Auto Sizing of Members

 

Members are auto sized according to their design group

 or the whole frame auto sized at one time
. The auto size feature checks all members in a group and searches for either:

1.The lightest and then stiffest section in the same weight, or

2.The shallowest (smallest depth)

          

Members can be auto sized either elastically or plastically. In the elastic approach members are auto sized to remain within their local moment capacity, preventing the formation of any plastic hinges.

The plastic sizing approach attempts to create up to 40% over-stressing below the haunch node in the exterior columns to facilitate the formation of plastic hinges.

The auto size selection is also dependent on the specified lateral restraint. You can decide whether to have fewer restraints, giving a slightly heavier section, but less fabrication costs, or use a lighter section available but possibly more restraints required. Also,

•If an equal spacing has been specified the sections are sized to satisfy local moment capacity checks only. By defining an equal spacing, MasterPort assumes the engineer intends to adequately laterally restrain the member group in the next design step.

•If the value of equal spacing is set to zero, the sections are sized to satisfy all Axial with Moment design checks, since it is assumed that intermediate lateral restraints will not be provided.

A common section size is determined for all members in a group.