This object may be used to input a connection stiffness matrix between structures using tabular input in the Matrix Definition Data window.
To add a Connection Stiffness Matrix:
Select the Connections object in the tree view.
Right-click on the Connections object and select Insert Connection > Connection Stiffness, or click on the Connection Stiffness icon in the Connections toolbar.
Select the Connection Stiffness object in the tree and enter the matrix coefficients in the Matrix Definition Data window that appears below the graphics window.
Set the Connectivity and structure information as discussed below.
The Connectivity can be set to Fixity & Structure for a structure connected to a point, or Structure & Structure for two connected structures. Select the first and second (if present) structure in the Connected Structure A and Connected Structure B fields.
The Position at Equilibrium field is available when Connectivity is set to Fixity & Structure. With Position at Equilibrium set to Geometric Position, the Response Amplitude Operators (RAOs) of the structure are calculated at the structure position as defined by the Geometry. If the Position at Equilibrium field is changed to Manual Definition, the Position X/Y/Z and Rotation About X/Y/Z fields can be used to define an alternative position for the structure RAO calculation. These options are for the purpose of calculating the structure RAOs only – the structure is not moved for the analysis.
Note:
A Connection Stiffness object only applies to a hydrodynamic diffraction analysis.
The stiffness matrix is defined with respect to the motions of the connected structure COGs.
If you want to include the effects of Linearized Morison Drag in the analysis, you cannot have two structures connected with a Connection Stiffness matrix.
Matrix Definition Data can be entered manually, can be copied and pasted from an external source (for example, an Excel spreadsheet), or can be imported from a comma-separated values (.CSV) file using the Import CSV File option. For the Import CSV File option, the file must meet the following requirements:
Has the .CSV extension.
Contains values separated by commas, tabs, or single spaces (not multiple spaces).
Contains exactly 6 columns and 6 rows.
The unit system of the data in the .CSV file is assumed to match the display unit system of the project. However, the imported data can be modified by setting the Length Unit for Imported Data, Force Unit for Imported Data, and Rotation Unit for Imported Data to the required unit system.
A connection stiffness matrix between two structures has 12 degrees of freedom. It will normally require 4 6×6 submatrices to be defined, as shown below:
where each 
is a 6×6 submatrix. Each of these matrices must be defined as described
above. The submatrices in the leading diagonal can be defined by using Fixity & Structure or
by setting the first and second structures to be the same. Only one of the off-diagonal
submatrices must be defined, as it is assumed that the overall matrix is symmetric. Defining
both off-diagonal matrices is not permitted.
If you wish to represent multiple connections to the same structure using Connection
Stiffness Matrices, the leading diagonal submatrices for that structure (the 
terms) must be summed. You cannot have multiple definitions of the same
submatrix.