The RM Bridge Analyzer: Properties: Cross Sections: FE Mesh Move and Rotate the Nodes is a button with an option to modify current cross-section properties to achieve specific purposes. It is important to note that this function is principally related to all nodes of the current cross-section. The total mesh is translated in the cross-section coordinate system by a certain amount or rotated around the center of gravity or at another reference point. Usually, superelevated or unsymmetric cross-sections might be the ones that require user intervention to get cross-section-related calculations right.

As shown in the figures below, for this example, a BCB - Balance Cantilever Bridge - has a variable Superelevation and this causes the local z-axis and local y-axis of the cross-section to be originally rotated in the real structure. By using the Move and rotate the nodes button user can reinstate the local axes references to the global position for the purpose of stress distribution and calculations. This is performed by Selecting the options Update element beta and Initialize, and the result would be a leveled CS aligned to the principal elements axis. 

     

There are three possible sets:

• Move: The nodes of a cross-section are moved in the cross-section coordinate system by a certain amount.  
• Rotate: The FE mesh is rotated in the cross-section coordinate system. The rotation is performed around the point with the coordinates Z-off and Y-off. A rotation around the reference point of the cross-section is in general required; this reference point is the point where the node of the structural model is arranged if no additional eccentricity vector is defined. The coordinates of this point are therefore specified as default when the switch for rotation is selected.
• Modify Element Beta: 
  • Initialize: The element beta angle value will be initialized by the CS beta angle value
  • Update: The current CS beta angle value will be added to the element beta angle previously defined in the elements table.