火灾下预应力混凝土箱梁温度场研究

Study on Temperature Field of Prestressed Concrete Box Girder under Fire

摘要: 由于预应力箱梁底板受到高温作用，箱梁底面温度急剧上升并向箱室内部传导，而混凝土本身由于受沙、石、配合比等多种因素的影响的不均匀性，从而传热导致混凝土内部温度场分布不均匀，最终各材料的力学性能在不同的延火时间下出现差异。本文通过有限元软件ANSYS对混凝土、普通钢筋、预应力钢束在箱梁底板延火10 min、20 min、30 min、60 min、90 min、120 min时的温度场进行分析。最终得出随着延火时间的增加，混凝土底板出现温度分层现象，高温层厚度随距受火面由近到远逐层递减。根据预应力钢束和普通钢筋的温度随受火时间的变化，总结出不同时间的温度场变化情况及分布规律。

Abstract: Due to the high temperature effect on the bottom plate of the prestressed box girder, the temper-ature of the bottom surface of the box girder rises sharply and is conducted to the interior of the box. The concrete itself is affected by various factors such as sand, stone and mix ratio, thus transferring heat. The temperature field distribution inside the concrete is not uniform, and finally the mechanical properties of each material are different under different fire time. In this paper, the fi-nite element software ANSYS is used to analyze the temperature field of concrete, ordinary steel bars and prestressed steel beams in the box girder for 10 min, 20 min, 30 min, 60 min, 90 min and 120 min. Finally, with the increase of the extension time, the temperature stratification of the concrete floor occurs, and the thickness of the high temperature layer decreases with the distance from the fire surface to the layer. According to the temperature of the prestressed steel bundle and ordinary steel, the temperature changes with the fire time. The temperature field changes and distribution patterns at different times are summarized.