Hanging Sign
Hanging Sign
(OP)
I have a small job to design a steel mount for a hanging sign (approx. 40 lbs) that is a 36" octagon shape. This is something new for me so I thought I might post a few questions.
1.) Calculated the wind loads using ASCE 7-10 eqn. 29.5-1 and Figure 29.5-1. Since the sign is simply hanging down I'm wondering if it flapping around in the wind like a flag might trigger some additional dynamic loading case or scenario that my current static approach is missing.
2.) Any suggestion on structural eye-bolts (McMaster Carr ?). Granted the weight of the sign is relatively light but the "Home Depot" (lag) eye-bolts are somewhat questionable at first glance, I'm thinking to treat the hardware (bolts, chains etc...) as lifting gear (ASME B30.20-2010) with its associated safety margins. I can't seem to find anything in the ASCE related to this sort of thing, probably looking in the wrong place though. Perhaps the steel manual...
Below is a quick mock up of the design concept. Initially I thought to use pressure treated lumber but I think the welded rectangular HSS will give me a cleaner look.
1.) Calculated the wind loads using ASCE 7-10 eqn. 29.5-1 and Figure 29.5-1. Since the sign is simply hanging down I'm wondering if it flapping around in the wind like a flag might trigger some additional dynamic loading case or scenario that my current static approach is missing.
2.) Any suggestion on structural eye-bolts (McMaster Carr ?). Granted the weight of the sign is relatively light but the "Home Depot" (lag) eye-bolts are somewhat questionable at first glance, I'm thinking to treat the hardware (bolts, chains etc...) as lifting gear (ASME B30.20-2010) with its associated safety margins. I can't seem to find anything in the ASCE related to this sort of thing, probably looking in the wrong place though. Perhaps the steel manual...
Below is a quick mock up of the design concept. Initially I thought to use pressure treated lumber but I think the welded rectangular HSS will give me a cleaner look.
A confused student is a good student.
Nathaniel P. Wilkerson, PE
www.medeek.com






RE: Hanging Sign
Another option for your main frame is angles, it isn't as pretty but is cheaper and easier to build.
Machine Eye-bolts are usually rated with working load that includes a huge factor of safety. i would probably use a HD galvanized shouldered eye bolt. A 3/8" diameter has a working load of 1300#
RE: Hanging Sign
I'm actually surprised that the ASCE 7-10 does not have some sort of provision for "hanging" signs that differs from their other equations for signs, roof structures, lattices etc...
A confused student is a good student.
Nathaniel P. Wilkerson, PE
www.medeek.com
RE: Hanging Sign
I suppose ASCE 7 has the sign loading which is baisically what you have. the second benifit of yours is when it gets a force applied it sways thus reducing the exposed cross sectional area and less lateral load.
RE: Hanging Sign
I would rationalize that if you use the sign loads from ASCE7 they will be very conservative. Think about it, as the hanging size rotates/moves, the load is relieved in some capacity. If you design assuming it's rigid, I'd think you're good to go. As for dynamic increase, I wouldn't sweat it. If you have a 155 MPH wind, and that sign blows away, well, I don't think you'll get a call saying WHAT HAPPENED?
RE: Hanging Sign
A confused student is a good student.
Nathaniel P. Wilkerson, PE
www.medeek.com
RE: Hanging Sign
You might check around your area for similar signs that have been in place a while and consider that the more rigid the mount the more predictable the response.
RE: Hanging Sign
I would like to use the lower option because I think it will look cleaner than the upper option but I'm worried that with the marine environment the threads will corrode over time (5-10 years) and the eyebolt could pull loose. I intend on using stainless steel bolts, washers and nuts (all hardware will be stainless) so the upper option should be pretty much fail safe.
I'm also wondering if anyone has encountered any galvanic reaction between structural steel (ie. HSS, W sections) and stainless steel fasteners?
A confused student is a good student.
Nathaniel P. Wilkerson, PE
www.medeek.com
RE: Hanging Sign
I'm not to keen on either scheme - the top one allows rain water to penetrate the HSS tube at the bolt holes. The second one is not very easy to fabricate -
that rectangular cope is difficult to make without machining (ie it's an expensive step). You might check out a Crosby S-265 Weld-On Pivot Link.
They are simply welded on. I think they could be adequately protected from the marine environment with careful painting, same as the HSS material will require.
Regards,
DB
RE: Hanging Sign
I like the reasoning behind the use of the S-265 Pivot Link, I just wish they made one size smaller. I'll check McMaster Carr for a similar part but with a 3/8" link size.
I'm now revisiting the eye lag bolt issue that is currently installed into the wood sign (2 places). The ratings for these type of bolts is not good, at least not when compared to the machined eye bolts I was planning to install into the sign mount:
https://www.boltdepot.com/fastener-information/eye...
My main concern with this type of configuration is that the wood will eventually deteriorate over time and the lags will either corrode and snap, or fatigue and snap, or withdraw. The wood used for the sign is not pressure treated and will be exposed to a harsh rain/marine environment (washington peninsula, on the beach), everything made of wood rots out here. Painting helps but the rain just seems to turn it all into mush sooner or later.
I think the only way to reasonably suspend the sign is to weld a octagon frame of stainless steel channel (2x1x0.25) that clam shells the wood and has two eyebolt lifting points. Anything less than this will not be fail safe in this environment.
A confused student is a good student.
Nathaniel P. Wilkerson, PE
www.medeek.com
RE: Hanging Sign
Why not just weld a couple of lugs to the HSS with eyes for shackles or chain links, problem solved.
A confused student is a good student.
Nathaniel P. Wilkerson, PE
www.medeek.com
RE: Hanging Sign
For your frame, maybe have a steel sleeve that goes around just the top and maybe sides would be sufficient. Or maybe just a plate border on both sides to through bolt the wood? To some degree you cannot make it last forever if it stays wood. may offer plastic, fiberglass, metal???
To be honest, i so appreciate the way you think your problems through but i think this one is small enough that anything will work for 10+ years (wood at 10, steel at 50+). But i am still curious where you go with it.
RE: Hanging Sign
eye bolts replaced with welded lugs and shackles (SS), all of the connection hardware is now rated for 1000lbs+
DF No. 2 4x4 posts will be behind the two leg connection locations and the vertical leg.
A confused student is a good student.
Nathaniel P. Wilkerson, PE
www.medeek.com
RE: Hanging Sign
Very bad detail - water will be trapped in the channel. Drilling holes in the bottom channel would help, but it won't prevent water from being held against the wood by capillary action. Also, the threads on the stainless fasteners will probably gall and seize making life difficult for everyone.
Since you seem to have a good handle on the loads and forces involved, I would recommend that you consider bringing in a sign contractor to look at the project and let them suggest how they might fabricate a sign like this. Every shop has certain preferences in how they go about making their products. The two of you could save the client some significant dollars by designing something that can be economically fabricated.
Regards,
DB
RE: Hanging Sign
A confused student is a good student.
Nathaniel P. Wilkerson, PE
www.medeek.com
RE: Hanging Sign
"The real problem here is I am starting with a fabricated wood sign (non pressured treated) that will be exposed to a severe marine environment." Then why are you considering putting it in a frame that will ensure the wood edges are kept wet?
I'm only trying to point out some of the issues with the design and give you some ideas that have worked well for us on similar projects. You've come up with a expensive solution to a fairly simple problem.
Regards,
DB
NB: The SS fasteners are likely to seize going in; if they do, they'll have to drill them out. The locktite won't change this.
RE: Hanging Sign
A confused student is a good student.
Nathaniel P. Wilkerson, PE
www.medeek.com
RE: Hanging Sign
excuse the crude sketch without details, but you'll understand the essentials without doubt.
RE: Hanging Sign
A confused student is a good student.
Nathaniel P. Wilkerson, PE
www.medeek.com