Using Result Beam in RFEM

Technical Article

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Since the release of RFEM 5, the “Result Beam” member type has been available. The result beam is a virtual member that does not have any stiffness nor require any support. It can be used in various situations in order to integrate the results from members, surfaces, and solids, and to display them as member internal forces.

Input

After selecting the "Result Beam" member type, you have to specify additional parameters. There are four options for specifying the integration area:

  • Within the box - Square: A quadratic integration area is used whose center of gravity lies in the member axis.
  • Within the box - General: A rectangular integration area is used whose center of gravity can vary.
  • Inside the cylinder: A circular integration area is used whose center of gravity lies in the member axis.
  • Of defined inclusive objects: Only the elements that are listed in the "Including Objects" list below and that are within the possible effective range (see next section) are used for the evaluation.

If the integration area overlaps objects that are not to be considered, select them in the "Excluding inclusive objects" list.

Scope of the result beam

A result beam can only provide results of elements located within a perpendicular axis of the member start and the member end. All elements outside these limits are not taken into account.

For clarification: The areas marked in red on the right are not used for the results. The turquoise surfaces were modeled manually as auxiliary surfaces and represent the limits of the result member.

Figure 01 - 1 - Effective Area

Cross-section

For the internal forces of the member, it is irrelevant which cross-section is used. If you want to use the result beam only for the determination of internal forces, you can use any cross-section. However, if you want to perform a subsequent design in the add-on modules such as RF-STEEL EC3 or RF-CONCRETE Members, the cross-section plays an important role and should then be defined precisely.

Member Division of Results

To ensure that the internal force distribution does not show a too rough distribution, the number of member divisions for result diagrams should be set higher in the global calculation parameters.

Figure 02 - 2 - Division of Members

Position of result beam

For the internal forces N, V y and V z , the parallel distance of the result member to the centroid of the integrated objects is irrelevant. If you only want to evaluate the axial and shear forces, you can model the result beam next to or above the structure for a clear display.

For the internal forces M t , M y, and M z , however, it is crucial that the result beam is placed in the center of gravity of the considered objects. In addition to the integrated moments, the axial forces multiplied by the distance of the individual FE mesh points are added to the center of gravity of the result member.

Figure 03 - 3 - Position of Result Beam

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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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