SSI Modeling Challenge

I know enough soil-structure interaction (SSI) to be dangerous. This means I'm no expert in the subject, only someone who is capable of describing an SSI modeling challenge. The subject of this challenge is the soil-bridge model shown below. The model is based on research by a former M.S. student and a couple colleagues in … Continue reading SSI Modeling Challenge →

Results of a New Challenge

After proposing a modeling challenge for linear-elastic analysis of a strongback frame, I proposed a second challenge for linear-elastic analysis of the Ziemian frame. There were eight participants in this challenge, an increase from five for the first challenge. Due to the light gravity loads on the frame, whether or not the analysis included self-weight … Continue reading Results of a New Challenge →

Not Just a Modeling Term

Master/slave is common terminology to describe relationships in many technical fields, e.g., between tables in databases or between devices in control systems. The terminology also appears in finite element analysis where the response of one node controls the response of another node through constraints. However, this terminology is based on archaic relationships within our society. … Continue reading Not Just a Modeling Term →

A New Challenge

The results from a previous modeling challenge were excellent with 100% of entries correct. But before we deep dive into the dark world of modeling nonlinear structural response, let's do one more challenge with linear analysis. The frame model shown below is UP50HA from a series of low-rise industrial structures whose reliability under gravity loading … Continue reading A New Challenge →

Semi-Blind Kind of Contest Results

I proposed a simplified model of a strongback frame system as a modeling challenge and five people took the bait. I am happy to report that all five computed the expected roof displacement of 0.0128 mm, give or take 0.0001 mm. Good job, everyone! Having given this problem as an OpenSeesPy assignment for a couple … Continue reading Semi-Blind Kind of Contest Results →

A Semi-Blind Kind of Contest

Contests where researchers and practitioners blindly predict the response of structural systems have produced some rather interesting results. And by "interesting", I mean "all over the place". So much so, that in an effort to protect the contestants, the contest organizers rarely make the results publicly available. Nonlinear structural analysis is hard though. Even with … Continue reading A Semi-Blind Kind of Contest →

OpenSees Time Machine

I recently found two Zip disks in my office. They were the next big thing for about 15 minutes in the late 1990s and early 2000s. I then got my hands on an external Zip drive and was able to offload the disks' contents. One disk has lecture notes and assignments from a few graduate … Continue reading OpenSees Time Machine →

Only Their Mother Can Tell Them Apart

In January 1999, when OpenSees was known as G3, Prof. Fenves created G2 for teaching nonlinear structural analysis in CE 221 at UC Berkeley. G2 was written in MATLAB with an architecture similar to G3. I took CE 221 and used G2 for the homework assignments, but after a few years I lost the code. … Continue reading Only Their Mother Can Tell Them Apart →

No CAPS When You Spell the Framework’s Name

MF DOOM is one of the greatest lyricists--of any genre--that you've probably never heard of. In his 2004 track "All Caps" with Madlib, DOOM explains how his stage name should be written. All CAPS when you spell the man's name. MF DOOM, 2004 The preferred capitalization of OpenSees is not so clear. I often see … Continue reading No CAPS When You Spell the Framework’s Name →