Grid Lines, Planes and Surfaces
There are three grid related modules:
- Grid lines - defining a grid of lines (typically in the global xy plane).
- Grid planes - defining flat planes (typically in the global xy plane).
- Grid surfaces - defining how grid loading should be related to grid planes.
Grid Lines
Grid lines are used to set out the basic geometry of typical building structures. The grid lines are typically aligned with global x and y axes, but can be in a user defined axis to model skewed structures. Where a circular geometry is required the grid lines can be defined as circular arcs.
Grid Planes
A grid plane is a planar surface, defined as being parallel to the xy plane of a specified axis set. (See Grid axes and the current grid above.) The orientation of the plane is determined by the axis - typically global, giving a horizontal plane; but vertical grid planes can be defined by selecting a different axis system. The location of the grid plane is then fixed by the elevation of the grid plane which defined the z coordinate of the grid plane axis at which the plane is located.
Horizontal grid planes can be identified as storeys for storey related calculations. A storey tolerance is used to define what distance above and below the plane are considered to be associated with the plane.
Grid Surfaces
Grid surfaces are used to define how grid loading will be interpreted. A grid surface is located on a grid plane and defines which elements are considered for grid loading and if these should be 1D or 2D elements. The set may be further refined by use of the element list. Only elements that both lie within the grid surface tolerance of the grid surface and are in the element list are included. The other parameters define how the load should be distributed from the grid location to the analytic elements.
Grid loading is applied to a grid surface associated with a grid planes, positioned in grid plane coordinates.
Bridge alignments are defined with respect to grid planes.