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.

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

Your DLL Might Be Ignored

I am not a fan of DLLs (dynamic-link library) for material and element models in OpenSees. There are many technical reasons for my dislike of DLLs--fragile code, multiple versions swirling around online, keeping up to date with the latest OpenSees executable, debugging difficulty, and cross-platform compatibility to name a few. So, if you've published your … Continue reading Your DLL Might Be Ignored

You Get What You Give

In the early days of OpenSees, conventional wisdom was "You get what you pay for". Sure, the internet was around, but the only OpenSees resources were the wiki, the examples manuals, and the message board. Those resources are still around today. But there's a ton of other OpenSees resources available including packages, pre- and post-processors, … Continue reading You Get What You Give

Eigenvalues During an Analysis

How to compute the eigenvalues (natural periods) of a structural model during an analysis, as the stiffness changes due to yielding, unloading, reloading, large displacement, etc., is a common question. In general, periods elongate during yielding events, then shorten again upon unloading. The extent and duration of period change depends on the constitutive models and … Continue reading Eigenvalues During an Analysis