The load application point is decisive when applying forces to members, as additional moments can result from the distances to the center of gravity or the shear center. The load application point is particularly important for a geometrically non-linear calculation, since an eccentric load can increase or decrease a rotation (see also the parent chapter # extbookmark manual|load-behavior-GNA|Load #).
In the following, you will find information on the load application point for the load types relevant for a calculation with 7 degrees of freedom.
Member and set loads
If you define a member load without eccentricity, the load always acts in the center of gravity in the calculation with 7 degrees of freedom. By activating the 'Eccentricity' option in the edit dialog box for a member load, you can specify the load application point yourself. The center of gravity, the shear center and specific edge points of the cross-section are available. It is also possible to enter eccentricity values with reference to the selected point.
The 9 points relate to the center of gravity and the local member axes. The middle point corresponds to the center of gravity, the 8 edge points stand for the intersection points of the local member axes with the edge lines of a rectangle circumscribing the cross-section. This provides you with a simple definition option for typical situations (such as the 'left corner of the top chord' on an I-section).
Nodal Loads
Nodal loads always refer to the position of the definition node. After activating the 'Eccentricity' option in the editing dialog box, you can specify an eccentricity value for each direction of the selected reference system. You can specify the eccentricity values manually or by using formulas and calculate them from existing cross-section values.
Load distribution areas
In RFEM, you can use load distribution surfaces to distribute a load acting on the surface to integrated members. It should be noted that the load from a load distribution surface is always assumed to act in the center of gravity. This also applies to members arranged eccentrically to the load application surface, if they have not been excluded from the load distribution beforehand. It is currently not possible to take a connection eccentricity into account.
Further information can be found in chapter # load transfer surfaces of the RFEM manual.
Load Wizards
Various load wizards are available in RFEM and RSTAB for generating wind or snow loads. Please note that the load generated by the load wizard is always assumed to act in the center of gravity. This also applies to members arranged eccentrically to the load application surface, if they have not been excluded from the load distribution beforehand. It is currently not possible to take a connection eccentricity into account.
Use the 'Split Generated Loads' function to convert the generated loads into member loads and to use the eccentricity settings described in section member-loads . Further information on the load wizards can be found in the RFEM manual in chapter Load wizards .
Load from adjacent components
If other objects are connected to a member to be calculated with 7 degrees of freedom, the connection point is always assumed to be in the center of gravity. Shear loads from an adjoining component or bearing thus generate an additional torsional moment depending on the position of the shear center.
If the connection is to be made at a different point, you can model the connection with rigid members or use member eccentricities. Further information can be found in the chapter # extbookmark manual|connection-adjoining-elements|Bars # of this manual.