# Problem in contact force - Explicit Dynamics

Member

Hi,

I'm modeling an experiment experience in Explicit Dynamics. I modeled a concrete bridge deck with elastomeric bearings. The impact between the abutment and deck was modeled with body interaction. When a see the graphs of Contact force, i see positive force and i don't understand why.

Then a put 8 springs to try to measure de contact force, but a i have problems:

- Could not transfer loads and constrains to the solver

- Cannot apply multiple constraints to rigid part

- Failed to submit solve job. See Solution Information, which may contain more details.

- One or more parts were found to be unmodified so smart update.

The real problem is that a can't measure de impact force (Contact force) properly.

Regards

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## Comments

• Member

My reply in the discussion linked below may be illuminating.

https://forum.ansys.com/discussion/comment/99466#Comment_99466

• Member

Thank you.

Anyway why i have the errors that i mentionated before when i used springs?. My idea is that this springs represent all the load cells of the experiments.

Regards

• Member
edited December 2020
• Member

@peteroznewman i think that you wrote and answer, but it was erased.

Regards

• Member

Do you have a rigid part in your model? Is it the block with the 4 springs?

This error message "Cannot apply multiple constraints to rigid part"

That could be referring to the 4 springs. You can't have 4 springs on a rigid part.

Either don't use a rigid part or use just one spring per rigid part.

• Member

No, all the blocks are modeled with a nonlinear concrete material and yes i have 4 springs in a single block. In my model the external blocks, the base of the elastomeric bearings (bearings in red in the figure) and the inital point of the springs have displacements that represent an earthquake, so the springs quantify the force due the impact between the central and external block.

• Member

The end blocks represent the ground, which is moving according to the ground accelerations measured during an earthquake.

The earthquake measured ground accelerations can be integrated to ground velocity or ground displacement.

You want to simulate the impact between the end blocks moving with the displacement (or velocity) of an earthquake and the concrete deck, a large mass isolated from the ground motion by the elastomeric bearings.

I recommend you remove the springs and apply a transient velocity profile to the end blocks. They will collide with the bridge deck.

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