Gimme All Your Damping, All Your Mass and Stiffness Too

Just because OpenSees is open source does not mean it is a fully transparent box. This is mostly because documentation has lagged behind development. So, pessimists would say the box is semi-opaque while optimists would characterize it as semi-transparent. But a few parts of OpenSees are definitely housed in an opaque box. Take, for instance, … Continue reading Gimme All Your Damping, All Your Mass and Stiffness Too

More Is Not Always Better

I sometimes run across simulations where frame member response is computed using displacement-based beam-column elements with more than two Gauss points per element. These elements require at least two Gauss points to ensure a complete solution and to capture the exact solution for a linear-elastic, prismatic member. While it is well known that you can … Continue reading More Is Not Always Better

A Tale of Two Element Formulations

The question of whether to use the force-based or displacement-based formulation for material nonlinear frame analysis is one that comes up a lot. The answer depends on a few factors, mostly the material and the element length. To get a sense of the basic issues, I will compare the two element formulations with a numerical … Continue reading A Tale of Two Element Formulations

Behind the Elastic Interior

If VH1 expanded its list of the top one hit wonders of the 2000s to include journal articles in structural engineering, Scott and Fenves (2006) would be right up there with James Blunt and Gnarls Barkley. Actually, Google Scholar puts the article up there with some pretty nice company. Like all journal articles, there's something … Continue reading Behind the Elastic Interior

Is Plastic Hinge Integration a Fruit or a Vegetable?

If distributed plasticity elements are fruits and concentrated plasticity elements are vegetables, then plastic hinge integration is something like a tomato. Based on papers I've read, manuscripts I've reviewed, presentations I've seen, etc., there's some confusion as to whether plastic hinge integration is a fruit or a vegetable. Here's my two cents. Concentrated plasticity elements … Continue reading Is Plastic Hinge Integration a Fruit or a Vegetable?