Measurements and Structural Monitoring

Abstract

Model tests and hull monitoring can be used to measure wave‐induced hull girder loads, which are used to assess the risk of fatigue cracking and hull girder collapse. Although, the objective of model tests and hull monitoring may differ, they are valuable supplements to numerical analysis. More reliable and realistic results can be obtained, and physical aspects not covered by the idealized numerical codes can be included. Example of such is whipping and springing vibrations, which are difficult to incorporate in hydroelastic analysis. Hull monitoring is, however, not limited to hull girder loads and can include any sensor onboard covering any need. Measurements of hull girder loading are often regarded as the “truth,” but there are several uncertainties. It can be stated that the numerical analysis can never be better than the measurements, which have been used in the validation; hence, efforts should be made to limit the uncertainties in the measurements. Model tests and hull monitoring are not frequently used. Significant initial costs, lack of standardization, poor data quality, unawareness, and substandard suppliers contribute to this. The benefit during the operational life can by far exceed the costs related to model tests during the design phase or installation costs of the real vessel. Preplanned and proper data assessment is a prerequisite to bring value and decision support to the stakeholders.

Statistical Modelling and Comparison of Model-Based Fatigue Calculations and Hull Monitoring Data for Container Vessels

“…Over time, this may lead to the development of cracks which may grow and cause structural fracture, leakage and may ultimately lead to structural collapse [1]. In order to control the risk of fatigue damages, fatigue assessment of ship structures are carried out during the design phase [2], and structural monitoring may be performed during operations [3], see also [4]. By comparing fatigue rates calculated by numerical models with measured fatigue rates from hull monitoring systems, one may correct for possible biases and account for uncertainties in the numerical calculations.…”