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采用热力耦合计算方法,考虑延火方式、延火时间、钢束型式等参数,通过材料刚度高温衰变的虚拟层截面等效计算,分析了不同型式的混凝土箱梁预应力时程(沿时间变化)损失分布,研究了不同延火方式的预应力时程损失变化率,揭示了刚度高温衰变的混凝土箱梁预应力时程损失规律。结果表明:混凝土箱梁的预应力损失变化率受延火方式、延火时间和钢束型式的影响显著;随延火时间的增加,混凝土箱梁预应力时程损失呈指数型式增大;延火前期混凝土箱梁预应力时程损失增长率大,延火后期混凝土箱梁预应力时程损失增长率小,延火前期和延火后期的时间分界点为40~60min;拟合建立了混凝土箱梁预应力时程损失计算公式,公式简洁。此研究可为火灾下预应力混凝土梁桥的刚度退化及灾后评价提供依据。
By means of thermodynamic coupling calculation method, taking into account the parameters such as the delay mode, the extension time and the type of steel beam, through the equivalent calculation of the virtual layer section with high temperature decay of material stiffness, the different types of prestressed concrete box girder prestressed time history ) Loss distribution, the change rate of the prestressing time-history loss of different delay ways was studied and the law of the prestressing time-history loss of the concrete box girder with the high temperature decaying rigidity was revealed. The results show that the rate of change of prestressing loss of concrete box girder is significantly affected by the extension of flame retardation, extension of time and the shape of steel beam. The prestressing loss of concrete box girder increases exponentially with the increase of extension time. Prestressed concrete box girder prestressed time-history loss growth rate is large, post-extension concrete box girder prestressed time-history loss growth rate is small, pre-delay and post-extension period of time demarcation point is 40 ~ 60min; fitting established concrete Prestressed box girder time-loss calculation formula, the formula is simple. This study can provide the basis for the stiffness degradation and post-disaster evaluation of prestressed concrete girder bridges under fire.