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*EQUATION

Keyword type: model definition

With this option, a linear equation constraint between arbitrary displacement components at any nodes where these components are active can be imposed. The equation is assumed to be homogeneous, and all variables are to be written on the left hand side of the equation. The first variable is considered to be the dependent one, and is subsequently eliminated from the equation, i.e. the corresponding degree of freedom does not show up in the stiffness matrix. This reduces the size of the matrix. A node can only be used once as the dependent node in an equation or in a SPC.


First line:

Following lines, in a set: First line of set:

Following lines of set (maximum 12 entries per line):

Continue, giving node number, degree of freedom, value of the coefficient, etc. Repeat the above line as often as needed if there are more than four terms in the *EQUATION. Specify exactly four terms per line for each constraint, except for the last line which may have less than four terms. 

Example:

*EQUATION
3
3,2,2.3,28,1,4.05,17,1,-8.22

defines an equation of the form $ 2.3 v_3 + 4.05 u_{28} - 8.22 u_{17} = 0$, where u, v and w are the displacement for degree of freedom one, two and three, respectively.


Example files: achtel2, achtel29, achtel9, achtelcas, beamnlmpc.

next up previous contents
Next: *EXPANSION Up: Input deck format Previous: *END STEP   Contents
guido dhondt 2011-03-26