Residual ultimate strength of a damaged deck grillage structure

• Multi-cycle loading tests on a full-scale damaged grillage structure. • Nonlinear FEA modelling with parameterized material model. • Good agreement in nonlinear FEA predictions and test measurements. • 20.7 % reduction in ultimate strength in compression due to damage. • Modelling method applied to four previously tested undamaged grillages. A deck grillage structure was extracted from a decommissioned warship (ex-HMCS IROQUOIS) and damaged as the result of a dynamic pressure loading test, resulting in overall permanent multi-bay deformation of the plating and attached members. The damaged grillage was then re-configured for residual ultimate strength testing under longitudinal loading. The test article spanned three complete frame bays plus half-bays at each end and four continuous longitudinals of the original structure. In addition to thickness and material property measurements, Light Detection and Ranging (LiDAR) measurement of the damaged panel was carried out after re-configuration. The residual strength testing consisted of compressive loading to collapse and post-collapse, followed by two tension-compression cycles. Numerical assessments of the residual strength were performed using nonlinear finite element analysis (FEA) and material models based on measured material properties from material recovered from the ship. Excellent agreement is achieved between the measured and predicted load-shortening behaviour through progressive adjustment of the material modelling parameters. The deformation damage is estimated to result in a 20.7% loss of ultimate strength. The modelling approach developed here is then extended to the analysis of four previously-studied grillage structures recovered from the same vessel.