KL/r > 200 - Greenhouse Posts
KL/r > 200 - Greenhouse Posts
(OP)
I understand that it KL/r "preferably" should not exceed 200. In greenhouse design, the columns are inherently slender and the factor often exceeds 200. In some cases they exceed 300. Since greenhouse structures typically move much more than a typical building and have a high degree of redundancy, logic seems to suggest that a column with a KL/r of 300 should not be that great of a concern, especially since so many greenhouses are out there and performing under the design load conditions. One reason for a high factor is when K is assumed to be 2 (pinned base and top fixed Rotationally with a truss). Does anyone have any experience or comments regarding this situation?






RE: KL/r > 200 - Greenhouse Posts
RE: KL/r > 200 - Greenhouse Posts
RE: KL/r > 200 - Greenhouse Posts
1) check to see if the farm building code has different allowable slenderness requirements (if applicable to farm sites/ low occupancy);
2) your boundary conditions may be a little conservative in that often a gutterconnected greenhouse structure has posts which are set in a concrete foundation. This condition is closer to a fixed end condition rather than pinned.
3) as previously mentions, watch out for initial imperfections in the alignment.
jetmaker
RE: KL/r > 200 - Greenhouse Posts
DaveAtkins
RE: KL/r > 200 - Greenhouse Posts
In the ASD (9th Edn.)section E1 refers to B7 which refers to you to use equation E2-2 if slenderness is >200..
RE: KL/r > 200 - Greenhouse Posts
RE: KL/r > 200 - Greenhouse Posts
RE: KL/r > 200 - Greenhouse Posts
The DAM relies on the engineer's ability to do an ACCURATE second-order analysis to capture instabilities. In this case, he needs to be able to capture both types: P-LittleDelta and perhaps P-BigDelta.
RE: KL/r > 200 - Greenhouse Posts
RE: KL/r > 200 - Greenhouse Posts
RE: KL/r > 200 - Greenhouse Posts
I was introduced to all that effective length stuff about 15 years ago and have been using it pretty steadily ever since. I've even taught it once. There are still weird cases that come up and I have no clue what to do with. I say Good Riddance ELM, probably the most misused part of the steel Spec.!