RE: Steel Beam with Opening Failing but Report & Interaction is OK

Shaun B — Tue, 22 Sep 2020 15:05:48 GMT

Thank you for the quick reply.

In the first case, I checked the W14x22 beam with a 3" diameter opening and had an interaction ratio of 1.25. Then I made the opening 6" diameter and the interaction ratio was 0.98.

If I'm understanding you correctly, the program is checking the top tee compression strength. Because the 3" diameter opening had a larger top tee depth, this is probably causing a buckling failure of the tee web and would cause the higher interaction ratio than increasing the opening to 6" diameter?

RE: Steel Beam with Opening Failing but Report & Interaction is OK

Seth Guthrie — Tue, 22 Sep 2020 14:53:51 GMT

For the case I saw recently the details are below. If the same situation does not fit your case let me know.

Version: 17.01.01.05

Strength ratio indicates something greater than 1 (e.g. 1.20), but there are no warnings and nothing in the design report looks like a problem (that I see).

The failing interaction should not have been included in the list of interaction checks. There is an exemption for checking tees for buckling capacity strength when the tees have an aspect ratio less than 4. Tees in the beam met this exemption, however the they were still checked for strength and one tee did fail the strength check… So we have a situation where an exemption masked a real strength check.

Since the tee was not to be considered for a buckling strength check, there was no need to include its ratio in the list of interaction ratios considered in determining the worst interaction.

The messaging did not flag the warning because it wasn’t required but the method for looking up the worst interaction considered it when it should not have. Alternative, wherever the check was made, there should have been a recognition that the interaction was not needed and set appropriately so that the interaction did not matter at the end of the design process.

Will be corrected in the next update.