The stress range is the difference between the minimum and maximum stress resulting from the "moving" or "varying" load. It is not a function of the dead load.

Don't confuse allowable stress with the stress range listed on the S-N curve.

The allowable stress is material dependent. The S-N curve is also material dependent but would require different S-N curves for different materials such as aluminum or steel. Tensile strength or yield strength is not typically a factor in determining the useful life of a structure because the modulus of elasticity is the same for all steels within the elastic range. Likewise, the same is considered to be true for aluminum. However, the modulus of elasticity is not the same for both aluminum and steel, thus each would have a different S-N curve.

In fact, aluminum doesn't exhibit the characteristic endurance limit seen in the S-N curves for steel. Generally speaking, aluminum is going to fail sooner or later if it is cyclically loaded. One more reason why some say, “Aluminum, almost a metal.”

Al