中文摘要：

为了给出火灾下预应力混凝土薄腹梁的破坏准则,针对火灾下预应力混凝土T形截面梁桥的破坏问题,研究火灾高温传导模式和热传导混合边界条件,设定预应力混凝土T形截面梁的火灾作用模式,分析其温度场分布状态,并给出预应力混凝土T形截面梁变形破坏的计算细节和判定条件。采用热力场耦合计算方法,研究不同火灾模式下预应力混凝土T形截面梁桥的破坏模式,跟踪不同火灾模式下预应力混凝土T形截面梁的梁肋变形和翼缘板变形路径。研究结果表明：仅预应力混凝土T形截面梁的梁肋受火时,梁肋的破坏时间和翼缘板的破坏时间相同,其耐火时间相对于其他受火模式较长;预应力混凝土T形截面梁下部单侧受火时,T形截面梁的截面产生显著畸变,受火侧翼缘板的破坏先于梁肋的破坏,破坏时间提前10min;预应力混凝土T形截面梁下部和顶部均受火时,两侧翼缘板的破坏均先于梁肋的破坏,破坏时间提前10min;预应力混凝土T形截面梁顶板受火或整体受火时,T形截面梁的破坏时间相对较早,为40～60min,顶板受火对预应力混凝土T形截面梁的耐火极限影响显著,该研究可为预应力混凝土薄腹梁的抗火性能研究和抗火设计提供理论依据。

英文摘要：

To provide failure criterion of prestressed concrete thin-web grider exposed to fire,aimed at the failure problem of prestressed concrete T girder exposed to fire,the heat transfer model and the combined boundary condition of thermal conduction were investigated,the fire exposure model of prestressed concrete T girder was set,the temperature distribution in girder section of prestressed concrete T girder was analyzed,and the calculation detail and the decision condition of deformation damage in prestressed concrete T girder were proposed.The thermomechanical coupling method was applied,to investigate the failure model of prestressed concrete T girder exposed to fire,and trace the deformation path of rib and flange plate in prestressed concrete T girder under different fire models.The results show that when the rib is only exposedto fire,the failure time of rib and flange plate is identical,and fire-resistance time is relatively longer than other fire models.When the single side under prestressed concrete T girder is exposed to fire,there is obvious distortion of T grider.The damage of flange plate exposed to fire is prior to the damage of rib,about 10 min in advance.When the top of the flange plate and the bottom of T girder are all exposed to fire,the failure time of bilateral flange plates is 10 min earlier than that of rib.When the top of the flange plate or the girder is exposed to fire,the failure time of T girder is relatively earlier than that of other fire models,between 40 min and 60 min,and the top of flange plate exposed to fire has an obvious influence on fire resistance of prestressed concrete T girder.This research may provide a theoretical basis for fire resistance performance research and design of prestressed concrete thin-web girder.