Page 356 - Marine Structural Design

332 Part III Fatigue and Fracture

important. In the literature, several models are available to correct the S-N curves for the mean
stress effect. The most popular model is the so-called Modified Goodman relation that my be
expressed as (Almar-Naess, 1985):

(1 7.4)

where, Sa,N = the stress at a given fatigue life under reversed loading (mean stress is 0) and
where Sa and are the alternative stress applied and om ando, are the mean stress and
ultimate stress respectively. defined in Eq.(17.4) should be used as the stress range in the
corrected S-N curve.
17.1.5 Comparisons of S-N Curves in Design Standards
There are various kinds of fatigue design codes in the literature, e.g.:
General steel codes: BS 7608, BS 7910, Eurocode 3, NS 3472
Offshore industry: NORSOK, UK HSE (UK Den), MI, etc.
. Ship industry: classification Rules, IACS requirements
IIW (International Institute of Welding), AWS (American Welding Society).
Automobile industry, aerospace & aircraft industries, etc.
Bridges industry: BS5400 @SI, 1979), AASHTO (1989)
ASME Pressure Vessels Codes
Welded Aluminum Codes: BS8118 (BSI, 1991), ECCS (1992)

Figure 17.2 Comparison of S-N Curves for Tubular Joints (NTS, 1998)