Ultimate capacity of rectangular plates with partial depth pits under uniaxial loads

The aim of this paper is to investigate the effects of corrosion pits on the ultimate capacity of mild steel rectangular plates under uniaxial compression. For aging ship structures suffering from corrosion deterioration, the normal inspection practice is to measure the pit intensity (DOP) and maximum or average pit depth. A series of nonlinear FEM analysis on plates with partial and through thickness corrosion pits are carried out, changing geometrical attributes of both pits and plates, i.e., the radius, depth and location of pits and the slenderness of plates. The simulation results show that the volume loss dominates the degradation of the compressive capacity of pitted mild steel plates in addition to plate slenderness. This effect can be represented by the DOP and average thickness loss at pits, and the later primarily governs the collapse behavior of the plate itself. It is found that single side distributed pits have slightly severer deterioration on plates than the double sided pits with the same total thickness reduction, which tends to be more evident with increasing DOP and partial depth at pits Finally, an empirical formula based on FEM results is proposed to predict the ultimate capacity of pitted plates under in-plane compression, which can be used for practical purposes. The comparison between results from the FEM simulation and the formula shows a satisfactory fit.

► Nonlinear FEM analysis on plates with partial and through thickness corrosion pits is performed. ► The radius, depth and location of pits and the slenderness of plates are varied. ► Volume loss dominates the degradation of compressive strength in addition to plate slenderness. ► Single side distributed pits have severer deterioration than double sided pits. ► An empirical formula based on FEM results is proposed.