Benchmark solution
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The law of behavior DASHPOTlie, at each calculation moment :math:`{t}_{i}`, the nodal force :math:`F({t}_{i})` at the displacement increment :math:`{\mathrm{\Delta }}_{x}({t}_{i})` in the following way: :math:`F({t}_{i})=K{\mathrm{\Delta }}_{x}({t}_{i})` where :math:`K` is a stiffness parameter provided by the user.

In this test, the following on-the-go loading is required: :math:`U(t)=\mathrm{sin}(\mathrm{\omega }t)`.

The analytical solution for force is therefore expressed as follows: :math:`F(t)=K\mathrm{\omega }{\mathrm{\Delta }}_{t}\mathrm{cos}(t)` where :math:`{\mathrm{\Delta }}_{t}` is the time increment.