Moving Load on Curved Surfaces

[MoRe19]

As part of my master's thesis, I need to model a person walking on a bridge.

For this, I have a model of the bridge in RFEM 5.

I have tried to model the moving load using the RF-BEWEG Surfaces add-on module. This works on a flat surface.

However, the bridge has a camber, so I need to model the moving load on a curved surface. I tried to assign a curved surface in the RF-BEWEG Surfaces module, but this does not work.

Can you help me if there is another trick to model the moving load on a curved surface?

[sandy.matula]

Hi MoRe19,

Thank you for your message!

The live loads should also work on curved surfaces. I have just successfully tested this myself.

To analyze the problem more precisely, the model file would be very helpful:

Click on File → Save As and choose the following settings to reduce the file size:

Then upload the file here (e.g., *.rf6, *.rs9) – this way the community can also contribute to the solution.

Don’t want to share the file publicly? No problem – send it to me via direct message: click on my profile picture or my username → Message.

Best regards
Sandy

[sandy.matula]

Please note the following points to ensure that moving loads can be applied correctly:
• Moving loads cannot be applied on spline surfaces or on surfaces with a thickness of zero.
• Instead, use quadrangular surfaces with the standard stiffness.

Also important:
• The lines must be integrated into the surface so that loads can be applied to them.

If you keep this in mind, applying the moving load should work without any problems.

[MoRe19]

Hello Sandy,
thank you for the help. However, the surface must not have any influence on the behavior of the model.
If I set the stiffness of the surface to standard, I have to assign a material to the surface, and then it does have an influence.
Is there a way to model the surface without it having any influence?

[sandy.matula]

If the surface should have no influence on the load-bearing behavior of the model, then the only option is indeed a modeling with negligible stiffness.

Possible procedure:

1. Surface type
   • Quadrangle/ Standard
2. Material
   • Create a custom "user-defined material"
3. E-modulus
   • Strongly reduce the modulus of elasticity so that the stiffness is almost negligible
4. Thickness
   • Define a very small thickness

In this way, the surface remains present and evaluable in the model without significantly affecting the global load-bearing behavior.

[MoRe19]

All right. I have defined the area based on the specifications. However, the Rf-Movement Areas module cannot generate load cases.

I cannot integrate the lines into the area because they are already the boundary lines.

[sandy.matula]

Hi MoRe19,

Thank you for your feedback!

To analyze the problem more precisely, the model file would be very helpful once again.

Best regards
Sandy Matula

[sandy.matula]

Thank you very much for the model file!

Please note that boundary lines do not need to be integrated into the surface.

Regarding RF-BEWEG:
• Due to the existing eccentricities, no load cases can be generated.
• The cause is probably the curved surface.

Here you would need to consider an alternative approach.

[MoRe19]

Ich habe versucht eine alternative Vorgehensweise ohne Exzentrität zu benutzen. Jetzt kommt jedoch ein anderer Fehler, wenn ich versuche die Liniensätze zu definieren

[sandy.matula]

Unfortunately, I don't have a concrete idea for an alternative approach, but this variant does not seem to work.

The message appears when no loads can be generated with the inputs made.

Please carefully check your inputs again.

[MoRe19]

Guten Tag,

ich habe eine Lösung gefunden und konnte das Modul Rf-Beweg Flächen benutzen.
Bei der Berechnung der Dynamischen Lastfälle mit RF-Dynam Pro treten allerdings Fehlermeldungen auf, wegen einer Singularität der Steifigkeitsmatrix. Hat das vielleicht etwas damit zu tun, wie ich die Fläche modelliert habe, um die Last aufzubringen?
Hier ist noch ein Screenshot, sowie das aktuelle Modell:

AGIB1950_Escherstrasse_koeln_rev10 Kopie.rf5 (1,8 MB)