In RM Bridge the definition of Cross Sections (CS) is completely independent of Alignments, Axes and Segments. Therefore it can be previously defined as cross sections will be later assigned to the respective Elements in the Segments definition to create the elements in the Main Girders, Piers, Cross Members or Cables menu. This set can be easily changed just by modifying the reference names, as shown in the program screenshot below. Each element subdivision creates segment points and in each of this points there can be a variable or a cross-section modification with the options before and after.
For modeling the cross sections a totally separate coordinate system is used based at the Construction Lines (CL). Their intersections are used to compose the Finite-Elements cross-section. It is important to understand that all CL are dependent from a Reference of one previous existing Base line creating a relationship that is used to create the parametrization thru variables and respective tables or formulas. Additionally the generated Parts are used to differ Composites, Elements beams and their respective Nodes, as shown in the picture below. Several Parts can be created in the same cross-section for creating either a Composite Element or separated elements with or without the same nodes. The elements Nodes are generated where the Part is applied while the element axis is considered in the original point of application: the intersection of CL1 (the Local Z-axis) and CL2 (the Local Y-axis), as shown in the RM User Manual picture below. If necessary for accuracy or to calculate correct stresses in unsymmetrical CS, it is possible to translate and rotate the CS to adapt the local axes of the beams to the directions of the principal inertia axes of the cross-sections.
More information can be found in the application Menu Help F1 and at the RM Bridge Modeler and Analyzer User Manuals.