1. AASHTOWare Bridge Rating – Curved Girder Module
Vanessa Storlie, E.I.T.
Chad Clancy, P.E.

2. Presentation Organization
Background Info
Modeling
Analysis
Results
Conclusions

3. Background Info
Performed Beta Testing of Curved Girder Module in BrR 6.5
Needed to use a bridge where design force effects and resistances were available
Bridge had to be curved but with a small enough radius where the curvature would have an effect
Selected a four-span continuous unit with a radius of feet; four girders in cross-section spaced at 10’-4”; bridge was designed by MM

4. Modeling – General Information
Appurtenances (medians, parapets, railings, etc.) do not have to be input as “generic” as shown in example.
Define different diaphragm/cross-frame types using “Diaphragm Definitions”

5. Modeling – Superstructure Definition – Definition Tab
On Superstructure Definition window, the rating engineer must input the design data for the curve along the superstructure reference line.

6. Modeling – Superstructure Definition – Analysis Tab
On the Analysis Tab of the Superstructure Definition window, the user can set the number of shell elements to be used either in the deck between girders or in the web between flanges. The user can also set the target aspect ratio for the shell elements.

7. Modeling – Structure Framing Plan Details
The “Structure Framing Plan Details” window has additional input for the curved girders. The default bearing alignment is required as well as the distance from the superstructure reference line to the leftmost girder. Table of girder radii can be used to verify that the information is correct.

8. Modeling – Structure Framing Plan - Diaphragms
Assign cross-frame/diaphragm at each brace point.

9. Modeling – Structure Framing Plan Schematic

10. Modeling – Diaphragm Loading Selection
Check the boxes for which you want force effects to be calculated
Adds a significant amount of time to the analysis.

11. Modeling – Member Alternatives
Curved girders input the same way as straight girders.
Girder web does not have to be defined with separate sections for each different cross-section
For bearings aligned along a chord line, angles should be closer to zero than to 90.
Local z-axis is transverse and y-axis is vertical

12. Modeling – Visual Verification of Input
Traditional framing plan, cross-section, and girder schematics are still available.
3D schematics showing elements are available when using 3D FEA analysis

13. Analysis – Analysis Settings
Need to set “Analysis Type” to 3D FEM. Everything else remains the same to previous versions. Analysis time for this bridge was between two and four hours depending on the computer (must use 64 bit to analyze curved girders, 32 bit runs out of memory); force effects in diaphragms were not determined.

14. Results
Dead load and live load moments and shears can be obtained from “View Analysis Report”; element level forces/stresses can be found in xml files by using “View analysis output”
Report tools function but it appears as though there are small bugs in populating the reports for both LFR and LRFR.

15. Results
Compared BrR moments and shears to BSDI values used for design. Generally very similar for interior girders, some differences for exterior girders that with additional effort could be eliminated.

16. Conclusions
BrR provides moments and shears similar to those from BSDI analysis used for design.
Some significant differences in positive moments – reason yet to be identified
Need to look at cross frames
More comparisons planned as part of rating 5-span units on the Huey P. Long bridge in New Orleans