The offshore platforms are generally designed with sufficient vertical clearance from the maximum predicted wave crest elevations. This vertical clearance is termed as 'air gap'. However, due to compelling reasons of hydrocarbon processes and also due to the increase in water levels due to climatic changes or seabed subsidence due to reservoir subsidence, the lower decks may become vulnerable to wave action due to reduction in air gap. The structural elements in the lower decks may become prone to wave-induced loads caused by high wave crests. The assessment of such wave-induced loads on the lower deck and supporting structures, especially in the existing platforms, becomes very essential for the continued safe operations. In the case of wave slamming on a structure, these supporting structural members will also be prone to large loads. Circular sections are commonly used for substructures due to their hydrodynamic efficiency; however, for deck structure, it is very common to use non-circular sections for supporting superstructure loads. The non-circular sections used in the lower decks get exposed to wave-induced loads. The imposed loads could be of higher magnitude compared with the circular sections due to the flat surface of the sections. A review of the literature indicates that the previous studies focused mainly on the circular sections and not much information is available on the non-circular shapes, especially in the case of wave slam and slap. The current study was focused on the measurement of wave-induced slam and slap loads on an array of non-circular sections in a laboratory wave flume and the estimation of force coefficient based on drag-based empirical equations. The studies revealed that the slam and slap coefficients for non-circular shapes are greater than those for circular shapes.

The offshore platforms shall be designed with deck elevation that maintains sufficient air-gap with maximum predicted wave crest elevations. However, due to compelling reasons of hydrocarbon process and changes to water levels/seabed subsidence may have structures in the close vicinity of the sea level or submerged. Hence the assessment of wave induced forces on the deck structures especially the old platforms become very essential. Review of literature indicates that the previous studies focused mainly on the circular sections and not much information is available on the non-circular sections. The current study focused on measurement of wave induced slam/slap loads in a laboratory wave flume and estimation of force coefficients based on drag based empirical equations. Further, it is of interest to focus on the flow around the open sections (non-circular) using a flow visualization technique (Particle Image Velocimetry) to understand the flow pattern around the elements. The results indicate that the slam and slap coefficients for I sections are smaller than the channel sections and the values of coefficients are few times higher than the circular sections.