# structure ratio command

Syntax

structure ratio <keyword>

Primary keywords:

Please see Reaching Equilibrium. The ratio limit for mechanical calculations using the model solve command can be calculated in three ways, as defined by the following keywords:

average

The ratio is defined to be the average unbalanced mechanical force magnitude for all the nodes in the model divided by the average applied mechanical force magnitude for all the nodes (default).

local

The ratio is defined to be the maximum value of the ratio of the unbalanced mechanical force magnitude to the applied mechanical force magnitude for all the nodes in the model. The ratio used is scaled by 0.1 to make it mean approximately the same as average.

maximum

The ratio is defined to be the maximum unbalanced mechanical force magnitude for all the nodes in the model divided by the average applied mechanical force magnitude for all the nodes. The ratio used is scaled by 0.1 to make it mean approximately the same as average.

convergence

The ratio is defined as the maximum convergence of all the nodes in the model, with the convergence of a node defined as the local ratio divided by the target ratio. The ratio used is scaled by 1e-5 to make it mean approximately the same as average.

In increasing order of stringency, the conditions are:

average
ensures a majority of structural elements are in equilibrium.
maximum
ensures that all unbalanced forces are below a certain value, compared to average forces for the whole model.
convergence
ensures that each local unbalanced force is less than some fraction of the total forces being applied to a node. This criterion allows adjustment of the ratio-target, to allow relaxation of convergence criteria in regions specified by the user.
local
ensures that each local unbalanced force is less than some fraction of the total forces being applied to a node. This criterion can be misleading if some elements have very small stresses, because even a large ratio for one node may not be very important, given that the associated element contributes almost nothing to the overall response.