NaBloPoMo 2020 – OpenSees Edition

November is National Blog Posting Month, or NaBloPoMo. The goal is to write a blog post a day for the full month of November, and in doing so, engage readers and get the creative juices flowing. November is also NaNoWriMo (National Novel Writing Month), but we're talking about blog posts, not journal articles. Each day … Continue reading NaBloPoMo 2020 – OpenSees Edition →

The Basics of Frame Element Localization

Those strain softening constitutive models we like to use for concrete can lead to material nonlinearity that isolates, or localizes, in a single element or single integration point of your model. The resulting global response becomes non-objective, non-unique, or mesh-dependent. The objective of this post is to show the localization problem then describe solutions that … Continue reading The Basics of Frame Element Localization →

Glenn Holcomb, The Prof.

The Glenn Willis Holcomb Professorship in Structural Engineering was established at Oregon State University (OSU) in 2011 through a gift from the estate of Col. Roy C. Edgerton. While Col. Edgerton had an impressive civil engineering career, this post will focus on "The Prof." Glenn Holcomb joined the faculty at OSU in 1920 (when OSU … Continue reading Glenn Holcomb, The Prof. →

Closing the Loop on Direct Assembly

All structural engineering students learn the direct assembly method, where you fix all degrees of freedom (DOFs) in a structural model, then impose a unit value of displacement at and in the direction of the $latex j^{th}$ DOF in order to get the $latex j^{th}$ column of the stiffness matrix from the fixed-end forces of … Continue reading Closing the Loop on Direct Assembly →

How to Run an OpenSees Container in the Cloud

Now that OpenSees is just another Python module, you can do some pretty cool things in the cloud (and on the ground). One of those cool cloud things is running an OpenSees analysis in a container on Amazon Web Services (AWS) or Microsoft Azure. A KH-lenticular or Kelvin-Helmholtz wave cloud (from this tweet). With either … Continue reading How to Run an OpenSees Container in the Cloud →

Global Distributed Loads

Distributed loads on frame elements in OpenSees are defined with respect to the local element axes as opposed to global axes. This choice made the implementation easy, but it can give OpenSees users more shadow work, like bagging your own groceries or pumping your own gas. When global distributed loads act on inclined elements, e.g., … Continue reading Global Distributed Loads →

Thoughts After a Year of Blogging

Here are some random thoughts from the blog's first year. Prior to my first post, which was insubstantial and lame, I came up with about 45 ideas for posts of actual substance and saved them in my Drafts folder. Some of the ideas were, and still are, junk and will never be published. But, even … Continue reading Thoughts After a Year of Blogging →

SSI Modeling Challenge Results

After two modeling challenges (here and here) for the linear-elastic response of frame structures, I thought it would be a good idea to do a soil-structure interaction (SSI) modeling challenge. I feared the large uncertainty of geotechnical engineering relative to structural engineering would stifle participation, but I received four entries. Three participants submitted a single … Continue reading SSI Modeling Challenge Results →

Most Solvers Can Be Marplots

Have you ever tried to replicate the familiar beam stiffness coefficients $latex 12EI/L^3$, $latex 6EI/L^2$, $latex 4EI/L$, and $latex 2EI/L$ (there's a poem about them here) by imposing unit displacements and rotations at fixed supports? It should be one of the first sanity checks you make when using or developing new structural analysis software. You … Continue reading Most Solvers Can Be Marplots →