Study On External Prestressing Strengthening In Continuous Rigid-Frame Bridge

Large-span prestressed concrete continuous rigid-frame bridges have many advantages, and they are widely used in recent decades.Long-term experience shows that the phenomenon of different levels of girder cracking and continued excessive deflection in the middle span occur in the concrete continuous rigid-frame bridges domestic and abroad.The coupling between main girder cracking and deflection in the middle span have caused serious influence on the safety of the bridge and the use performance. Strengthened by external prestressing is one of the main reinforcement methods which used in concrete continuous rigid-frame bridges, and it is a kind of active reinforcement method; it can effectively improve the main girder bending bearing capacity, increases reserves of main girder’s compressive stress and restrain the progress of deflection in the middle span.Although the strengthened method by external prestressing has been widely applied in bridge reinforcement project, there are still many problems need to be researched deeply.In this thesis, the prestressed concrete continuous rigid-frame bridge beam cracking and the deflection in the middle span are analyzed, and combining with the engineering example qingquan temple jialing river bridgethe method of strengthened by external prestressing is studied.The bridge’s diseases, causes, the project of reinforcement and strengthening monitoring are studied.In this thesis, the main contents are:(1) discusses the present situation and existing problems of prestressed concrete continuous rigid-frame bridge domestic and abroad, as well as the significance and role of the method of strengthened by external prestressing.(2) summarizes the prestressed concrete continuous rigid frame bridge cracking and deflection in the middle span, and analyzes the main reasons.(3) expounds the system, structure and the layout of external prestressing of the strengthened by external prestressing; and the theory of calculation.(4) combined with reinforcement engineering practice, this thesis introduces the qingquan temple jialing river extra-large bridge’s disease problem, and analyzes the reasons of beam cracking and deflection in the middle span, and in the process of the reinforcement,the deflection, stress and external prestressing tensioning were monitored.(5) the overall and partial models are established by using finite element analysis software. And this thesis analyzes the effect of this reinforcement method, and studies the effectiveness of strengthened by external prestressing.