Elastic boundary without tension capacity

SOFiSTiK Teddy
1

I’ve modelled a simple RC wall with elastic boundaries at top and bottom. Is it possible to make the elastic boundaries only active in compression? I’m trying to represent a precast RC wall on unreinforced mortar.

+PROG SOFIMSHA urs:3
HEAD #wall_ID
SYST TYPE GDIV GDIR
     3D   10E4 NEGZ
GRP  NO   1
NODE NO   X    Y    Z    
     101  0    0    0    
     102  #L   0    0   
     201  0    0    #H  
     202  #L   0    #H  

QUAD NO   N1   N2   N3   N4   MNO  MRF  T         KR   M         N
     MESH 101  102  202  201  11   12   #t[m]     POSZ #L/#dx   #H/#dx
ECHO OPT  SECT VAL  NO

BOUN 1    TITL 'BOUN_GRP';
     BOUN NA   101  NE   102  NM   FIT  TYPE CX   CA   1E3
     BOUN NA   101  NE   102  NM   FIT  TYPE CY   CA   1E3
     BOUN NA   101  NE   102  NM   FIT  TYPE CZ   CA   1E3
     BOUN NA   201  NE   202  NM   FIT  TYPE CY   CA   1E3
END
2

Hello

Non-linear effects, such as a spring failure load, can not be calculated with an elastic boundary element. You have to use multiple springs with non-linear stress-strain curves or a material with a tensile stress maximum.
Please have a look at the following commands. They will help you understand the workflow.

  • BMAT CRAC… (AQUA)
  • SPRI CRAC … (SOFiMSHA)
  • SPTS CRAC … (SOFiMSHC)

Keep in mind that non-linear effects are not considered within a linear analysis. You have to run a non-linear calculation with ase.

I would advise you to test the program behaviour with SOFiPLUS(-X) / the SSD and export the relevant tasks to .dat. I have created a short example for you that demonstrates a possible workflow.

Zugausfall Stabbettung.sofistik (37.0 KB)
Zugausfall Stabbettung.dwg (72.2 KB)

Best regards
Frederik Höller
Your SOFiSTiK Support Team

3

Hi Frederik

Thank you for the hints. Unfortunately, I cannot open your example (I’m operating with a 2018 version), but I have tried to model the supports as SPRI-elements as shown below (I’ll try to keep the modelling in SOFiMSHA). However, the springs keep having tensile forces - what am I missing?

+PROG SOFIMSHA
    HEAD #wall_ID
    SYST TYPE GDIV GDIR
         3D   10E4 NEGZ
    GRP  NO   1
    NODE NO   X    Y    Z    
         101  0    0    0    
         102  #L   0    0   
         201  0    0    #H  
         202  #L   0    #H   

    QUAD NO   N1   N2   N3   N4   MNO  MRF  T         KR   M         N
         MESH 101  102  202  201  11   12   #t[m]     POSZ #L/#dx   #H/#dx
    ECHO OPT  SECT VAL  NO

    SPRI NO FIT NA 101 NE 102 DX -1 DY  0 DZ  0 CP 1E3
    SPRI NO FIT NA 101 NE 102 DX  0 DY -1 DZ  0 CP 1E5
    SPRI NO FIT NA 101 NE 102 DX  0 DY  0 DZ -1 CP 1E3 CRAC 0
    SPRI NO FIT NA 201 NE 202 DX  0 DY -1 DZ  0 CP 1E5
END

+PROG ASE urs:7
    HEAD Structural analysis
    LC   ALL
    SYST NMAT YES
    NSTR
END