Analysis and Design of Steel a Floating Pontoon Jetty for Use in the Coastal Waters of Nigeria

Floating pontoons are semi-permanently moored structures on a water body to provide boarding access to commuters. The decision to develop such structures was informed by the need to provide berthing access to river crafts that operate on the coastal waters of Bayelsa State, Nigeria. In this project, a floating pontoon, a gangway, and other supporting structures like scantlings and spud pillars, were designed to meet the needs and environmental requirements of the area. Standards consulted are the DNV Rules for the classification of ships; DNV Rules for the classification of Floating Docks; ABS Rules for Building and Classing Steel Barges; and other relevant Nigeria and Imo standards. The pontoon designed has dimensions: 13 x 12 x 4.8 m; gross tonnage of 15 tonnes; 2nos. of dry tanks of capacity 17.2 m³ and 6nos. of manholes of 450 x 550 mm. The strength of materials analysis was limited to the floating pontoon for limitations of space for this paper. The pontoon and scantling design has been done based on the worst condition of design pressure which is for the maximum submersion draft. Normal grade steel of yield strength 235 MPa is chosen for all members except the pontoon girders, frames and pillars. This is to reduce the material scantlings and to ensure higher strength with lesser scantlings. Longitudinal framing is adopted in the pontoons as the pontoon structure needs more strength in the longitudinal direction.