STAAD.Offshore - Motion/Transport Analysis (TRANSPORT)

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, e.g. -1.2, 1.0 etc., 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 of 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. This convention gives the following correspondence between each DOF in terms of ship motions as follows:

DOF Ship Motion
DX Surge
DY Heave
DZ Sway
RX Roll
RY Yaw
RZ Pitch

Thus, for example, using directional load factors it is possible to form load cases comprising of heave + roll, or heave – roll and heave + pitch, or heave – pitch, to determine the maximum member forces at all positions within a structure.

Screenshots of STAAD.Offshore in Action