RAM Frame Unstable Structure

RE: RAM Frame Unstable Structure

Seth Guthrie — Wed, 16 Sep 2020 20:56:43 GMT

The program's wind load generation for big buildings with small low-roof areas is limited. The program will load the low roof with windward and leeward pressure which can be too much. See: https://communities.bentley.com/products/ram-staad/w/structural_analysis_and_design__wiki/2052/ram-frame---wind-loads-faq

The frames perpendicular to the load will take some small amount of the lateral force in this case since the columns are continuous through 2 stories. You could pin the columns vs. weak axis bending at the bottom of the top story to alleviate that.

RE: RAM Frame Unstable Structure

Patrick Westerkamp — Wed, 16 Sep 2020 15:07:09 GMT

Seth, thank you for the information. I have gone through my model and made some adjustments, but am still not getting the results I would think are correct. It appears the loads are not being distributed properly (even when I use a rigid diaphragm). An exterior frame line is not receiving any of the wind loads. It looks like the frames that are perpendicular to the wind load are taking the loads. I uploaded my file to the secure file upload. Thanks!

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RE: RAM Frame Unstable Structure

Seth Guthrie — Mon, 14 Sep 2020 22:39:13 GMT

Sounds like you have a semi-rigid diaphragm. I sometimes coach people to increase the deck thickness and turn on the out-of-plane stiffness when that's needed for stability.

See: