Semi-submersible oil platforms are used in areas with harsher meteorological conditions and at depths greater than 520 meters, where the use of fixed structures is no longer practical. These Floating Production Units (FPU) are column-stabilized floating units with usually four or six major columns. They are also anchored (moored) to the seabed, which allows the translation and rotation of the structure. The columns are connected to the watertight pontoons that are submerged under the sea level. These pontoons secure enough buoyancy of the structure which keeps it afloat even in the heavy seas. Since the waterline of these structures is located along the position of the column, the small waterplane area is the first advantage of such structures due to lower wave load. Pontoons are filled with water once the unit is placed in the desired drilling location, providing enough stability. The deck of the FPU is supported on the very top of the columns by a truss structure[1]. Clearance of the deck truss allows the crew and the equipment to work and operate at the minimum wave load conditions. The deck truss consists of upper (main) deck and lower (production) deck. These decks consist of different I-profiles (bar elements), and they are connected using tubular bars. Consequently, multiple elements will cross into one specific point, creating very complicated joints in the process. These joints require specific approach of analysis where plate elements will be used to model very detailed and complicated joints, which will be shown in this thesis. Yielding analysis of two specific critical deck truss structure joints will be performed until they satisfy yielding strength criterion as described in ABS Rules.