Non linear analysis

ligy · Jan 28, 2015

Hi!

I'm just trying to perform a non linear analysis with Gt Strudl, namely taking into account geometric non linearities.
Previously I did a response spectrum analysis and I transformed the results in a Pseudo static loads. After I combine these Pseudo static loads with other static loads by means of the command FORM LOAD. When I tried to perform the non linear analysis, the results miss the seismic part (the contribution to the final internal actions coming from the seismic loads is zero). It's like either the FORM LOAD command can't consider Pseudo static loads or the non linear analysis can't work with Pseudo Static Loads.
I'll write here a piece of the program:

PERFORM RESPONSE SPECTRUM ANALYSIS

COMPUTE RESPONSE SPECTRUM DISPLACEMENTS ACCELERATIONS FORCES REACTIONS MODE COMBINATION CQC
CREATE PSEUDO STATIC LOAD 'Ed_X' FROM CQC OF LOAD 'LEd_X'
CREATE PSEUDO STATIC LOAD 'Ed_Y' FROM CQC OF LOAD 'LEd_Y'
CREATE PSEUDO STATIC LOAD 'Ed_Z' FROM CQC OF LOAD 'LEd_Z'

FORM LOAD 'C1' FROM 'G' 1.0 'Q' 0.5 'Ed_X' 1.0 'Ed_Y' 0.3 'Ed_Z' 0.3
FORM LOAD 'C2' FROM 'G' 1.0 'Q' 0.5 'Ed_X' 1.0 'Ed_Y' 0.3 'Ed_Z' -0.3
FORM LOAD 'C3' FROM 'G' 1.0 'Q' 0.5 'Ed_X' 1.0 'Ed_Y' -0.3 'Ed_Z' 0.3

NONLINEAR EFFECTS
GEOMETRY ALL MEMBERS

MAXIMUM NUMBER OF ITERATIONS 10
NONLINEAR ANALYSIS

Here you are.. Please help me! Thankyou!

transmissiontowers · Jan 28, 2015

I do Non-Linear analysis but for static loads and not any spectrum analysis but after you create the loads and make the Form loads, I usually have to issue a Load List command to tell the program what load cases to consider during the analysis. I don't think just because you used the Create command and the Form Load command, the program still has to be told which loads to use for the NLA. Since the Form Load command is doing the loads you want, you might use:
Load List 'C1' 'C2' 'C3'
then you do the NLA command. You can also use Load List All, but that will cause some extra analysis time.

If that does not solve your problem, and you have paid for support, you can contact Intergraph Tech Support and get one of the real experts to find your problem.

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