In response to the continuing importance of offshore structures a framework for the simulation of offshore platforms is implemented in the open software environment E4. The non-commercial suite contains various methods for the ship design so that the newly developed procedures benefit from the existing knowledge. Jacket structures are installed as fixed platforms or compliant towers and play a significant role in the offshore exploitation. They are made out of hundreds of tubular steel members and each of the cylinders or cones can be seen as a simple body compared to ships. Besides the dynamic behaviour and fatigue analysis, the examination of the installation procedure especially the launch operation is of high interest. This article presents an analytical approach for the hydrostatic calculations of partially submerged cylinders. Hydrostatic forces on jacket structures are calculated by superimposing single cylinders and the results of the newly developed method are compared with a commercial simulation software. The aim is to speed up the computation time in comparison to numerical methods which is a significant advantage in the early design stage. The presented method will be the foundation for the simulation of jacket launching manoeuvres in time domain.