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RC 3-Span Slab Bridge Fatigue Analysis following AASHTO Standard Spec Design

RC 3-Span Slab Bridge Fatigue Analysis following AASHTO Standard Spec Design

RC 3-Span Slab Bridge Fatigue Analysis following AASHTO Standard Spec Design

(OP)
I am looking for some direction on checking the fatigue for a 3-span slab bridge (40ft-50ft-40ft) that needs to be designed following the AASHTO Standard Spec since it is part of a rehab of an existing bridge. In Section 8.16.8.3 it gives the formula for the fatigue stress range that is not to be exceeded as Ff = 21-0.33*fmin+8*(r/h). It goes on to define fmin as the "algebraic minimum stress level, tension positive, compression negative in kips per square inch" but does not give any further guidance on how to determine fmin. Can anyone tell me how I actually calculate fmin? Any and all assistance would be greatly appreciated. Thanks!

RE: RC 3-Span Slab Bridge Fatigue Analysis following AASHTO Standard Spec Design

(OP)
Thank you bridgebuster for the example. So my understanding is that fmin = fs - fc, is this correct?

RE: RC 3-Span Slab Bridge Fatigue Analysis following AASHTO Standard Spec Design

you're welcome.


fmin is the sum of fatigue truck moment at the point under consideration(could be + or -) plus dead load moment, divided by Asjd. You compare that to Gamma times delta f, where delta f is your stress range divided by Asjd.

If fmin >Gamma delta f you're OK

Check you're clients requirements if the loads are factored or unfactored. I've seen it both ways.

RE: RC 3-Span Slab Bridge Fatigue Analysis following AASHTO Standard Spec Design

(OP)
This is exactly what I needed. Thanks for the information.

RE: RC 3-Span Slab Bridge Fatigue Analysis following AASHTO Standard Spec Design

You're welcome

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