For elements type Cable there are also different considerations for the cable behaviors: linear, CabSag, or Stay Cable Nonlinear. Depending on the type of analysis performed, each one could be more advantageous:
RM Bridge CONNECT Edition offers different forms of cable force load definitions for stressing the cables: FCAB, FX0, and LX0.
The big difference is the consideration of cable sagging for FX0 or LX0. This is required for longer cable elements and, as the cable is external to the structure, the cable sag is a complex calculation that is different from prestressing. For medium structures, the cable curvature due to gravity has to be taken into account and this is relative to the level of tension.
There is a long iterative process to calculate the full bridge that includes not only the calculation of the final structure but also the construction stage calculation. So, one of the most important non-linearities in this type of analysis is the continuous change of the structural system caused by the evolution of the construction schedule. There are two options: Accumulate Loads or Accumulate Stiffness (more usual); and, if the analysis and design include construction control, there is the additional option Erection Control with or without construction kink.
AddCon: Additional Constraints technique can be used to perform structure optimization allowing the user to specify boundary conditions to be achieved and follow the variable forces factors convergence process to achieve a solution.
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