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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。
In order to give the failure criterion of prestressed concrete thin web under fire, aiming at the damage of prestressed concrete T-beam bridge under fire, the conditions of high temperature fire conduction and heat conduction mixed boundary conditions were studied. The prestressed concrete T-shaped beam , And analyze the distribution of the temperature field. The calculation details and judgment conditions of deformation and failure of prestressed concrete T-beams are also given. The thermal field coupling method was used to study the failure modes of prestressed concrete T-beams with different fire modes and to track the deformation of beam-ribs and flange plates of prestressed concrete T-beams with different fire modes. The results show that the damage time of the beam rib is the same as the failure time of the flange plate only when the beam of the prestressed concrete T-shaped beam is exposed to fire, and the fire resistance time is longer compared with other fire modes. The T-shape of prestressed concrete The cross section of the T-shaped cross-section beam produced significant distortion when subjected to unilateral fire on the lower part of the cross-section beam, and the destruction time of the T-shaped cross-section beam was earlier than that of the beam rib, When the fire, both sides of the flange plate damage are prior to the failure of the beam ribs, the destruction of time ahead of 10min; prestressed concrete T-beam roof fire or the whole subject to fire, T-section beam damage relatively early, as 40 ~ 60min, roof fire affected the fire resistance of prestressed concrete T-beams significantly. This study can provide a theoretical basis for fire resistance performance and fire-resistant design of prestressed concrete thin webs.