Change material stiffness in TAPLA


I have a tunnel structure resting on clay material. The stiffness of the clay material changes as the tunnel is loaded and unloaded through varying construction stages.

In order to avoid having, literally, thousands of different clay materials, I want to change the stiffness of the soil groups using the CGRP feature allowing me change the “factor for stiffness of group” (Chapter 3.17 in the the TALPA manual).

I’m experiencing some issues with this process though and have a few questions I hope answered:

  1. In the table, the Item is called “FAKS”, but looking through the examples and the manual I find now other references to FAKS, as such I assume this is a mistake, and the actual item should be “FACS”?
    At least I’ve managed to apply the factor as:


CGRP NO 171+#i ACT MODI FACS #E_Factor(#i)
  1. The next issue I face is that I apparently can’t apply factors larger than 1.00, is that correct? If so, why?
    For now I’m using a workaround where I factor all stiffnesses based on the maximum value, as such, all factors are between 0 and 1, but It’s not terribly intuitive.

  2. Is the factor based the stiffness in the previous construction stages, or on the initial stiffness? Meaning, If I apply CGRP NO 1 ACT MODI FACS 0.5 in CS 1 and CGRP NO 1 ACT MODI FACS 0.2 in CS 2. Does this amount to a stiffness factor of 0.5*0.2 = 0.1 or does the factor in CS 2 overwrite CS 1 such that the stiffness factor = 0.2?

Not an expert TALPA, but here’s a few pointers that might help:

  • If there is a command you do not recognize (like FAKS vs FACS), it’s almost always a translation error. If you find the position (chapter and position of the subcommand) you might be able to figure it out.
    And yes, they mean FACS (German version FAKS)
  • In order to understand CSM a bit better you need to realise that it is basically a macro generator that produces several ASE inputs after each other. (Maybe an AQB here or there if you have a beam system)
  • If you open the your_project_csm.dat you can see the options CSM choses for your ASE calculations, i.e.:
    -Which groups are active
    -Which prev loadcase is used as a primary loadcase
    -Which “regular” loadcase is copied into your csm stage
    -Which control parameters have been chosen (creep, stiffness, etc)

Hope it helps.