# How are cable structures analyzed according to the large deformation analysis in RSTAB?

If you design a structure with beams, columns, and cable, RSTAB takes into account the large deformation analysis (cable theory) for the cables only. Cables can only absorb tension; they fail in the case of the negative axial forces.

The member type of "Cable" has the effect that the calculation is carried out according to the large deformation analysis so that cable chains do not result in a failure as it would be the case for the "tension member on tension member" arrangement. This is the major difference to the member type of "Tension." Thus, cables are automatically calculated according to the large deformation analysis considering longitudinal and transverse forces.

Tension members and cables have a stiffness in the longitudinal direction and in addition, cables have also an ideal stiffness in the transverse direction. This is 1/200 of the stiffness in the longitudinal direction. This stiffness s necessary to calculate a cable chain.

To correctly determine the cable sag line of deformed cables, it is necessary to model several connecting cable members (a cable chain). If this division is missing, the cable sag line will not be determined. Thus, the results are not plausible.