When performing spectral fatigue analysis in SACS using the JONSWAP spectrum (JS option), two key parameters must be defined: Gamma (γ) and C. These parameters shape the wave spectrum and directly influence the resulting fatigue loading. 

If no values are entered by the user, the program applies the following defaults for JONSWAP:

• Gamma (γ): 3.3
• C: 1.525

These defaults represent the standard JONSWAP formulation commonly used in offshore applications.

When using the SCATD input line and selecting the JS (JONSWAP Spectrum) option, the Gamma and C values:

• Must be entered manually by the user if different from the defaults.
• If left blank, the program will continue using the defaults (γ = 3.3, C = 1.525).

SACS does not automatically recalculate C if the user modifies Gamma. Both values are independent input parameters.

Example

To run fatigue analysis with a Gamma value of 2.1, the user must explicitly enter the C value to be used in the analysis. If only Gamma is changed and C is left blank, SACS will still apply the default C = 1.525, not a recalculated value. Both parameters should be defined by the user if different values are intended.