Damage assessment based on modal analysis of pipe structure

The degradation of steel pipe structures, especially thickness reduction due to corrosion is a common problem found in marine structures. This calls for an evaluation of the thin structure’s structural health condition to ensure its safety and reliability. This study investigates the effect of reduction in pipe wall thickness on the pipe structure’s dynamic behaviour using the fundamental modal parameter as the indicator for its health condition. A finite element analysis utilising Abaqus software has been adapted to model the problem. The corrosion problem was simulated by thickness reduction on six damage cases. The influence of the severity and position of damage on the observed mode upon the percentage of natural frequencies’ reduction and localisation of mode shape of the pipe structure are subsequently displayed. Four mode shapes and its corresponding natural frequency were extracted from baseline model to further evaluate the sensitivity of the selected mode towards the presence of damage. The study found that severe damage in pipe structure leads to significant reduction of natural frequency and localisation of mode shape in the vicinity of damaged region. The vibration results summarised in this paper may serve as a benchmark for researchers and as a reference for design engineers.