Performance of offshore concrete platforms subjected to internal explosion after gas leak

Abstract

The paper describes the assessment of existing concrete structures that support large oil platforms in the North Sea when subjected to internal explosion loads. Internal explosion loads are the result of a gas leak from the pipes inside of a hollow concrete column (shafts) supporting large concrete gravity-based oil platforms. Explosion at base, mid-height and close to the deck support of the column were studied following a gas leak at different zones of pipe networks in the shafts. Explosion models generated pressure–time curves for predicting the structural response. The structural response of the shaft during an explosion is dependent on the interaction of fluid and structure. Explosion models generated dynamic pressure–time history loading to be used in structural safety assessments. Transient dynamic analysis was carried out to assess the structural response and strength assessment was carried out using design codes. As the original designs in the past for most of the existing offshore installations did not include the ‘gas leak’ scenario, the study suggested that a suitable risk assessment for existing installations carrying utilities in the column is carried out to ensure that the structural stability is not compromised.