Self-Anchored Suspension Bridge - Andy Warhol Bridge (PA)

Load Rating , Project Application , Complex , Detailed Analysis , Suspension .

1 min read

Author: Aaron Colorito

Publish Date: 12 Nov, 2018






Synopsis of the Presentation

Aaron B. Colorito, Bio


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

Traditional Suspension Bridge vs Self-Anchored Suspension Bridge


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

Elevation view of the FEA model, cross section and ISO view

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:






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Speaker :  Aaron Colorito, PE, CBSI

Category : Bridge

Software : midas Civil

Date : 2016-08-03



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