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What is the difference between the basic internal forces, the principal internal forces and the design internal forces in RFEM?


basic internal forces

These are the surface internal forces that are related to the local coordinate system (x, y, z) of the surface. The x- and y-axes lie in the surface, the z-axis is perpendicular to the surface. The bending moment mx, for example, represents the bending moment that generates bending stresses in the x-direction (not about the x-axis!).

Principal Internal Forces

These are the internal forces related to the principal axes (1,2,3) of the surface. The internal forces in the direction of axis 1 represent the maximum values. The angle between the surface axis x and axis 1 is displayed as αb for bending moments.

design internal forces

These internal forces are required for the reinforced concrete design. + And - indicate the positive or negative side of the surface.

The surface internal forces are described in detail in the RFEM manual .


Basic internal force principal internal force Rated internal force


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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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