Bentley Systems, Inc. STAAD.Offshore STAAD.Offshore

Wave Load Module The wave load module calculates wave loads on structures using either stream function, Stokes 5th Order theory, AIRY theory, or a user defined grid wave. The program generates STAAD.Pro loading data for the stiffness analysis. The wave load module computes the wave loading intensities due to wave and/or current effects along the submerged portion of the structural members and appurtenances below the wave surface profile, relative to the local X, Y, Z and global X, Y, Z axes. The wave loadings are summed at the joints for each member using simple beam theory from which the total structure base shear and overturning moments are calculated. The wave can be stepped through the structure in any specified direction over a range subdivided into equal internals using either phase angles or length units. The interval is specified by giving the start and finish positions of the wave crest relative to the structure mud line axis and a step interval. The wave force co-efficients, drag, and added mass, can be specified independently for each member or using member range. The coefficients are relative to the member local co-ordinate system. Transport module The transport module can calculate the inertia forces due to motion accelerations, consisting of any combination of the 3-translational and 3-rotational degrees of freedom. The inertia loads can either be lumped at the nodes, or distributed along the members. The program generates a complete STAAD.Pro input file consisting of basic load cases for the inertia loadings on the structure, together with the STAAD.Pro commands necessary to perform analysis, output displacements, reactions, and member end forces. Motion loads can be generated in all six degrees of freedom (DOF), and combined, to form basic STAAD.Pro load cases. The DOF motions in a load case can be added or subtracted by specifying a directional load factor, such as -1.2, 1.0 and so on; a factor greater than 1.0 would signify a correction factor being applied to the generated load. If gravity tilt loads are to be generated then the global Y axis must be set vertically upwards. Also, in respect to vessel motions, a suitable axis convention would be to set the global Y axis vertical with the global X axis in the direction of the vessel longitudinal axis.