Research For Effects Of Shrinkage And Creep Of Concrete In Prestressed Concrete Hollow Slab Bridge During Widening

With a large number of low grade road was expanded into secondary highway, many old bridges were widened and continually used to save construction cost and shorten the construction period, and keep thecapacity of road in the process of construction. In a series of technical problems appearing during the widening the old bridge, such as splicing structure technology and connection mode, uneven settlemen between the foundation of old and new bridges, concrete shrinkage and creep stress on the new and old bridge structure, after the bridge was widened, the effect of new beidge on performance and bearing capacity of old bridge, they are the final key that influence the broadening quality. However, domestic and overseas are very lack of the comprehensive study of the technical problems above. At present, there are no technical specification or guidelines can be followed, therefore, it is necessary to carry out research on the key technology of highway bridge widening, it is important.This paper is an important content for the project of Yunnan province transportation hall which is named "Study on the key technology of bridge widening in low grade highway expansion project in mountain areas". The achievements in scientific research are powerful theory support to develop the design and construction guides. These results can be applied to the expansion project of low grade highway in mountainous areas. The research content mainly has following several aspects:1. On the basis of the existing research results, the expansion and analytical analysis is carried out on the shrinkage and creep effect of prestressed concrete hollow slabs which are commonly used in low grade highway in mountainous area during bridge widening, the shrinkage and creep effect formula are established.2. Prestressed concrete hollow slab bridge widening example:according to the calculation formula of creep and shrinkage effect, a20m prestressed concrete hollow slab bridge is analyzed, theoretical analysis method of a new beam concrete shrinkage and creep effect of the widening bridge.3. The deflection and stress of old and new hollow slab bridge caused by shrinkage and creep of concrete during widening is analyzed. The parameters such as new hollow slab concrete age, the slab height, the slab width, the new number of new slabs, the strength new hollow slab concrete, the environment relative humidity, the average magnitude of prestress, totally7parameters are analyzed.