Allowable fatigue normal stress

Input

Number of cycles

N

Basic fatigue strength

\Delta \sigma_F

Maximum cyclic stress

\sigma_{max}

Minimum cyclic stress

\sigma_{min}

Mean cyclic stress

\sigma_{m}

Correction factor

C_R

Allowable fatigue strength

\Delta \sigma_a

Stress range

\Delta \sigma

Notes

Based on Chapter 7 "Fatigue" of the AIJ Standard for Allowable Stress Design of Steel Structures (2019): Eq. (7.1) for the allowable fatigue strength and Eq. (7.3) in 7.4 for the mean stress correction factor. Take the reference fatigue strength from Table 7.1 of the same Standard — this site carries it on the Fatigue strength (direct stress range) page.
7.1 of the same Standard does not cover the following. Ordinary buildings under cyclic stress from earthquakes and the like; low-cycle fatigue, meaning a fatigue life of 1×10⁴ cycles or fewer; corrosive environments or temperatures above 150℃; and cases where the upper or lower limit of the stress amplitude exceeds F in absolute value.
Do not include residual stress in the maximum and minimum stresses. Fatigue design works from the nominal stress on the section being designed; stress concentrations at notches and residual stress from welding are left out. That said, where a mean stress correction is applied, the maximum and minimum must be taken on values that include the stress from dead load and the like.
The cyclic stress is assumed to be of constant amplitude.
Which equation gives the correction factor depends on the stress ratio. The result field shows the one actually used.
Where the Standard writes "stress intensity", this page writes simply "stress".