腹板斜向开裂混凝土梁桥的剪切刚度评估方法

摘要

To study the impact of the web diagonal cracks on the shear stiffness degradation of concrete girder bridges ,a shear stiffness assessment method based on the truss model and actual diagonal crack situations was developed .From the variable angle truss model ,the ultimate shear stiffness of the concrete girder at the stirrup yielding was derived and according to the ultimate val‐ues of the shear stiffness degradation factors ,the quantitative relationship between the ultimate and elastic shear stiffness was established .The shear stiffness linear degradation model of general cracking degree was set up .When the cracking grade of a diagonal crack ascended from Grade 1 to Grade 5 ,the shear stiffness after cracking linearly descended from the elastic shear stiffness to the ultimate shear stiffness .The assessment criterion of 5 grades for the cracking degrees of the diago‐nal cracks was proposed .The practical shear stiffness assessment method for the concrete girder bridges with web diagonal cracks was worked out and the method was used to assess the web diag‐onal cracks of a prestressed concrete box girder bridge in grade and also the shear stiffness of the bridge .The results reveal that the method can well assess the shear stiffness and deflection of the concrete girder bridges with web diagonal cracks .%为研究腹板斜裂缝对混凝土梁桥剪切刚度退化的影响，提出一种基于桁架模型和实际斜裂缝状况的剪切刚度评估方法。根据变角桁架模型推导箍筋屈服时混凝土梁的极限剪切刚度，并通过剪切刚度退化因子极限值建立极限剪切刚度和弹性剪切刚度的定量关系；建立一般开裂程度下的剪切刚度线性退化模型，当斜裂缝开裂等级从1级升至5级时，开裂后剪切刚度由弹性剪切刚度线性降低至极限剪切刚度；提出斜裂缝开裂程度5级评定标准，建立实用的带斜裂缝混凝土梁桥剪切刚度评估方法。采用该方法对某斜向开裂预应力混凝土箱梁桥进行了斜裂缝分级评定与剪切刚度评估，结果表明，该方法能够较好地评价带斜裂缝桥梁的剪切刚度及下挠。