I have a bridge model that is consistently telling me there are fatigue stress issues with my plate girder section.
I have exported the live load range that the model has created for a given girder and while comparing it to the section modulus at the locations reported to have issues I am coming up with a stress that is significantly less that what is reported.
When I use just the bottom fiber Sx for the areas, I compute the stress for point 42.18 as follows:
When I add in the load factor of 1.75 x 2 ksi I get the stress to be 3.52 ksi at point 42.18 for example. The fatigue report is telling me this stress is being computed for the 12 ksi allowed is 1.75 x 6.089 = 10.66 ksi. This leads to the the report of 88% of capacity being returned.
I am not sure how to reconcile these stresses, the model I have is a bridge that is skewed in excess of 20 degrees, so perhaps there is a deflection base later flange stress being considered, but the reports for this in the analysis do not return a lateral bending moment in the flange. If anyone can provide some direction it would be greatly appreciated, thank you in advance.
Please email me the file and your hand calculation so that I can test your issue.
my email is email@example.com
I sent a few files and an FTP link to the above email. I tried to send directly through the program but the size of the file was being rejected.
I got all the files and i was able to download successfuly. I shall test the file and will get back to you at the earliest.