Uniaxial, or one-dimensional, material models are the work horses of OpenSees. Originally developed for the truss element, these models have proliferated thanks to fiber section models. However, because they are simply scalar functions, UniaxialMaterial models can be used in several other contexts. The calling function knows the context, not the UniaxialMaterial model--it only provides an … Continue reading Uniaxial Multi-Tool
OpenSees Fire v2.0
OpenSees modules for thermal loading and thermo-mechanical behavior were developed by Usmani et al in the early 2010s. This was the first foray for OpenSees outside its earthquake engineering comfort zone and highlighted the benefits of an open, collaborative software framework--an opportunity for the research community to share modeling methodologies, develop new applications, and ensure … Continue reading OpenSees Fire v2.0
A Little Secret About OpenSees Tcl
Putting load and fiber commands inside braces {} preceded by pattern and section commands, respectively, was a conscious choice in the early days of G3/OpenSees. section Fiber 1 { patch ... layer ... fiber ... } pattern Plain 1 Linear { load ... eleLoad ... sp ... } The intent was to enforce the same … Continue reading A Little Secret About OpenSees Tcl
The Linear Algorithm Strikes Again
This post on the OpenSees message board reminded me of another reason not to 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
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