在役PC斜拉桥合龙段拆除的整体稳定性分析

Global Stability Analysis on Existing PC Cable-Stayed Bridges after Removal of its Closure Segment

合龙段置换加固技术是解决在役PC斜拉桥合龙段失效问题的新途径,而原合龙段的拆除后的全桥整体稳定性问题是不可忽视的,在合龙段拆除施工前必须进行分析并确认,以保证拆除施工的结构安全.应用结构稳定性原理,采用空间有限元分析,计算了天津永和大桥合龙段拆除前后的弹性屈曲安全系数,考虑结构几何和材料非线性,计算了全桥结构非线性稳定安全系数.非线性分析结果表明,合龙段拆除前,全桥结构具有较高的稳定性,其安全系数满足规范要求,而合龙段拆除后,全桥结构稳定安全系数有所降低,是一个比成桥更加危险的状态,采取有效措施对全桥整体稳定性予以加强是非常必要的.

When the closure segment failed in an existing prestressed concrete cable stayed bridge,the technology of replacing the closure segment was a new and effective way for this.But the global stability of the structure after removal of the old closure segment could not be ignored and must be verified before construction to ensure the structural safety.Using the theory of structural stability and FEM,the elastic buckling safety factors of Yonghe Bridge in Tianjin before and after removal of its closure segment in the middle span were calculated.Then considering its geometrical and material nonlinearity,the global stability safety factor was calculated again.Calculation results showed that, before removing the old closure segment,the global stability safety factor was big enough to meet the requirements of current bridge codes,but the factor after removing the closure segment is somewhat smaller.From the global stability point of view,the structural state after removal of the closure segment was more dangerous than the state before removal of the closure segment,and some effective measures must be taken during construction to improve the global stability.