Problem in modeling of loading-unloading behaviour of structure with non-linear modeling

SOFiSTiK Teddy
1

Hi,

I’m try to model the simple span of concrete structure just for educational purpose, with load on midspan, the loads looks as a series of loading-unloading like this (0,1,0,2,0,3,…)kN.

I’m considering nonlinearity, in material concrete and steel-reinforcement. I plan to capture the residual deformation during unloading (if any, and started from which magnitude of loading), and also the weakening of stiffness (EI_reduced) for every load step, In my understanding, I should assign every load in the series to the different load case, and assign Primary load case in the ASE module for every load cases, with the previous load, to capture the previous displacement, but is it works if we do unloading, or should we apply load the same magnitude to the negative direction to cancel the load? and I got an error when assigning PLC that my previous load case in the 2nd step is not detected or stored, even though the 1st load case runs successfully.

I want to upload my Teddy script but unfortunately I’m unable to do that for now, hence I leave it here, the complete script (fyi LC 1 is the loadcase where 1kN is imposed at the mid of the structure in linear analysis, all the other nonlinear load case created by multiplying LC 1 with the factor). Any help to solve this problem will be appreciated.

+prog aqua urs:1
head test - modifizierte Stahlarbeitslinie

echo full full

norm din en199x-200x
unit 0

conc 1 c 30  fct 0
stee 2 b 500
  ssla calc
  ssla eps sig type=pol
  -25.0000 -525.0000
   -2.5000 -500.0000
         0         0
    0.0495   50.0711
    0.2451   65.0925
    2.4197  500.0000
   14.5678  525.0000

sect 1 mno 1 mrf 2
  poly o mno 1
    vert y z
      0.06 -0.1
      0.06  0.1
     -0.06  0.1
     -0.06 -0.1

  rf y 0 z 0.1-0.032 as 3.14

end

+prog sofimsha urs:2
head test - modifizierte Stahlarbeitslinie

syst 3d gdiv 100

node 1 0 0 0 fix ppmx
node 21 2 0 0 fix pypzmx
node imsh 1 21 1

grp 1
  beam no mesh na 1 ne 21 ncs 1 div 20

end

+prog sofiload urs:3
head test - modifizierte Stahlarbeitslinie

lc 1
  node 11 pzz 1

end

+prog ase urs:4
head test - modifizierte Stahlarbeitslinie
head linear elastisch

lc 1

end

+prog ase urs:5
head test - modifizierte Stahlarbeitslinie
head nichtlinear

LET#X 100
LET#A(0) 0
loop#i #X
    if mod(#i,2) == 0
        LET#A(#i) 0
    else
        LET#A(#i) ((#i+1)/2)+1
    endif
endloop

$ load first step in nonlin analysis
syst prob nonl
nstr kmod S1 ksv cal ksb cal

lc 11
    lcc 1 fact 1

$ Loop to create analysis for the rest of the load
loop#i #X
  syst prob nonl plc 11+#i

  lc 12+#i
    lcc 1 fact #A(#i)
  end
endloop

end
2

Hi,

nonlinear loadcases in ASE have to be separated by an END:

+prog ase urs:5
head test - modifizierte Stahlarbeitslinie
head nichtlinear

LET#X 100
LET#A(0) 0
loop#i #X
if mod(#i,2) == 0
LET#A(#i) 0
else
LET#A(#i) ((#i+1)/2)+1
endif
endloop

$ load first step in nonlin analysis
syst prob nonl
nstr kmod S1 ksv cal ksb cal

lc 11
lcc 1 fact 1

end
$ Loop to create analysis for the rest of the load
loop#i #X
syst prob nonl plc 11+#i

lc 12+#i
lcc 1 fact #A(#i)
end
endloop

end

But this will give you the next error message:

+++++ error no. 650 in program BEAM_DEHN_PLF_CHECK
Nonlinear beams with PLC primary loadcase only allowed with NSTR KN.

Best regards,

Nora

3

Hi, many thanks for your reply,

Yeah I encounter this error when I change the used approx. non linear stiffnesss to KN. When I use KN, the calculation somehow diverges :’\

are there any ways, that engineer commonly used to taking into account the damage of previous loading in subsequent analysis, especially I want to capture the deformation when I’m doing the unloading (to see residual deformation), what is the module or function that is available for this cases?

Regards,