To study the deformation problems of the wide and different thin-wall prestressed concrete box girders exposed to fire, the enthalpy conduction model was created. Thermal-mechanical coupled method was applied to the analysis of the deformation of the three-span wide and different thin-wall concrete box girders. Fire and load model of single span was studied. Mid-span transverse deflection of each span during prior periods and anaphase of extending-fire time was analyzed with the variation of the load ratio. The results indicate that the deflection is larger than that of other spans under the condition of fire and load of bias span, and the deflection ratio of the two-side spans is about 20～30; that the deflection of the two bias spans is downwards and the deflection of the mid-span is upward; that under the condition of fire and load of mid-span, the deflection of the three spans basically keep consistent, the deflection of the two-side spans is upward and the deflection of the two mid-span spans is downwards; that the cross-bridge effect of the side span is more obvious than that of the mid-span, and the side rib of the bias span has a upward phenomenon; and that with the increment of the load ratio, the trend of the deflection keeps unchanged, the increment amplitude of fire and load spans is larger while that of the other span is comparatively smaller.In actual engineering, load and fire of the bias span should be avoided because of the disadvantage for the deformation of the structure.%为了研究预应力混凝土宽异薄壁箱梁火场变形问题,建立了焓传导模型,利用热-力耦合方法研究了三跨宽异薄壁PC箱梁火灾高温场形变,分析了单跨受火、单跨加载模式下各跨跨中横桥向挠度随荷载比的变化规律.研究表明:边跨受火加栽模式下,两边跨下挠、中跨上挠,两边跨跨中下挠比介于20～30之间;中跨受火加载模式下,中跨下挠、两边跨上挠,三跨挠度变化量基本相等;边跨的横桥向效应较中跨的横桥向效应明显,边跨边肋在延火前期有上挠现象;随着荷载比的增加,三跨挠度变化趋势相同,受火加载边跨挠度变化量增加幅度较大,其余两垮挠度变化量增加幅度小;边跨受火加载比中跨受火加栽对结构的变形影响更为不利.
展开▼
