Adding internal forces to beam elements

SOFiSTiK Teddy
1

“I am working on a FE model for a pile-supported bridge pier. The piles are modeled with beam elements in Teddy I have received moment curves for the piles from a geotechnical model. I would like to include the moments from the geotechnical model as internal forces for the piles in my Sofistik model. How can I do this?”

If a load in “sofiload” is introduced as an external bending moment, the section forces in the piles will depend on the boundary conditions. Thats why I want to introduce the bending moment from the geo model as an internal section forces.

2

Hello,

When I do pile design, I ask the geotechnical engineer to give me the ground parameters they have used for the calculation of the internal forces. So I can replicate their calculations and results. It should give the same internal forces and displacements in a geotechnical model as in a embedded beam in Sofistik.

For your particular issue, I guess you want to design the pile, so maybe you are looking for something like CAPAin AQB?

3

Hi,

It seems like a good approach in general, but in this case the the geo model handles complex soil behaviour, as the soil itself introduce transverse pile forces. Thats why i want to introduce additional bending moments.

Do anyone know how this can be done?

4

Hello,

I think that if you want to design the pile, you can use the record “S” in the AQB module.

You need to create new load cases LC in which you inject the internal forces using the S record. Then, you use the COMB record to combine these additional forces with those from your model, which are logically the result of combinations generated by the MAXIMA module.

Best regards,
Abderrahman OMRI

5

It not my intention to use AQB for the design of the piles.

Would it be possible to create a load case with internal pile section forces that I can combine with other load cases in ASE?

6

No, it is not possible to directly define a load case that would contain internal forces (such as axial force, bending moments, shear forces) in the SOFiLOAD programme.

Here is why and how the roles of SOFiLOAD and AQB differ in this respect:

  1. Role of SOFiLOAD: SOFiLOAD is designed to generate external loads applied to the structure. These loads can be:

◦Nodal loads (NODE).

◦Loads on elements (BEAM, BEPL for beams, QUAD for surface elements, BRIC for volume elements).

◦‘Meshless’ loads (independent of the mesh) such as point loads (POIN), linear loads (LINE), surface loads (AREA) or volume loads (VOLU).

◦Dynamic loads, load trains (trains), or wind loads. These external loads are then used in structural analysis programmes (such as ASE or STAR2) to calculate the internal forces in the structural elements.

2.Definition of internal forces in AQB: The ability to directly define internal forces applied to a section, such as that of a pile, is a specific feature of the AQB programme. In AQB, you use the LC record to select a load case, then immediately after, the S record to define the internal forces and moments (N, VY, VZ, MT, MY, MZ, MB).

◦These internal forces and moments are then recorded under the load case specified by LC.

◦This is particularly useful for the analysis and design of individual sections, even if these forces do not come from a complete static analysis of the existing system.

◦It is important to note that this action deletes any pre-existing load results stored under the same load case number in the database.

In summary, SOFiLOAD is used to apply external loads that will produce internal forces after a structural analysis, while AQB allows you to work directly with internal forces on sections for their design and verification. These two programmes have complementary but distinct roles in defining what constitutes a ‘load case’ at their level.

Abderrahman OMRI

7

OK. Thank you for the explanation.

Would it be possible to setup a model using the following method:

  1. Define external loads in Sofiload
  2. Run load combinations with external loads in ASE. LC number 1001, 1002 etc.
  3. Define variation of internal forces along the length of beam elements in AQB
  4. Add internal forces from AQB to internal forces calculated in ASE for LC 1001, 1002 etc. Can this be carried out in ASE?

Could you setup a small example of the code in Teddy?

8

Hello,

Just to clarify: AQB comes after ASE, not the other way around. AQB is the design module, which is used only after all the calculation combinations have been finalized.

The typical workflow in SOFiSTiK is:
AQUA ⇒ SOFIMSH(A/C) ⇒ SOFILOAD ⇒ ASE ⇒ MAXIMA ⇒ AQB
Going in the reverse order simply won’t work.

So, if you want to design the pile and introduce additional internal forces, you should:

  1. Create new load cases using the S record to inject the internal forces.
  2. Use the COMB record to combine these internal forces with those resulting from the MAXIMA combinations.

Only then can AQB use these complete combinations for the design.

Best regards,
Abderrahman OMRI

9

OK. Thank you for the clarification.

Would it be possible for you to make a small example in Teddy where section forces for a beam element is calculated in ASE, and additional section forces are added afterwards in AQB? I will not use MAXIMA. I want to be able to view the combined section forces in Wingraf and extract the combined section forces in Excel.