Definition of loading in Static stress with nonlinear material models analysis

[cff22]

Dear all

At the moment, I am running Static Stress with Nonlinear Material Models and I want to apply Gravity and an Acceleration in other directions (lateral loading).

I intent to apply from the beginning of the event the total value of the standard gravity (9.815 m/s2 approximately) and increase linearly the lateral load (from 0 to 0.3g where g is the standard gravity). Thus, I need to define the gravity and the lateral loading in different load curves.

The load curve defined for the standard gravity should have a multiplier equal to 1 throughout the event and the load curve for the lateral loading (acceleration in a direction perpendicular to the gravity) should start with a 0 multiplier and this value should increase linearly to have a multiplier equal to 1 in the end of the event.

However, the programme didn't allow me to do this, because when I tried to define different load curves for different load cases it just included in the analysis one of the load curves and, thus one type of acceleration. Basically, the programme didn't allow me to apply different accelerations with different load curves for the analysis.

The programme allowed me to define a load case with the following inputs:

Acceleration due to body force: 9.81456
X multiplier: 0.3
Y multiplier: 0
Z multiplier: -1

However I just could assign a load curve for this loading which means that both standard gravity and the lateral acceleration are increasing linearly during the event (from 0 multiplier to 1 multiplier).

Attending to the situation described above, I would like to know whether is it possible to define different load curves for different gravity/acceleration load cases and if it is how that could be done.


Thank you.


Best regards,

[S.LI]

You are right. In current package, only one Gravity/Acceleration is allowed.

But there is an alternative way for your problem with a special load curve design.

According to your description here, the load need to be 1g at the beginning and 1.3g at the end.

Let's assume it starts at 0 second and ends at 1 second.

Your load curve could be

0                     0

0.001             1

1                     1.3

With this one, the constant gravity is applied from 0.001 second. Of course you can change it to any other number, which is much smaller than the whole load period.

[cff22]

Thank you for your idea.

The only problem is that I want to apply accelerations in two different directions. The acceleration that I want to apply from the beginning is parallel to Z because it is the weight of the structure and the other acceleration is parallel to the X-axis or to the Y-axis which is the lateral loading due to an earthquake. How will the programme know that the weight of the structure should be applied from the beginning and the acceleration in the other direction should linearly increase?

Regards

[S.LI]

Sorry, I didn't notice the direction problem. 😞

It seems no way to combine non-proportional loads in different directions linearly.

I have another way, but may not accurate.

Leave the normal gravity/acceleration load for the lateral one, and deal the constant gravity with "centrifugal load".

The acceleration for centrifugal load is \omega*\omega*r. Set \omega*\omega*r = 1g, and you can select a relative large r and smaller \omega, so that the effect of your model size is almost ignored on comparison on the huge r here.

Hope it's helpful.