Detailed and Nonlinear Analysis for Steel Bridge Design

How we modelled and Challenges of modeling

- Bridge modelled in midas Civil
- Full 3D line element model with all construction stages, modelled as a grillage
- Tension only elements for hangers, stressed in sequence, with rigid links for connection
- Compression only supports to simulate false work during casting
- Forced displacement of supports to simulate jacking and transfer load
- Modelling of lifting girder with the bridge

Anomalies occur due to point connections
- Arch to deck connection shows peak but within the foot connection
- A common effect in most FE packages
Anomalies due to grillage
- Transverse bending induced in the longitudinal deck members
- Deck is actually a single member so the effect can’t occur

What we needed to model and How we modelled
Steel frame with complex geometry
Correct connection relationships
Temporary support condition during construction
Complex full moment connections within the steel frame for stress check
Verification of constructability

Full 3d frame model in midas Civil
Use of construction stages to control articulation of supports
Complex full moment connections modelled in midas FEA
Connections imported back into Midas Civil frame model for direct stress assessment

What we needed to model and How we modelled
Complex box steel box girder bridge
Used in two different configurations
Ground bearing
Simply supported
Models to allow for variations in loading and detailed connection requirements
Accurate plate model required for stiffness and local effects

Grillage models for bending design
Plate model for deflection analysis
Plate model for stiffener design and plate buckling
Compression only links at connections
Moving load analysis for MSV
Stress concentrations at links