中文摘要：

针对火灾下预应力混凝土T梁桥的整体刚度衰变问题，给出了结构挠变率与刚度衰变率关系方程，建立了刚度衰变与结构挠变率（挠度变化速率）耦合计算模型，利用热力耦合计算方法分析了火灾全程多梁式预应力混凝土T梁桥的结构挠变率，揭示了火灾全程多梁式预应力混凝土T梁桥刚度衰变规律。研究结果表明：T梁桥下部整体受火时，温度峰值点出现在梁肋马蹄角点处，直角点温度高于钝角点温度；火灾全程中单肋受火T梁挠变率线性递增，两肋及两肋以上受火T梁挠变率呈二次抛物线趋势递增；单侧非间隔梁肋受火的挠变率稍大于同数间隔梁肋受火的挠变率；随着延火时间的增加，多肋受火的预应力混凝土T梁整体刚度损伤呈非线性增加。火灾全程预应力混凝土T梁桥的刚度衰变研究可为预应力混凝土梁桥的灾后评价提供依据。

英文摘要：

To study the decay of rigidity for prestressed concrete （PC） bridge with T-shaped girder under fire hazard, the relation equation between variance rate of deflection and decay rate of rigidity was given out, the coupled calculation model between decay rate of rigidity and deflection variance ratio was proposed, and the thermo-dynamics coupled calculation method was adopted to analyze the variance rate of deflection for PC T-shaped girder exposed to fire. Thus, the decay law of rigidity for PC T-shaped girder exposed to fire was disclosed. The results show that the temperature peak value is located at the corner of horseshoe part and web floor. Temperature at direct corner is higher than that at obtuse corner. Deflection variance ratio of single girder has a linear increment during the entire fire process. The variance rates of deflection of two girders and multi-girders have a quadratic parabola increment during the entire fire process. The variance rate of deflection for unilateral and continuous girder exposed to fire is greater than that for the same number and interval girder exposed to fire. With increment of fire time, the whole rigidity for PC T-shaped girder has a nonlinear increment when more girders are exposed to fire. The study is sensible to assessment for prestressed concrete bridge after fire hazard. 2 tabs, 7 figs, 20 refs.