大跨度PC梁式桥下挠机理分析及钢束配置

Deflection principle and prestressed steel configuration of long-span prestressed concrete beam bridges

针对悬臂施工PC梁桥施工过程中恒载和预应力的弯矩叠加过程进行了分解和对比分析,揭示了悬臂施工PC梁式桥下挠机理,并总结恒载零弯矩法在挠度控制中的不足,据此提出新的钢束配置方法.研究结果表明:新的钢束配置方法采用"大悬臂多配束,小悬臂少配束"的钢束配置形式,能保证大部分节段预应力弯矩可以抵消恒载弯矩,又能达到优于恒载零弯矩法控制跨中挠度的目的;将该法分别应用于主跨70 m刚构桥和主跨168 m连续梁桥,较原设计方案跨中挠度均明显改善.

This paper revealed the deflection mechanism of cantilever construction PC beam bridge and summarized the insufficient of zero dead load moment method in deflection control by decomposing and comparing the dead load moment and prestress moment in the process of cantilever construction stage. The new prestressed steel configuration in form of ＂large span cantilever more prestressed steels configuration, small span cantilever less prestressed steels configuration＂ can guarantee most of segments prestress moment balance the dead load moment, and it can also control the span deflection better than the dead load zero bending moment method. Compared with the results of original design method, the mid-span deflection in 70m main span rigid frame bridge and 168 m main span continuous beam bridge were significantly improved by using the new method.