Collapse analysis of externally prestressed structures (PDF)

Inhaltsangabe:Introduction:
This dissertation is an investigation into the behaviour of externally prestressed structures, focusing on bridge box girders, at the ultimate limit state. The main objective is the ductility and the tendon stress increase up to failure of externally prestressed structures. Their behaviour will be compared to internally prestressed structures. The dissertation may have valuable information for the first stages of the design process for medium span bridges as the study is concerned about the overall safety and efficiency of prestressed concrete bridges by the means of ductility. The aim is also to provide information about the tendon stress at failure, which is required for the detailed design. Inhaltsverzeichnis:Inhaltsverzeichnis:
AcknowledgementsVIII
NotationIX
1.Introduction1
1.1Definitions1
1.2Significance of this study3
1.3Scope of the project5
1.4Historical overview and typical characteristics of external prestressing6
1.5Further structural applications of external prestressing9
2.Behaviour of externally prestressed structures10
2.1Tendon layout considerations10
2.2Behaviour at serviceability stage12
2.3Fatigue problems14
2.4Behaviour at ultimate limit stage14
2.4.1Influence of tendon slip on the ultimate limit state18
2.4.2Influence of the arrangement of the deviators on the behaviour at ultimate limit state19
2.4.3Influence of simply support and continuous support on the ultimate limit state20
2.4.4Precast segmental and monolithic bridges21
3.Collapse analysis23
3.1Investigated bridge types and their differences23
3.2Original bridge data28
3.3Simplified bridge data as basis for the calculations30
3.4FE Calculation32
3.4.1Technical aspects33
3.4.2General approach34
3.4.3Geometric model39
3.4.4Element specifications40
3.4.5Constitutive models45
3.4.6Ordinary reinforcement59
3.4.7Prestress60
3.4.8Material and geometric non-linearity63
3.4.9Kinematic constraints66
3.4.10Discrete crack propagation analysis of the precast segmental type with gap elements68
3.4.11Summary of the dividing features of the different structure types for the FE analysis72
4.Results73
4.1Load deflection behaviour73
4.2Tendon stress increase up to failure76
4.3Other results78
5.Discussion of the results85
5.1Interpretation of the results85
5.2Discussion of the exactness of the FE calculations by comparing to the full scale test89
5.3Comparison to other FE calculations and test results93
6.Conclusion and [...]