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Brace Definition

Question:

After running the design check on a curved composite steel plate girder, the program is indicating that the girders are failing in negative flexure near the contraflexure points. The span check table and design results diagram show a very high negative moment in this region however a results table for the maximum negative moment for that same load case indicate the opposite. I don't believe that the the girders are failing in this region because it is impossible for the negative moment to be that high in the contraflexure region.
Answer:Hello,

The software performs the check for the sections based on the moments between the bracings, in the model, sent the bracing definition is not provided hence the design was performed the maximum negative moment in the bridge rather than design for a moment near contra flexure points. Thus we need to assign the transverse elements intersecting the girders at the brace locations as "brace " member type along with the "composite span information" which would enable the software to understand the bracing location and perform design checks for moments between the bracings as per AASHTO 6.10.1.6.



The modify member type option is as shown below:



In the case where there are no transverse elements intersecting the girder at the brace location, kindly create a dummy brace section and create at the brace location as shown below:


Kindly make sure these transverse dummy brace members are activated in the final construction stage.

We are attaching the modified model and the design guide for your reference. (Kindly refer Pg.24).

Kindly let us know if the problem persists.

Regards,
B Swapnil Agarwal
Technical Support Engineer

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Creation date: 3/3/2020 5:37 AM (Swapnil)      Updated: 3/3/2020 4:09 PM (Swapnil)
Files   
02_User Guide-Steel Composite Girder Design-AASHTO LRFD16.pdf
4.8 MB
DataImage12.png
105.4 KB
DataImage38.png
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DataImage42.png
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DataImage49.png
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DataImage63.png
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DataImage88.png
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midas.xlsx
559.4 KB
SUM-77-0927R All Frame Model.mcb
1.4 MB
SUM-77-0927R All Frame Model.mcb
1.4 MB
SUM-77-0927R All Frame Model.xlsx
81.5 KB
SUM-77-0927R All Frame Model[1].mcb
1.4 MB
video.webm
18.5 MB