I need to check that the Service III stress for the bent cap is under 24 ksi.
From RC-Pier's Cap Design Report, I get the following:
CRACKING/FATIGUE CHECK:=======================Cracking check as per AASHTO LRFD (6th Edition, 2012)
...
Span 9: From 66.00 ft To 75.00 ft <------ Cracking ------> <------ Fatigue ------> Loc AbsLoc H Comb fs-t dc Srqt Sprt fs-t ratio fs-t Comb Loc AbsLoc H Comb fs-b dc Srqb Sprb fs-b ratio fs-b Comb ft ft in ksi in in in ksi ------------------------------------------------------------------------------ 0.00 66.0 42.0 8 18.1 4.1 25.2 6.8 0.0 0.00 0 0 0.0 4.3 48.0 13.5 0.0 0.00 0 1.00 67.0 42.0 8 11.6 4.1 43.9 6.8 0.0 0.00 0 0 0.0 4.0 48.0 4.6 0.0 0.00 0 2.75 68.8 42.0 8 0.5 4.1 48.0 6.6 0.0 0.00 0 1 1.7 4.0 48.0 4.4 0.0 0.00 0 6.25 72.3 42.0 0 0.0 4.1 48.0 6.6 0.0 0.00 0 1 24.8 4.0 16.6 4.4 0.0 0.00 0 6.73 72.7 42.0 0 0.0 4.1 48.0 6.6 0.0 0.00 0 1 29.1 4.0 12.9 4.4 0.0 0.00 0 8.00 74.0 42.0 0 0.0 4.1 48.0 6.8 0.0 0.00 0 1 25.1 4.0 16.3 4.6 0.0 0.00 0 9.00 75.0 42.0 1 1.0 4.1 48.0 6.8 0.0 0.00 0 0 0.0 4.3 48.0 13.5 0.0 0.00 0
I understand that the 29.1 stress is based upon the spacing required per AASHTO 5.7.3.4, but I'm not understanding where the required spacing comes from. Is the reported stress a function of the required spacing or vice versa? Is the stress reported just a limit, per AASHTO 5.7.3.4? How is RC-Pier determining the required spacing?