This post on the OpenSees message board reminded of another reason not to ever use the Linear algorithm, even when you have a linear model. Some elements need that second iteration in order to record all of their response. Not only shellMITC4 mentioned on the message board, but also the beloved forceBeamColumn. If you define … Continue reading The Linear Algorithm Strikes Again
Make Room for Storage
In a previous post, I showed how equation numberers can reduce the bandwidth of the tangent stiffness matrix. In addition to reducing the solution time for linear systems of equations, a smaller bandwidth reduces the data required to store the tangent stiffness matrix. To discuss matrix storage in this post, I'll use the frame model … Continue reading Make Room for Storage
OpenSees Thanksgiving
Happy Thanksgiving everyone! Even if you don't celebrate Thanksgiving, I'm thankful that you're here reading the blog. Last year's Thanksgiving post was a little preachy. This year, I simply want to reiterate that I'm thankful to have been a part of OpenSees from the beginning. Some exciting things are happening with OpenSees right now and … Continue reading OpenSees Thanksgiving
OpenSees Facebook Group
I've been answering questions on the OpenSees message board lately. Mostly responding with quick answers, nothing that requires me to download or copy/paste scripts to run locally. A friend suggested I drop in on the OpenSees Facebook group to answer some questions. The group has been around since 2008 and has over 3,000 members (not … Continue reading OpenSees Facebook Group
Compiling OpenSees
In the early days of G3/OpenSees, I was in change of compiling the Windows version using Visual C++, part of Visual Studio. Frank maintained the Linux version. Pretty soon after arriving in Eastchester, I switched to compiling OpenSees on Linux and periodically compiled in Visual Studio--only when I absolutely had to do so. Visual Studio … Continue reading Compiling OpenSees
Reduce Your Bandwidth
For large structural models, the solution to $latex {\bf K}_T\Delta {\bf U}={\bf R}$ can be the computational bottleneck during an analysis. Although computing speed and algorithms to solve $latex {\bf K}_T\Delta {\bf U}={\bf R}$ are very good, you still want to make sure the solution happens as quickly as possible, particularly when inside the double … Continue reading Reduce Your Bandwidth
Moving and Influential
OpenSees is probably not the first, or second, software you think of when you need to generate influence lines or perform moving load analysis, e.g., across bridge girders. However, Tcl and Python scripting capabilities make OpenSees ideal for this type of analysis. To keep things to the point, I'll show an influence line analysis for … Continue reading Moving and Influential
Twitter Bot 200
The OpenSees Twitter bot I created, the one that likes and retweets any tweet with the hashtags #OpenSees or #OpenSeesPy, passed the 200 follower mark recently after just under a year in service. The bot's mission is to share with the Twitterverse all the cool things people do with OpenSees. Some day I'd like to … Continue reading Twitter Bot 200
Mass and Weight
Many structural analysis software programs will automatically define mass based on the input gravity loads. OpenSees is not one of those programs. You have to define mass and weight separately. Fortunately, using variables for units makes the mass and weight definitions easy. Plus, if using customary units, you won't have to waste time Googling the … Continue reading Mass and Weight
Rigid Joint Offsets
The geometric coordinate transformation objects handle rigid joint offsets for frame elements in OpenSees. This is nice because the code for the transformations of displacements and forces is not duplicated in the element state determinations. There are three things to keep in mind when using rigid joint offsets. First, the offsets are global with respect … Continue reading Rigid Joint Offsets
