Key Technology Research For External Prestressing Strengthen In Continuous Rigid-frame Bridge

Because of long-span prestressed concrete continuous rigid frame bridge’s manyadvantages, it has been constructed widely in recent years. But the continuous rigidframe bridges built at home and abroad generally appear different degree of box girdercracking and midspan deflection phenomenon. The beam’s cracking and deflectioninfluence each other, resulting in a vicious circle, seriously affected the performance ofbridge. The external prestressed reinforcement is a positive and effective activereinforcement method,it can increase the structure’s carrying capacity, improve themidspan deflection and increase the compressive stress reserves of the main beam, thismethod particularly suitable for the reinforcement of continuous rigid frame bridgewhich usually are long-span bridges. At present external prestressed reinforcementtechnology of continuous rigid frame bridge are still exist many problems and thefurther research is needed.This paper mainly focuses on the key technologies such as externally prestressedbeam’s optimized arrangement of the continuous rigid frame bridge and calculationmethods of reinforcement design, externally prestressed beam collaborative work withthe original bridge structure, and based on Amojiang Bridge’s reinforcementengineering practice, have did some detailed analysis on the key contents of bridgediseases and causes, reinforcement design scheme, reinforcement structure calculationsas well as reinforced monitoring. There mainly have done the following work:①T his paper have studied the externally prestressed beam’s arrange principle、mainly arranged shape and the layout method of long-span box girder’s externalprestressing system, Proposed a consolidated arrangement methods which is useddispose external beam combined with bottom plate of midspan section.②T he bridge carrying capacity and stress check method、whole finite elementcalculation method after reinforcement of the bridge as well as steering blocks、anchorage zone and ribs’s stress analysis.③The collaborative work mechanism of external prestressing and the originalstructure, including the formulation of external prestressing tension control stress、external prestressing loss estimation methods and stress increment and secondary effectsas well as externally prestressed beams and structural’s vibration and other issues.④According to Amojiang bridgereinforcement engineering, it has analysed the cause of the disease such as bridge midspan scratch、box girder crack and mid-spanconcrete floor crack and so on, and has checked the box girder main control section’sbearing capacity and stress of the original bridge, Proposed the reinforcement programwhich added external prestressed、bonding steel plates and added more transverse ribs.According to the calculation of the reinforcement structure before and after, we havemade the selection of the two external prestressed beam layout scheme. The externalprestressed steering blocks、anchoring structure and new mid-span transverse ribs arecarried on the local stress analysis using the finite element software.⑤The monitoring method of externally prestressed box girder stress anddeformation (deflection) of Amojiang bridge in tensioning. The research has beenapplied on the support project and the result is good.