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Video 01 - FAQ Explanatory Video

Figure 01 - Two Equal Surfaces with a Line Hinge in the Center

Figure 02 - Diagram of the Basic Internal Force m-x

Figure 03 - Error Message after Calculation

Figure 04 - Deformations of the System Acc. to the Error Message Shown in Figure 03

Figure 05 - Incorrectly Defined Line Supports in the Bottom System

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FAQ 003316 EN

23 July 2019

Paul Kieloch Results RFEM Structural Analysis & Design Finite Element Analysis

I have entered a line hinge in the center of the surface and the bending moment is not equal to zero at the line hinge. What can be the cause?

Answer

If the line hinge has been defined correctly, the problem may consist in the incorrect support definition.

Figure 01 - Two Equal Surfaces with a Line Hinge in the Center .

Although the system (see Figure 01) would seem to have the same value, a moment results in the mid-span from the determination of internal forces in the surface.

Figure 02 - Diagram of the Basic Internal Force m-x

In the present case, the cause can already be derived from the error message after the load case has been calculated.

Figure 03 - Error Message after Calculation

This results in very large deformations in the bottom system, so that this already indicates an incorrect support of the surface.

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When checking the line supports, it becomes clear that the bottom system is twisting about the global axis Y due to the missing restraint. Ultimately, this leads to the non-meaningful diagram of internal forces in the basic internal force m-x.

Figure 05 - Incorrectly Defined Line Supports in the Bottom System

If the line support is adjusted, the result is the expected one.