Page 465 - Marine Structural Design

Chapter 24 Random Variables and Unceriaing Analysis 44 1

Corrosion, wear and fatigue cracks, which involve “time-dependent strength”
It should be noted that all of the above involve physical uncertainties in the materials used or
in the methods of ship construction. Uncertainties may also arise from methods of calculating
structural responses, including the effect of boundary conditions, and variability in physical
behavior of materials and structures.
The subjective uncertainties required judgement and include (Mansour and Faulkner, 1974):
Shear lag and other shear effects (considered negligible).
Major discontinuities; openings, superstructures.
Torsional and distortional warping.
“Poisson’s ratio” effects, especially at transverse bulkheads and diaphragms.
Stress redistribution arising from changes in stiffness due to deformations, inelasticity, or
both.
Gross-panel compression nonlinearities; effective width,’ inelasticity, residual stresses and
shake-out effects (considered negligible).
Other subjective uncertainties not mentioned in the above are residuary strength after ultimate
strength of global panel, which may significantly affect ultimate strength and its variability.

24.6 References

1. Ang, A.H.4 and Tang, W. (1975, 1984), “Probability Concepts in Engineering Planning
and Design”, Volume I & II, John Wiley and Sons, New York.
2. Benjamin, J. and Allin Cornell, C., (1970), “Probability, Statistics and Decision for Civil
Engineers”, McGraw-Hill, Inc.
3. Mansour, A.E. (1972), “Probiblastic Design Concept in Ship Structural Safety and
Reliability”, Trans. SNAME, Vol. 80, pp. 64-97.
4. Mansour, A and Faulkner, D. (1973), “On Applying the Statistical Approach to Extreme
Sea Loads and Ship Hull Strength”, RTNA Trans., Vol. 115, pp. 277-313.
5. Mansour, A. E., et a1 (1997), “Assessment of Reliability of Ship Structures”, SSC-398.
Ship Structures Committee.
6. Melchers, R.E. (1999), “Structural Reliability Analysis and Prediction”, 2”d Edition, John
Wiley & Sons Ltd.
7. Nikolaidis, E. and Kaplan, P., (1991), “Uncertainties in Stress Analysis on Marine
Structures”, Ship Structure Committee Report SSC-363.
8. Nikolaidis, E. and Hughes, O.F., Ayyub, B.M., and White, G.J. (1993), “A Methodology
for Reliability Assessment of Ship Structures”, Ship Structures Symposium 93.
SSC/SNAME, Arlington, VA, pp H1-H10.
9. Stiansen, S.G., Mansour, A.E., Jan, H.Y. and Thayamballi, A. (1980), “Reliability
Methods in Ship Structures”, J. of RINA.
10. Thoft-Christensen, P. and Baker, M.J., (1982), “Structural Reliability, 23eory and its
Applications”, Springer-Verlag.