Design for Impact of Dropped Objects

The piperack and wellhead areas of the platforms in the Statfjord field have been designed for protection against accidentally dropped objects. This paper deals specifically with the design effort for the ''B'' and ''C'' platform decks. Results from three series of full scale tests are reported. Drops of 9 1/2 inch drill collars from heights ranging from 8m to 42m were performed on plate thicknesses ranging from 12mm to 47mm. Stiffened, continuously welded plates were selected for the piperack areas and areas surrounding the wellheads, while simply supported loose hatch covers were used directly above each well head. Based on information from the tests, an experimentally correlated design approach has been developed for determining necessary plate thickness for steel decks. In addition some practical recommendations for design of impact resistant deck structures are presented.