Crossarms have a number of parameters that can be configured to model a variety of different types of cross arms.
Material
Crossarms have four material types that can be selected:
wood,
steel,
concrete, and
composite.
The material type will determine which strength reduction factor is applied based on how the environment are configured.
For example if the cross arm is set up as wood and the environments tab has a strength reduction factor of 0.3 set up for serviceability (everyday loading) then the strength of the cross arm will be derated by multiplying the ultimate strength by 0.3.
Usage
This will change the rendering of the beam to either look like a cross arm or an insulator.
Shape Type
There are three option here which are Rectangular, Tubular and Flanged.
Rectangular
Rectangular means that the cross arm is a rectangular solid beam.
Width and Depth
The length, width and depth of a cross arm is defined as per the diagram below.
Note that the selection of depth and width will determine how the cross arm will handle vertical and longitudinal loads under FEA simulations which is explained in Second Moment of Area vs Horizontal/Vertical and Section Modulus vs Horizontal/Vertical
Currently there is no way to rotate a cross arm 90 degrees in Neara and hence to model a rectangular cross arm that can be installed in either direction, two cross arms would need to be set up (one with larger dimension in the depth and other larger dimension in the width).
Tubular
Tube Type
The following tube types are available Round, 4F Square, 4F Rect, 6F, 8F, 12F or 16F. Note the UI will look slightly different for tubular cross arms depending on the Tube Type selected.
Diameter (Tube Type: Round)
This is the outside diameter of the round tubular crossarm.
Width (Tube Type: 4F Square)
This is both the width and the depth (given the tubular cross arm is a square).
Width (Tube Type: 4F Rect)
Width is the dimension in the horizontal direction.
Depth (Tube Type: 4F Rect)
Depth is the dimension in the vertical direction.
Diameter (Tube Type: 6F, 8F, 12F and 16F)
This is the flat to flat diameter.
Wall Thickness
The wall thickness is the thickness of the material as shown below. The same definition applies to all Tube Types (Round, 4F Square, 4F Rect, 6F, 8F, 12F or 16F)
Flanged
Flanged crossarms are c-section beams. The parameters in the UI are shown below on the diagram.
Mass
The mass of the crossarm is used in loading calculations, depending on the options set in your Environments.
Material Strength
Maximum Bending Moment
The Maximum Bending Moment is only used in static analysis. It is used in the PDF reports (under the loading plots) that check if the cross arms pass or fail for the different environments.
If Finite Element Analysis (FEA) is used then the Max Bending Moment vs Horizontal/Vertical will be used instead.
Max Bending Moment vs Horizontal/Vertical
Second Moment of Area vs Horizontal/Vertical
Section Modulus vs Horizontal/Vertical
Torsion Constant
See Torsion Constant