# Member Type

### Glossary Term

A member type controls member stiffnesses and properties applied in the structural analysis.

The most commonly used member type is a beam: This rigid member can transfer all internal forces.

###### Member Types
• Beam
A beam is a rigid member which is able to transfer all internal forces. When two beams are connected with each other and no hinge has been defined for the common node, the connection is bending-resistant.
• Rigid member
A rigid member couples displacements of two nodes by means of a rigid connection. Basically, it corresponds to a coupling member, but customized hinges can be assigned at the member ends.
The following stiffnesses are applied during the calculation:
• Longitudinal and torsional stiffness: E ⋅ A = G ⋅ IT = 10 13 ⋅ l
• Bending stiffness: E ⋅ I = 1013 ⋅ l 3
• Shear stiffness: GAy = GAz = 10 16 ⋅ l 3 with l = member length
• Rib
A rib allows you to define a downstand or upstand beam with effective slab widths. Within the effective slab widths, the slab internal forces are integrated and added to the member internal forces.
• Truss
A truss is a beam with hinges located at the member ends which do not transfer any moments.
• Truss (only N)
A truss (only N) has only one longitudinal stiffness E ⋅ A. Moment hinges are arranged at the member ends.
• Tension / Compression
A tension member is a truss (only N) with the additional property to only absorb tensile forces. A compression member only transfers compressive forces.
• Buckling member
A buckling member is a truss member (only N) with the additional property of failure under a compressive force that exceeds the buckling force Ncr .
• Cable
Cables only absorb tensile forces. They are used to analyze cable chains with longitudinal and transversal forces by iterative calculations taking into account the cable theory (large deformation analysis).
• Cable on Pulleys
The cable on sheaves can only absorb tensile forces and has only one possible displacement of the inner nodes in the longitudinal direction ux . This member type is calculated according to the cable theory (large deformation analysis) and is appropriate for calculating pulley systems where axial forces are passed on by means of deviating points.
• Result Beam
A result beam has no stiffness and has no influence on the structural analysis. The result beam is a tool to integrate surface, solid or member results in a predefined area for the subsequent design.
• Definable Stiffness
With this stiffness member type, it is possible to assign user-defined stiffnesses to a member for the structural analysis.
• Coupling
A coupling member has the stiffness of a rigid member. In addition, when using the coupling member, the degrees of freedom of the start and end nodes are defined depending on the settings. The following coupling members are available:
• Coupling Rigid-Rigid: a bending-resistant connection at both ends of the coupling member
• Coupling Rigid-Hinge: a bending-resistant connection at the member start and a hinged connection at the member end
• Coupling Hinge-Hinge: a hinged connection at both ends of the coupling member
• Coupling Hinge-Rigid: a hinged connection at the member start and a bending-resistant connection at the member end
• Spring
A spring allows you to define spring stiffness for a member.
• Null member
A dummy member is not considered in the calculation. Dummy members are used, for example, to analyze the structural behaviour of a structure where certain members are not effective.

#### Reference

 [1] Manual RFEM. (2018). Tiefenbach: Dlubal Software. [2] Manual RSTAB. (2013). Tiefenbach: Dlubal Software.

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• Updated 19 April 2021

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