Damage Assessment And Mechanical Behavior Study On Cracked Prestressed Concrete Girder Bridge

The evaluation methods for load-carrying capacity of existing bridge and research results of damage assessment on cracked concrete girder bridge at home and abroad are reviewed and summarized systematically at first in this dissertation, then the damage types of concrete girder bridge superstructure are concluded and analyzed, and the mechanical behavior and stiffness degradation laws on cracked prestressed concrete girder bridge are studied by nonlinear finite element analysis, on this basis, the qualitative and quantitative evaluation method for working performance of cracked girder according to the development degree of cracks is established which provides reference for maintenance and strengthening of existing prestressed concrete girder bridge.The main research work in this paper includes:(1) Based on the investigation on damage status and the research results of damage classification of existing concrete girder bridge, the damage types of concrete girder bridge superstructure are concluded and summarized from 3 levels as material, member and system, and the influence of various damages on service performance and load-carrying capacity is analyzed qualitatively, on this basis, the sensitive damages are presented which influence the service performance and load-carrying capacity of bridges.(2) The nonlinear finite element complete analysis under monotonic and cyclic loading is performed on prestressed concrete simply-supported T beam and continuous T beam with constant cross section, then the law of crack development, the law of girder stiffness degradation as the load increases under different development degrees of cracks, the law of girder stiffness degradation with the crack development under different load levels, and the stress change of concrete and tendon with the crack development under different load levels are studied and summarized based on different calculation models of stiffness with the fracture height as study parameter.(3) Based on the nonlinear finite element analysis results, the qualitative and quantitative evaluation method for working performance of cracked girder according to the development degree of cracks is established which provides reference for maintenance and strengthening of existing prestressed concrete girder bridge.