Question:
How can I model double members in RSTAB 9, such as those in a telescopic connection?
Answer:
The interlocking components of a telescopic boom of a construction machine, for example, transport their forces mechanically between the components.
This special force transfer can be solved in RSTAB 9 as follows:
A characteristic plug connection like the one shown in the sketch consists of four members. Two members (members 2 and 4) lie on top of each other in the overlap area.
You can create superimposed members using nodal releases. For this, you have to define a nodal release at node 2 which releases member 1 and member 2. The nodal release creates node 5, which acts as the end node of member 1 and the start node of member 2. Member 1 and member 2 are rigidly connected to each other.
Now, you can define the overlapping member 4 between node 2 and node 3. It is also necessary to define a nodal release at node 3, which releases member 3 and member 4. The nodal release creates node 6, which acts as the end node of member 4 and the start node of member 3. Member 3 and member 4 are rigidly connected to each other.
To ensure that the force is only transported via a force pair at the ends of the overlapping members in accordance with the design, constraint conditions between nodes 2 and 5 as well as nodes 3 and 6 must be defined as the nodal release type in the nodal releases.
A moment hinge in the nodal releases between nodes 2 and 5 and between nodes 3 and 6 is intended to ensure that the bending moment loading between the red continuous members (members 1 and 2) and the green continuous members (members 3 and 4) is transferred via a pair of forces at the ends of the overlapping members.
An axial force hinge in the nodal release between nodes 3 and 6 is intended to ensure that an axial force loading is only transferred between the green and red continuous members at the planned fixation.