The Stress Loss And Optimal Design In Longitudinal Prestress For Long Spans PC Continuous Rigid-Framed Bridge

With the rapid development of highway construction, more span bridges were used to span greater rivers and bays, Prestressed Concrete(PC) continuous rigid-frame bridge emerged as the times require and was developed fleetly in recent years. However, the arising problem on the inadequacy of the cross-interference in the web ramps and cracks seen deficiency of prestressed reserves in operatoring bridge bring to the people's attention. Prestressed loss affects the size of the crack resistance and the deflection of the box girder, therefore, correct analysis of prestressed loss have become an important research subject in prestressed concrete field. The prestressed design of PC rigid-frame Bridge is an important component in the optimal design, and the vertical prestressed optimization is a urgent problems need to be solved. It can be enhanced the stress performance and service life of rigid-frame bridge by appropriate prestressed design, and also can lower the costs or improve social benefits.Based on the support project of Ma Shui River Bridge on the western section of the main trunk line HuRong Road in Hubei, just around the issues with the the loss and optimization design of vertical prestressed in long span rigid-frame bridges, mainly on the following several aspect research:First, explained the basic theory and development of PC rigid-frame Bridge, introduced the major diseases about the PC rigid-frame Bridge.Secondly, combinate to the construction monitor and control technique in long span PC rigid-frame Bridge, the friction of prestressed channels and the temperature effects to the vertical prestress loss has been analysised, and the main reason for the cracking in box girder webs has been discussed.Thirdly, expounde on continuous prestressed rigid-frame Bridge theory of vertical in recent years, based on the theory of phased beam and the study of vertical prestress loss, put forward to the of vertical prestress about substitute long-beam prestressed tendons with short-beam prestressed in box girder. In order to reduce friction loss when strain tendons, and improve capacity of shearing force on the site of L / 4 box girder and increase the prestressed reserves on the root of box girder.Fourthly, both original and optimal design are adopted, according to analyze and calculate to the structure with finite element analysis software Midas / Civil to the simplified model of Ma Shui River Bridge obtain the construction phase of the stress reserves and key section internal force situation under the state of accomplish bridge, pointed out the optimal design project is scientific and rational.