中文摘要：

为分析开裂预应力混凝土箱形桥梁结构开裂后的残余承载力，以裂缝统计特征参数为基础，用单元退化方式模拟正裂缝，用裂缝间的单向受压杆模拟裂缝间的承压效应，采用空间梁单元和三维杆单元分别模拟梁和预应力筋，以单元降温的方式模拟预加力的效应，形成空间刚架模型模拟斜裂缝。基于开裂后混凝土及预应力钢筋的基本假定，建立开裂后结构的计算方法。按照相似高度、开裂区域截面折减、折减自重补偿的原则将相似裂缝进行合并处理，得到裂缝区域的阶梯型折减刚度模型，提出承载能力折减系数计算方法以体现开裂后结构刚度的变化。经实桥算例验证，本文方法可正确判断静定及超静定预应力混凝土结构开裂后承载力的变化程度。

英文摘要：

Based on the crack statistic characteristic parameters, the unit degradation mode was utilized to simu- late the fracture of prestressed concrete box bridges and analyze its residual bearing capacity. In the meantime, unidirectional compressive rod, space beam clement and cooling unit form were adopted to simulate the effects of pressure among cracks, prestressed tendons and the pre - tension effect, in order to form a space rigid frame model. Based on some basic assumptions of cracked concrete and prestressed steel, the calculation method was established after cracking. Merging similar cracks by the principle of similar height, reduction of cracking area and reduction gravity compensation, the ladder - type stiffness degradation model of crack area was then estab- lished and a capacity reduction calculation method was proposed to reflect the change of the crack stiffness. The real bridge example proves that the method can correctly judge the change of bearing capacity for cracked static determinacy and indeterminacy concrete structures.