Shutting Off the Containment Unit

If you've used OpenSees--even if you're a geotech--you've used the force-based element. When Remo implemented the force-based element, it was the only material nonlinear frame element available in OpenSees (G3 at the time); thus, the original name nonlinearBeamColumn. Only after a standard displacement-based frame element (dispBeamColumn) was added did we change the name from nonlinearBeamColumn … Continue reading Shutting Off the Containment Unit →

Not All at Once

I've been working on a project where we use OpenSees to analyze structural models for several load cases. We only care if the models can support the full load, not so much how they get to the full load. We apply all the load in one step with load control and Newton-Raphson. If that succeeds, … Continue reading Not All at Once →

Failed to Get Compatible …

If you've used the force-based beam-column element in OpenSees, you've likely come across this warning involving element forces and deformations: I've encountered this warning many times and so have others. In fact, I lifted the above image from a recent post on the OpenSees Facebook group. I tried to come up with a MWE to … Continue reading Failed to Get Compatible … →

Better than Ideal Conditions

In simulating the nonlinear response of structural models, the Newton-Raphson algorithm converges quadratically as the iterations approach equilibrium at a time step. Quadratic convergence means the error at the current iteration is less than some constant times the square of the error at the previous iteration, e.g., the error is on the order of $latex … Continue reading Better than Ideal Conditions →