Compartment level progressive collapse strength as a method for analysing damaged steel box girders

• Rapid assessment of damaged steel structures improves safety and chance of recovery.
• Α method to analyse these structures has been developed and its accuracy assessed.
• A compartment’s ultimate collapse strength is compared to models at smaller scales.
• Τhe method can model the reduced strength in cases where the failure mode changes.
• Results show good, but conservative, prediction of the ultimate bending strength.

It is vital to be able to rapidly assess damaged ship structures. This ensures the safety of personnel and facilitation of the most effective repair or recovery. Interframe progressive collapse analysis has been used as a method for rapid assessment for vessels but its suitability for application to damaged vessels has been questioned, due to the limited failure modes assessed and modelling assumptions required when implementing the method. To reduce the cost and increase the effectiveness of the recovery of a damaged vessel, it will be important to more accurately assess the structure by determining the correct failure mode. This paper presents a study on the use of progressive collapse analysis to model damaged box girders which assesses the structure across multiple frame boundaries. The study shows that while progressive collapse analysis can be applied in the assessment of damaged box girders, implementing the newly proposed assessment allows greater accuracy in the calculation of the collapse strength through capture of the true mode of failure. This new method will allow the effects of the damage on surrounding structure to be captured which can influence the deflection shapes that will lead to collapse of the structure.