Other than state-of-the-art material and geometrically nonlinear frame element formulations, it's fair to say OpenSees is not known for its breadth of structural finite elements like quads, bricks, and shells. There are solid elements for geotechnical applications and fluid elements for fluid-structure interaction via the PFEM, but what's the story on shell elements in OpenSees? … Continue reading OpenSees Shells by the Seashore
Unretiring the String Class
If you've compiled the OpenSees source code, you may have noticed the SRC/string directory, whose two files, G3string.h and G3string.cpp, implement character strings as first-class objects, complete with overloaded operators and deep copies. G3string is based on the String class, which I used for programming projects in my undergraduate computer science courses. In the G3string.h … Continue reading Unretiring the String Class
An Update of the IMK Models
Hysteretic models include several parameters that can be fit to a variety of physical phenomena known to occur in steel and reinforced concrete members under cyclic loading. I did my Ph.D. in the Bay Area, but not at The Farm. Accordingly, I'm more of a fiber section aficionado--but I get the appeal of hysteretic models. … Continue reading An Update of the IMK Models
Algorithmic Limerick
There once was a post-doc named Dave,Who ran OpenSees in his cave.Non-convergence, 'bout to miss dinner,He switched the algorithm to 'Linear'.Just think of all the trouble he saved. Although I changed the name and circumstances to protect the guilty, I have known more than one person who, when faced with convergence problems in OpenSees, decided … Continue reading Algorithmic Limerick
Thankful for OpenSees
Thanksgiving is this week, which means campuses across the US will be pretty quiet. Monday through Wednesday should be a boon for faculty seeking "big blocks of time" to write. Let's hope they feel inspired. Come Thursday, we'll reflect on what we're thankful for. Family, friends, and health are perennial list toppers for me. In … Continue reading Thankful for OpenSees
Just Another Python Module
When OpenSees got off the ground, many finite element analysis software packages relied on fixed format input. So, it was important to integrate OpenSees with a fully functional scripting language to give users flexibility in creating applications without requiring users to write and compile C++ main() functions. I don't remember all the factors that went … Continue reading Just Another Python Module
OpenSees Time Machine
I recently found two Zip disks in my office. They were the next big thing for about 15 minutes in the late 1990s and early 2000s. I then got my hands on an external Zip drive and was able to offload the disks' contents. One disk has lecture notes and assignments from a few graduate … Continue reading OpenSees Time Machine
Only Their Mother Can Tell Them Apart
In January 1999, when OpenSees was known as G3, Prof. Fenves created G2 for teaching nonlinear structural analysis in CE 221 at UC Berkeley. G2 was written in MATLAB with an architecture similar to G3. I took CE 221 and used G2 for the homework assignments, but after a few years I lost the code. … Continue reading Only Their Mother Can Tell Them Apart
OpenSees Source Control: From Zip to Git
Back in the G3 days, when there were essentially two developers, Frank kept the source code up to date on a Zip disk that he stuffed into a cargo pocket of his pants each afternoon. Frank instructed me to retrieve the disk if he was ever hit by a bus. As long as the buses … Continue reading OpenSees Source Control: From Zip to Git
Gaming ResearchGate
I think ResearchGate is a good resource. It's in the mix with LinkedIn and Twitter on the spectrum of social networks for academics to disseminate their research. As an external reviewer for promotion and tenure cases, I have seen achievements from ResearchGate included in candidate dossiers. I find this dubious because it's quite easy to … Continue reading Gaming ResearchGate
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