Tips for Squandering OpenSees

I recently came across a blog post by Prof. Amy J. Ko on how tenured faculty can accelerate the demise of tenure. Applying the same sardonic tone, here are five ways you can ensure OpenSees will also be gone sooner rather than later. 1. Don't learn - A firm grasp of linear analysis is sufficient … Continue reading Tips for Squandering OpenSees →

Earthquake Songs

You can find several lists of earthquake songs--mostly about shaking one thing or another, almost all non-structural. For example, here's a list of songs compiled in 2011. The list has the standard fare like AC/DC and Carole King, along with 90s nostalgia like Wreckx-N-Effect. If the list were updated today, Tyler the Creator's Earfquake from … Continue reading Earthquake Songs →

Cable Analysis

Analyzing cables subject to transverse loads is straightforward in OpenSees. Use a mesh of corotational truss elements with elastic uniaxial material. Of course, you can use any uniaxial material you like. The only trick is you have to scramble the nodes up a little bit--if you try to analyze a perfectly straight cable, you'll get … Continue reading Cable Analysis →

Make a Pull Request

If a tree falls in a forest and no one is around to hear it, does the tree make a sound? If a model is coded in OpenSees and no one pushes it upstream on GitHub, does the model exist? Is there only the perception that the tree makes a sound and that the model … Continue reading Make a Pull Request →

Initial Conditions

There are a couple ways to set initial conditions for nodal displacements and velocities in OpenSees. If you look at the end of this post, you'll see the hard way to do it: set initial displacements as single point (sp) constraints in a load pattern, do one analysis step, then remove the load pattern prior … Continue reading Initial Conditions →

Monte Carlo Simulation

The uncertainty associated with a finite element analysis is as important, if not more important, than the results of the analysis itself. Thanks to Terje Haukaas, OpenSees has several modules for finite element reliability analysis: FORM, FOSM, SORM, and several other methods to quantify uncertainty. Unfortunately, those methods have not yet made their way into … Continue reading Monte Carlo Simulation →

Means and Ends

OpenSees is often a means to an end, or an instrument, with the end being an advanced degree. There is nothing wrong with that! But OpenSees can also be an end in itself. You can learn to automate workflows, to think algorithmically, and to manage data structures--all in the context of earthquake engineering. That end … Continue reading Means and Ends →

Five Tweets from the Bot

The OpenSees Twitter bot is almost two years old. The bot has 356 followers, compared to 200 followers a year ago. Impressive OpenSees work continues to be tweeted. Here are five of the most recent tweets gleaned by @OpenSeesTweets. https://twitter.com/NHE_SimCenter/status/1460763867047501831 https://twitter.com/ccaprani/status/1459045946159812608 https://twitter.com/mikusscott/status/1451608792135651330 https://twitter.com/SilviaMazzoni_/status/1450195727783641088 https://twitter.com/6icees2021/status/1447127835261480960

Repeated Section Modes

If you use a section with linear-elastic response in the displacement-based, force-based, and mixed beam-column elements in OpenSees, you will get the same response from all three elements. True False It depends The answer is it depends on the type of "section with elastic response" you use. Also, I wouldn't include "It depends" as a … Continue reading Repeated Section Modes →

Trying to Get a Reaction

OpenSees does not compute reactions automatically because this can be a time consuming process--OpenSees assembles reactions over all nodes in a model, not just over the nodes that are constrained. When performing response history analysis, assembling reactions is likely not something you want or need to do at every time step. You probably just want … Continue reading Trying to Get a Reaction →