# Tolerances

## Definition​

General

The node coincidence is the tolerance within which nodes are assumed to be coincident. The grid plane is the tolerance with which entities are considered to belong to a grid plane. Elements are considered to be vertical if the element x axis is within the angle from the global z axis. This affects the interpretation of the element orientation information. Element plane is the angle within which elements are considered planar

The grid edge straightness is used when identifying panels on a grid surface (sets of elements that enclose a region) the elements will be considered to form a single edge if the change in alignment is less than this tolerance.

The grid loading edge tolerance is used if a beam or bar element is found inside the radius defined by the edge tolerance, all of the load is assumed to apply directly to that element at the closest point.

The grid plane tolerance is used to determine if entities are on a grid plane if they are within this distance of the grid plane.

(This option is only available when this dialog box is opened from the Preferences dialog box.)

The grid loading refinement tolerance is used where a grid surface is multi-way spanning in the algorithm used to distribute the load uses a number integration scheme. The grid loading refinement tolerance determines the density of the points used in the integration. Low tolerances will be adequate where a load is spread over a large number of panels and it is the behaviour of the structure is of interest. Where a single panel or a small number of panels are loaded and local effects are of interest a higher tolerance may be preferred.

Notes: The algorithm used is based on equilibrium considerations and not on satisfying the flexibility conditions, so higher tolerance levels do not necessarily give better results. A high tolerance may slow the expansion of the grid loading during the analysis.

Member Straightness Tolerance

The maximum difference of element orientation angle is the acceptable difference of the orientation angles of all the elements constitute a member. The maximum distance from the centre line is the allowable distance of deviation of the intermediate nodes of a member from the centre line. The offset distance from curved member controls the difference between the arc and the chord for curved members.

Form-finding

The bar spacer leg length is the acceptable deviation from the specified spacer leg length in form-finding analysis.

Preferred

Update the tolerances with the tolerance preferences.

(This option is not available when this dialog box is opened from the Preferences dialog box.)