handex
Structural
- Jul 1, 2010
- 56
Hi Guys,
Just hoping somebody could shed some light on how they would figure out the effective length of a sign post such as the one shown in the attached sketch. The only lateral restraint is provided by the adjacent column, and linked together by the intermediate framing members. We do quite a lot of these signs, however generally the client wants to use square or rectangular hollow box sections for aesthetic reasons, and even using conservative values for the effective length the member capacity usually just ends up being the section capacity (buckling is no issue). For the few signs we have done of these where the client wants I section posts, we usually make conservative assumptions and try apply some common sense judgement, but I cant help but think there has to be a more precise way to calculate the effective lengths.
Our thinking is that the effective length that should be used for design will be governed by the stiffness of the intermediate members connecting both the post and also the end connections, and lie somewhere between the lengths C and H as shown on the sketch. The closest I have come to finding any technical info is by searching "lean on" systems, but I still couldn't find anything that would apply. I assume the buckling is more so based on the entire 2D system, but trying to model that in a structural program for the purpose of designing relatively small signs seems like the old analogy of using a sledgehammer for nails. If anyone has any ideas of simple methods or rules of thumb it would be much appreciated.
Cheers
Just hoping somebody could shed some light on how they would figure out the effective length of a sign post such as the one shown in the attached sketch. The only lateral restraint is provided by the adjacent column, and linked together by the intermediate framing members. We do quite a lot of these signs, however generally the client wants to use square or rectangular hollow box sections for aesthetic reasons, and even using conservative values for the effective length the member capacity usually just ends up being the section capacity (buckling is no issue). For the few signs we have done of these where the client wants I section posts, we usually make conservative assumptions and try apply some common sense judgement, but I cant help but think there has to be a more precise way to calculate the effective lengths.
Our thinking is that the effective length that should be used for design will be governed by the stiffness of the intermediate members connecting both the post and also the end connections, and lie somewhere between the lengths C and H as shown on the sketch. The closest I have come to finding any technical info is by searching "lean on" systems, but I still couldn't find anything that would apply. I assume the buckling is more so based on the entire 2D system, but trying to model that in a structural program for the purpose of designing relatively small signs seems like the old analogy of using a sledgehammer for nails. If anyone has any ideas of simple methods or rules of thumb it would be much appreciated.
Cheers
