The Application Of Pre-stressed Technology In YuDai Bridge Structure

Prestress technology has been broadly applied in the bridge construction. Since prestressed concrete structure not only has lots of advantages but also has some disadvantages, such as complex and high-quality-needed construction technology, difficult invert arch control, and difficult to densify the concrete in the pipe for the post-stressed stretching method, in order to take full advantage of the prestressed concrete structure, reasonable design and earnest construction organization are needed.This thesis takes the Jade Belt Bridge in Hefei city as an example and introduces its general picture and construction process in detail. The prestressed concrete structure design theories are summarized. After the reasonable baiting length of the prestressed steel is defined through theoretical calculation, both the stress control and extension control method are utilized to make sure the initial prestressing force of the steel could achieve the design value. Perfect proportion of the concrete are obtained; the long-term strength and additive are also used to reduce the cement amount and to cut down the number of the temperature cracks, as well as the cost of the project. Improved construction technology such as concrete placement in layers technology and double vibrating technology are used when constructing the thick area of the project, which could significantly decrease the occurrence of microcrack in the concrete. The constructing period of the project is also shortened by using one-end stretching method instead of two-end stretching method. Because of the limitation of vacuum aided mud jacking technology and plastic ripple tube, the common used mud jacking technology and metal ripple tube are used in the present project, this can also ensure the degree of the density of the concrete in the pipe, and can also decrease the cost of the project. Computations are carried out to check the local bearing area of the prestressed concrete. The cause of the crack formation in the concrete and its prevention method are also summarized. Finally, the prospect of the future development of the Prestress technology is given in the thesis.Through a comprehensive and detailed study on the construction of the Jade Belt Bridge in Hefei city, this thesis develops a series of construction technologies to help the project to achieve its goal of advanced technology, simple construction method and low cost. It was proved that these technologies could bring great economic benefits, as well as social benefits.