You're in the old LRFD Manual. The new Steel Construction Manual has Design for Fatigue located in Appendix 3. That design criteria is based on members and their connections that are subjected to repeated loading. As you probably know, no evaluation of fatigue resistance is required if the live load is less than the stress range, or if the number of cycles of application of live load is less than 20,000. Also, fatigue does not need to be considered for seismic effects or for the effects of wind loading on normal building lateral load resisting systems and building enclosure components, so, if you're calculating for any of these, the design sriteria of Appendix 3 will not apply. Calculations are shown in the new manual under 3.2, Calculation of Maximum Stresses and Stress Ranges, 3.3, Design Stress Range, 3.4, Bolts and Threaded Parts, and Table A-3-1, which shows a case by case description, and values for stress category, constant, threshold, and it also notes potential crack initiation points. The fatigue section in the new manual is much more informative and improved over the old LRFD manual.