OpenSees Retractions

Citation cartels, peer-review rings, paper mills, and other schemes have eroded the integrity of scholarly publications. In some cases, articles can be retracted from journals; however, this outcome is rare. I set out to find if any OpenSees articles, i.e., articles that refer to OpenSees, have been retracted. Google Scholar is usually a good place … Continue reading OpenSees Retractions →

Is It Close Enough?

The locations and weights for Gauss-Lobatto beam integration, the de facto beam integration for force-based elements, are hard-coded in the OpenSees source code. For most cases in the LobattoBeamIntegration class, the locations and weights are written to only ten significant figures instead of 16 or more. Although I am certain that leaving six sig-figs on … Continue reading Is It Close Enough? →

Sloshing Around

With a Lagrangian formulation for fluids, the particle finite element method (PFEM) is ideal for simulating fluid-structure interaction (FSI) with all the solid elements and constitutive models available in OpenSees. The initial applications of the PFEM in OpenSees were simulations of tsunami loading on structures, where the fluid flow was gravity driven or based on … Continue reading Sloshing Around →

OpenSees Every Day

Using OpenSees as a direct object is common, e.g., "We used OpenSees to perform incremental dynamic analysis of reinforced concrete shear walls." That sentence was declarative and OpenSees was a noun. But OpenSees can also be a verb, in declarative and other types of sentences. Declarative I like to OpenSees every day. Interrogative Do you … Continue reading OpenSees Every Day →

Torsional Buckling

From time to time, I dabble with the OpenSees warping elements developed at the University of Sydney in 2011 for doubly symmetric sections, then in 2016 for open sections. Since my last foray into warping, I've taken the nonlinear displacement-based formulation from "it compiles" to "it works". Some other ancillary changes to the warping fiber … Continue reading Torsional Buckling →

Set and Get Concrete23 Response

When I wrote Concrete23, I copied Concrete01 then tweaked the unloading and reloading rules. I also added a couple of bells and whistles and it was music to my ears. But I wanted to record those sounds during an analysis. Recorders in OpenSees use the setResponse and getResponse methods to identify and obtain element, section, … Continue reading Set and Get Concrete23 Response →

All About Making that ZPA

On a recent project, I encountered a new term: the zero period acceleration, or ZPA. Of course it's a common term, just new to me. The ZPA is the peak pseudo-acceleration for modes of vibration whose frequency is very high relative to the input excitation. These modes respond in-phase, or quasi-statically, with the input excitation, … Continue reading All About Making that ZPA →