# Stability Challenge Results

I posted a modeling challenge for the famous, perhaps now infamous, three member truss example of OpenSees. The members are very slender, so I wanted to see how well we can account for geometric nonlinearity. First, the results. There were five entries--three reported a load factor of about 0.47 and two gave a load factor … Continue reading Stability Challenge Results

# A Very Stable Challenge

With linear structural analysis, a number is a number. However, reality starts to creep in when physics dictates that you need to account for nonlinear effects. The three member structure shown below is a perfect example--Example1.1.tcl, one of the most OG OpenSees examples. Have you ever paid attention to the member sizes though? If so, … Continue reading A Very Stable Challenge

# 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

# 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

# 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