3.3 Special Terms in RFEM

This chapter explains some important terms specific to RFEM. They are described in detail in the following chapters.

Table 3.2 RFEM-specific terms
Term	Explanation
Nodes	In the 3D model, a node is defined by its coordinates (X/Y/Z). Nodes are used to model the geometry of a structure.
Line	Nodes are connected by lines. In addition to straight connections, high-grade lines such as arcs or splines are possible.
Member	A member represents the property of a line. Through material and cross-section properties, a certain stiffness is assigned to the member. A member is a 1D element.
Set of members	Members can be combined into a set of members. In a continuous member, members are continuously connected to the node like in a continuous beam. A group of members consisting of connected members can join more than two members on a single node.
Surface	A surface is limited by lines. Through material and thickness properties, a certain stiffness is assigned to the surface. A surface is a 2D element.
Solid	A solid is surrounded by boundary surfaces (usually type Null). The stiffness is defined by its material properties. A solid is split into 3D elements for the calculation.
Nodal support	The degrees of freedom are limited for the node.
Line support	The degrees of freedom of all FE nodes on a line are limited.
Surface support	The degrees of freedom of all FE nodes in a surface are limited.
Nodal load	Force or moment applied to a node.
Line load	A line is loaded by a uniform or variable distributed load or by a concentrated load. The load acts as a force or moment.
Member load	A member is loaded by a distributed or concentrated load. The load diagram can be either uniform, linearly variable, or parabolic. In addition to forces and moments, temperature actions and prestresses are possible.
Surface load	A surface is loaded by a uniform or linearly variable load. In addition to forces, temperature loads and imposed deformations can act on the surface.
Solid load	A solid is loaded by effects of temperature or imposed deformations.
Load case LC	The loads from an action are managed in a load case, for example "self-weight" or "wind". The loads should be defined as characteristic loads (i.e. without factors). Partial safety factors can be considered in load or result combinations. A load case is usually calculated according to the linear static analysis.
Load combination CO	A load combination is used to superimpose load cases, that means all loads of the load cases in question are summarized. A load combination is usually calculated according to the second-order or large deformation analysis.
Result combination RC	A result combination sums up the results of the contained load cases. It is also possible to determine the extreme internal forces and deformations from different load cases, load combinations, or result combinations using an Or combination. However, the additive principle of superposition does not apply for results calculated according to the second-order analysis.

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