FAQ 001448 EN-US

12/01/2017

Robert Vogl Calculation RFEM RSTAB

Can I also design a cable truss in RSTAB?

Answer

Yes, you can. Cables only absorb tensile forces. Thus, it is possible to calculate cable chains, taking into account longitudinal and transversal forces. For this, it is necessary to define the entire cable as a cable chain consisting of several cable members. You can quickly create chain lines using the menu "Tools → Generate Model → Arc." The more precisely corresponds the initial shape of the chain line to the real cable chain, the more stable and faster is the calculation.

It is recommended to prestress the cable members. In this way, you prevent compressive forces that would result in a failure. Also, cables should only be used if the initial deformations represents a significant part of the changes of the internal forces, that is, if large deformations may arise. In the case of a simple linear stay, for example a projecting roof, tension members are completely sufficient.

When evaluating the initial deformation mode, the display factor in the control panel is set to "1," so that the tightening effects appear realistic.

The large deformation analysis, also known as "cable theory," takes into account longitudinal and transversal forces in the analysis. In the analysis, the stiffness matrix is created after each iteration step for the deformed system.

Locally defined member loads are handled in such a way that the load direction is used as applied to the undeformed system. All internal forces are transformed to the member axis system. The members of the "cable member" type are always calculated according to the large deformation analysis. The rest of the members are treated according to the selected calculation method.

Keywords

cable cable theory cable chain large deformation analysis deformation prestress cable structure

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RFEM Main Program
RFEM 5.xx

Main Program

Structural engineering software for finite element analysis (FEA) of planar and spatial structural systems consisting of plates, walls, shells, members (beams), solids and contact elements

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RSTAB 8.xx

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The structural engineering software for design of frame, beam and truss structures, performing linear and nonlinear calculations of internal forces, deformations, and support reactions

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