The serviceability/crack control check is identical for LFD and LRFD specifications. This check is only applicable to reinforce sections, and is produced for SLD (Service for LRFD) type combinations. The check is based on calculating the stress in tension steel, using a cracked section analysis, and allowable stresses from the specifications [LFD 8.16.8.4, Eq. 8-61 and LRFD 5.7.3.4, Eq. 5.7.3.4-1]. Note that if fy is 40 ksi or less, then the rebar stress is reported as 0.0, and the allowable is reported as 40 ksi.

Calculation of the steel stress (fs) is based on the procedure outlined in Caltrans Bridge Design Practice Manual [2.57.0 Working Stress Analysis Calculations].