Study On The Long-term Deflection And The Control Method Of Prestressed Concrete Beam Bridges

In recent years, there have being more and more continuous beam bridges applied in waterway regulation project in China, which havethe characteristics of goodstructural integrity, mature construction technology, goodseismic performance, etc. But with theincrease in span and the extensionof service life, the deflection of midspan is getting worse, which makes the bridge linear irregularity, and causes safety problems to vehicle traffic. In this research, the reasons of the long-term deflection of PC continuous beam bridges are analyzed, and the methods and measures to control deflection are studied, In order to provide a reference for the future design and construction of the bridge.1) Onthe base of the descriptionof the major diseases of continuous beam bridges, the development of PC continuous beam bridges, the research status of long-time deflectionand the shortages of control methods are analyzed.2) The elements of the loss of pre-stress of PC continuous beam bridges are discussed, the influence of the value of relevant parameters topre-stressed pipe is researched. What’s more, the composition of the loss and time history of longitudinal pre-stressing are analyzed in the background of some actual bridges as well as the impact on the deflection.3)The basic theory of shrinkage and creepis elaborated, and the distinction of creep mathematical model of domestic and foreignis comparatively analyzed. The impact of the shrinkage and creep on long-term deflection is analyzed in the background of some actual bridges.4) From the point of the factors such as the loss of stiffness, changes of constant load, as well as relative humidity of the bridge structure, the influence to the long-term deflection of the bridges is analyzed.5) This investigationanalyzes the effect of controlling the long-term deflection of the bridges by increasing pre-stressing tendons in bottom slab and reducing bearing elevation of the side span, the results show, the above two methods have a significant effect to control the long-term deflection of the bridges. This researchdiscusses the measures of shrinkage and creep, construction quality and operations management to control the long-term deflection of the bridges.