In the process of verifying an offshore platform for a crane replacement, it was required to consider the significant deformation of several 11′ deep plate girders caused by an incident thirty years ago. The plate girders are deformed to the extent that the flanges and web are offset by over 7 inches at certain points.
A computer model was developed of the girders accounting for their curvature. Loading from the decks above, including those from the new crane to be installed, were applied to determine the existing stress in the members. Stiffeners were then designed to reduce stress levels and prevent further deformation in the future.