载与效应分析

为研究在火灾作用下钢箱梁与桥面铺装结构热效应，建立了小尺度钢桥面燃烧试验台，获取了油料火灾作用下沥青铺装层的上表面、中部和下表面温度数据；针对上表面温度数据，拟合得到了一条基于燃烧试验数据的升温曲线，与ISO 834标准升温曲线进行对比，并对小尺度试验的温度场进行了数值模拟验证；建立了11.25 m×3.60 m的钢箱梁桥有限元模型，获取了桥梁在跨中、支座附近和全跨火灾工况下的应力和变形特征。研究结果表明:在试验拟合升温曲线的作用下，二维数值模拟试件的中部温度260.70 ℃和底部温度89.38 ℃与试验数据248.90 ℃和82.59 ℃相近，且升温趋势较一致，说明温度场数值模拟结果可靠；火灾荷载作用区域钢箱梁顶板温度下降最高可达60.91%，表明沥青混合料铺装层能在一定程度上阻挡温度传递；跨中、支座火灾工况下钢箱梁最大Mises应力均出现在火荷载向低温扩散传播的冷热交替区域；跨中火灾工况在火荷载区域出现上挠变形，而支座火灾工况分别在火荷载区域和跨中区域出现上挠和下挠变形；全跨火灾Mises应力分布较均匀，跨中下挠变形严重；3种火灾模式下，基于试验拟合升温曲线的应力和变形数据均滞后且低于ISO 834标准升温曲线。 

Temperature load and effect analysis of asphalt mixture combustion on steel box girder bridge deck

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. 5 tabs, 15 figs, 30 refs.