PSI - Issue 45

Mark Mogeke et al. / Procedia Structural Integrity 45 (2023) 36–43 Author name / Structural Integrity Procedia 00 (2019) 000 – 000

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assume a constant value of n (for example, cosine squared function) when applying wave spreading to the stress calculations.

Table 3. The Kendall correlation ( τ ) and P-value at SG-2 and SG-3. σ RMS χ H s T z

θ

n

τ SG-2 τ SG-3

1 1 1 1

0.26 0.45

0.85 0.72

-0.30 -0.27

0.064

-0.033

0.13 0.02

-0.05 0.23 0.06

p-value SG-2 p-value SG-3

<0.001 <0.001

0

<0.001 <0.001

<0.001

<0.001

Fig. 3. Measured vs Computed RMS stress for short-crested seas comparing different wave environment data sources.

The current investigation does not include fatigue analysis. This is mainly due to the large number of uncertainties related to fatigue predictions. Even if relatively good agreement between calculated and measured stresses is achieved, there can be poor agreement between the associated fatigue damage values, because the fatigue life of the aluminium welded joints is a function of approximately the fourth power of the stress range (Magoga et al., 2016). However, fatigue analysis is part of future work. Though there are many uncertainties related to fatigue predictions, VHM can serve as a valuable tool for estimating the service or maintenance needs of a ship and be a ‘value - add’ for ship owners and classification societies. 5. Conclusion Rigorous assessment of the safety and performance of a ship and efficient management of the hull structure requires knowledge of the hydrodynamics and structural responses to the encountered wave conditions. Methods to gain this knowledge are often limited to speed and significant wave height thresholds, and do not consider the sensitivity of the ship responses to wave energy at particular frequencies. Instrumented hull monitoring (IHM) can fill this knowledge