Modeling Plug-in Connection

Tips & Tricks

If you want to calculate the global load bearing capacity of a telescoping boom, for example of a construction machine with members, a special modeling technique with regard to structural connections as shown in the sketch may be useful because of its telescope mechanics.

A characteristic plug‑in connection like the one shown in the sketch consists of 4 members between 4 nodes. In the overlapping area, two members are overlapping, each connected to the same nodes 2 and 3. To avoid that force is transferred from member 1 across both members (2, 3) to member 4 simultaneously, you have to apply specific member end releases to the overlapping members. In this way, force is transported true to the construction by a force pair on the ends of the overlapping members. A moment release defined on member 3 at node 2 and on member 2 at node 3 is responsible for transferring the bending moment load of the red (1, 2) and green (3, 4) continuous members by a force pair on nodes 2 and 3. Furthermore, an axial force release defined on member 2 at node 3 makes sure that an axial force load will be transferred from the green to the red set of members only at the planned fixation on node 2.

Generally, RFEM and RSTAB identify overlapping members as modeling errors. They try to correct this arrangement automatically. Therefore, when you use the described way of modeling, you need to set the mode ‘Allow Double Members’ before you create the model.


Telescope plug connection member in member double member insert pushed in telescopic member


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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

Price of First License
3,540.00 USD
RSTAB Main Program
RSTAB 8.xx

Main Program

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

Price of First License
2,550.00 USD