Project Information - Located in Pittsburgh, PA over Allegheny River - Second bridge at this site - Replaced 1884 Gustav Lindenthal suspension bridge - Mandated by 1889 River and Harbor Act - First self-anchored suspension bridge in U.S. - Constructed by American Bridge Co. and Foundation Co. of NY - First of the “Three Sisters” constructed from 1924-1928
Key Technical Issue 1: Self-Anchored Suspension Bridge (SASB) Mechanics - Need for end anchorages eliminated - Reduces right-of-way required - Girder sized for compression & flexure - Analysis by the elastic theory as an independent check - Deflection theory of suspension bridges also applicable, may be reduced to elastic theory - Special considerations for live load analysis
Overview of the Traditional vs. Self-Anchored Suspension Bridges
Key Technical Issue 2: Create Finite Element Model for SASB for various purposes A series of models are created for different purposes: - Geometry - Initial Force System - Loading & Boundary Conditions - New Dead Loads - Moving & Static Live Loads - Construction Staging (Deck Removal & Pouring Sequences) - Pedestrians-Only Load Case
FEA Modeling Process 1. The initial model is created using the Suspension Bridge Wizard of midas Civil. However, the Suspension Bridge Wizard creates the normal (externally-anchored) suspension bridge model. Therefore, further modifications were made to convert the model to be self-anchored.
2. Manual modifications are made in order to reflect the self-anchorage system. The Post-Wizard Modifications are: - Replace end boundary conditions - Insert floor system (floorbeams and stringers) - Insert rigid links at girder/chain ends - Modify Suspension Bridge Analysis Control
3. Additional Studies and FEA modeling are done for the study of the following issues: - Moving & Static Live Loads - Construction Staging (Deck Removal & Pouring Sequences) - Pedestrians-Only Load Case
Key Technical Issue 3: Results & Verification (Expectations vs. Reality)
The expectations such as below: - Elastic Theory will give larger dead load forces - Stiffening girder end moments same sign - Stiffening girder DL moments same order of magnitude
For the reality, the plan sheet forces, the elastic theory and MIDAS results are compared:
MIDAS IT has accomplished impracticable tasks, overcoming the difficult environment of the CAE industry in Korea. By using engineering simulation technology based on our own techniques through high-tech graphics, we have been developing as the biggest company that offers CAE software solution to the world.