The Analysis Of Downwarping And Countermeasures Of Long Span PC Continuous Rigid Frame Bridges

With the development of engineering technology, more and more large span continuous rigid frame bridge is widely used in bridge engineering of China and all over the world, but duing to some reason of the construction process and operation, now many long-span continuous rigid frame bridges appeared a variety of diseases, one of the most typical disease is girder downwarping and then it causes cracking, those seriously affect the applicability,safety and durability of the bridge normal use and its serviceable life. Although now there are a lot of research achievements,they still lack a deeper understanding, So it is necessary to do further reseaching on this subject. In this paper, the main content is as follows:1. Simply introduces the development situation and the downwarping condition of large span PC continuous rigid frame bridge, expound research theory about the causes of the present downwarping.2. Utilizing Midas Civil finite element calculation software to set up space finite element model of Shandianjiang Bridge. For the cause of downwarping, analysis related facters such as concrete shrinkage and creep, prestressing loss, cracking, overweight, folded sequence and obtain the cognition of influencing degree of the main girder downwarping.3. According to “dead load zero moment method” extended from load-balancing thought,use Shandianjiang bridge and the other two similar ones which are three span continuous rigid frame bridge to make a comparison, through prestress bending moment?self-weightbending moment value and bending moment ratio in stage of every bridge girder,abtain the characteristics that unbalanced moment affect the long-term deflection of the main girder.4) from the perspective of reducing a larger proporation of dead load in long-span PC continuous rigid frame bridge,by the characteristics of lighter quality?larger shrinkage and creep of the high strength lightweight concrete than ordinary concrete. determine the reasonable arrangement scope which is benifical to improve long-term deflection and reseach the characteristics that different arrangement scope of the high-strenth lightweight concrete affect the stress and internal force of key sections of the main grider.