Reaserch On The Long-Term Creep Deflection Of Prestressing Concrete Continuous Rigid Frame Bridges

With the rapid development of transportation, the long-span continuous rigid frame bridge is widely used in China. With its laconic and elegant style, comfort for driving, simply maintening, conveniently constructing and economical cost, the long-span continuous rigid frame bridge has strong competition in construction of the bridge within 250m span in our country. Although great successes have been achieved, the girder bridges built in the early period suffer different degrees of deflection at mid-span. Therefore, it is significant to study how to control the long-term deflection of the continuous rigid frame bridges.In this thesis, based on the project of the Laoshan mountain bridge, the author carries out the research of the main factors which influence the continuous rigid frame bridge's long-term deflection. Firstly, the author introduces the basic theory of concrete creep, analyzes the effect of concrete creep on the continuous rigid frame bridge's deflection and the main factors'sensitivity of concrete creep. Secondly, the author introduces the calculation methods of the prestress loss, analyzes the effect of the continuous rigid frame bridge's deflection by the prestress loss and the friction parameters. Finally, the author points out the drawback of current method for pre-camber, and gives several possible ways to control the continuous rigid frame bridge's deflection.With summarization of the research results, this thesis argues that it is essential to carry out several planed short-term tests to correct the model parameters, which make the predictive model is more consistent with the characteristics of a particular concrete creep, owing to the factors of affecting concrete creep characteristics with the complexity and universality. It is not reliable that the effect of the continuous rigid frame bridge's deflection by concrete creep only depends on the theoretical calculation, and the theoretical results must be amended on by the real-time monitoring. The author proposes that the temporary cable may be applied to control the deflection, the external prestressing technique can be utilized to reinforce a dilapidated bridge, also some new ideas described in this paper may be tried in future design.