Ballastless Track Prestressed Concrete Continuous Rigid Frame Bridge Late Creep Deformation And Control Method

In order to guarantee the stability and safety of trains driving, the post creep deformation of high-speed railway bridges must be strictly controlled. The post creep deformation is the change of the bridge shape caused by shrinkage and creep of concrete and loss of prestress. Ronggui bridge is a prestressed concrete continuous rigid frame bridge, which the span arrangement of is (108.85+2×185+115.5) m. Taking this bridge as an example, the post creep deformation and the corresponding control methods have been researched in the paper. the follows are major work completed:1. The research status quo about shrinkage and creep of concrete was analysed. The creep theories are divided into three types, there are expressions of the creep coefficient for each type of theory. And the expressions were used in the calculation and analysis of creep deformation in Chapter IV of the paper.2. According to China highway code JTG D62—2004, the post creep deformation of Ronggui bridge has been calculated and analysed with MIDAS. The results show that the post creep deformation is a bit large, In the twentieth years after laying track, the maximum hogging of the side span is 23.1 mm, the maximum sagging of midspan is 62.7 mm. So some measures are needed to control the post creep deformation.3. The effect of three control methods, which are to delay the track time, to design post-tensioned cable and to design external cable, was analysed and compared. Many a scheme of adopting the three methods comprehensively was compared, and an effective one was suggested to control the post creep deformation.4. The influence of the time of applying secondary dead load on the post creep deformation has been studied. According to the construction sequence, the secondary dead load was divided into four kinds. Suggestions were put forword for the time of applying each kind of load.5. According to China highway code JTG D62—2004, the concrtete creep coefficient under laboratory standard state was expended into the creep coefficient which could consider the temperature change, humidity change, different forms of cross-section, different load age and so on, applied to the calculation of Ronggui bridge. By an effective control measures to post creep deformation, the post creep deformation can be limited in 5 mm, no matter hogging and sagging.The research results of this paper can provided accordance for the design and construction of Ronggui bridge, and which can also be refferenced for the design and construction of the other large span prestressed concrete continuous rigid frame bridge with ballastless track.