Ultimate Bearing Capacity Analysis Of Exterally Prestressed Beams

The externally prestressed concrete beam is defined as a structure—unbounded tendons are used outside the concrete beams, connected with the beam by the anchorage, and deflected by the middle deflecting blocks. Lately, unbonded prestressing technology and the construction of cable-stayed bridge develop more, which settles the viability and structure design of external cables. The further applications on reinforcement of old bridges promote the development of externally prestressed concrete structure. The significant characteristic of externally prestressed concrete structure is that because the external cables are joined with beams by deflecting and anchorage equipments and the other positions are not joined with beams, the deformation of external cables and concrete is inconsistent. Should take in account the geometric non-linearity, material non-linearity and contact non-linearity between external cables and redirectors.This thesis researches analysis methods and influencing factors about the ultimate bearing capacity of the externally prestressed concrete simple beams. The tasks carried through in the thesis are listed as follows:1. Analyse the difference among externally prestressed structure, ordinary prestressed concrete structure with internal distributed steels and non-cohesive prestressed structures.2. Analyse the stress performance of the externally prestressed concrete simple beam at the ultimate situation.3. Analyse the entire process of the externally prestressed concrete simple beam from loading to destuction with single deflecting block making use of large-scale finite element sofrware-ANSYS. And contact models , coupled models, as well as consolidation models are respectively established to research the influence of connection between external tendons and the deviator to the ultimate bearing capacity. Discuss the effects of stress-strain relationship of concrete and convergence criteria to the modal calculations.4. Analyse the influence to beam behavior and the ultimate bearing capacity making use of large-scale finite element sofrware-ANSYS when the externally prestressed concrete simply supported beam is with different deviators, different effective height, different effective preload stress , different section of external cables , and ultimate strength of concrete .