Replies

1. 
   florida | Apr 22, 2010 04:16pm | #1

   That is only 34 pounds per piece of all thread. Even cantilevered out 9 inches it would still be less than 40 pounds per piece. I don't see any problem with it.  If it makes you nervous use 8 pieces instead of 6 or bump up to 3/4 inch.

2. 
   bigdog | Apr 22, 2010 05:50pm | #2

   Factors Affecting Connections

   About half dozen factors here:

   1. Direction of loading (assume 90 degrees to the rod)

   2. Duration of load (assume long term)

   3. Condition of use (assume the worst, since un-known)

   4. Net section calculations (1/2" or 3/4" data from steel manual)

   5. Number of fasteners in a row (un-known exact configuration, grid or line?)

   6. Horizontal shear in members at a connection (200# / 6, not a problem in shear)

   That being said, deflection is probably the least of you problems, (every thing deflects some) I'd be more worried that there would be a long term corrosion / rust incident / accident, especially if it's an overhead sign. Number 3 above.  Espescially if in a marine environment, with salt air.

   But FYI, For one single bolt. it's deflection would be based on:

   Fixed End (in brick) Cantilevered Beam - Concentrated Load at Free End, sort of, discounting number 5 above.

   Therefore : deflection, delta,Max = P x L(cubed) / 3EI, in the appropriate units.  won't be jack, say about <1/8 inch, guessing.

   I'd be asking the Arch Man about anti-rust / corrosion protecting, then if the sign falls on some one in 2016, your covered.

   The first advise on going over size helps too, it won't have a rust or corrosion problem as soon.

1. 
   cwcjr09 | Apr 23, 2010 08:30am | #4

   Ok. I feel better after all that.

   I think I'll go with 3/4 for peace of mind and stainless steel for some corrosion protection.  

   Fastener  vertical orientations is: (2) 2 1/2" from the top, (2) in the center, and (2) 2 1/2" from the bottom - all spaced 2 1/2" from the edge of the sign.

   The load is 90 degrees to the all-thread and the sign will be hung on a wall about 5' off the ground (with the top being 14' off the ground).

   Thanks for all the info.

1. 
   Clewless1 | Apr 24, 2010 11:25am | #7

   I agree w/ Florida. 1/2"

   I agree w/ Florida. 1/2" steel and supporting only 40 lbs max perpendicular to the rod over 9 1/2" distance. Doesn't sound like much.

   Also I'd be hesitant to second guess a licensed designer. That's what the license is about. If there is any failure, he's on the hook ... assuming you install per the specs. Why have him design it if you are going to second guess him and throw the design in the round file?

2. 
   cussnu2 | Apr 28, 2010 03:54pm | #26

   The 1st thing that came to mind was will the wall support it?  I've seen brick walls on buildings that were lucky to be hold themselves up....and many of them that didn't.  Of course, I'm picutering this going on an old building not brand new.

3. 
   DanH | Apr 22, 2010 07:50pm | #3

   With that cantilever the real threat is the brick failing and releasing the rod.

   But I would think the strength of different grades of all-thread is well known.  If nothing else, ask the engineers who designed the walkway for the Hyatt Regency in Kansas City.

1. 
   [email protected] | Apr 23, 2010 10:25am | #5

   Don't Diss the Design Engineers

   The rod failures at the Hyatt Regency weren't caused by poor design. 

   It was poor construction.  Somebody decided that the really long rods, with threaded ends were really too expensive to manufacture and transport, and that they could couple shorter rods together, and the idiot construction engineer/inspector decided that was fine without consulting the designer. 

   Problem was the couplers had an offset in them, so the load put amoment on the rods at the connectors, and as the rods were loaded and unloaded, they flexed there.  The flexing lead to fatigue hardening, and cracking.  When one of the rods finally failed, the shock load from that failure then caused the rest to fail. 

   Most of the really spectacular failures that are attributed to engineering, are actually poor construction.  Something that was drilled into me while I was in college working on a degree with an emphasis in construction engineering. 

1. 
   DanH | Apr 23, 2010 07:41pm | #6

   You're right it was poor design, but the rods didn't fail.  Rather, the anchorage points pulled through the beams.

   Ultimately the problem was that the engineers produced an unbuildable design, so the builder did what "made sense", without verifying the modifications first.  And the designers apparently did no on-site checks to make sure things were built to spec.

   In the OP's situation I'd be most worried about the rods pulling out of the brick.  Brick, in particular, is a very unpredictable medium in which to anchor things.

4. 
   junkhound | Apr 24, 2010 03:46pm | #8

   IMO,

   anyone who would specify or use threaded rod in bending is incompetent.

   Also, what about Wind load?   You happen to be in any tornado or hurricane area? 

1. 
   cwcjr09 | Apr 24, 2010 06:34pm | #9

   "anyone who would specify or

   "anyone who would specify or use threaded rod in bending is incompetent." 

   ......could you clarify that. not exactly sure what you mean with the "in bending" part. Just curious.

   Thanks

    

1. 
   DanH | Apr 24, 2010 08:20pm | #10

   I assume he means with shear loading.

2. 
   Clewless1 | Apr 24, 2010 10:25pm | #11

   Maybe he should have said 'shear'? The way it was described implied a bending application ... force perpendicular to the steel rod rather than tension/compression that are along the length of the rod. It is a cantilever condition as opposed to a 'beam like' condition (i.e. supported on two ends) ... so maybe it is shear only? I forget these details of my structures training (which is OK since structural engineering isn't my profession).

5. 
   gfretwell | Apr 24, 2010 11:23pm | #12

   If you sleeved that all thread in 1.5" pipe nipples and pulled it up tight it would be a whole lot stronger than the rod itself.

   That would virtually eliminate the bending moment.

1. 
   DanH | Apr 24, 2010 11:30pm | #13

   That would virtually eliminate the bending moment.

   Or pull the rods out of the brick.

1. 
   gfretwell | Apr 25, 2010 02:02am | #14

   If the brick is that unstable, it is probably not suitable to hang the sign from in the first place.

1. 
   Clewless1 | Apr 25, 2010 02:16am | #15

   Which is why you have the architect to design it. He assesses the condition for its appropriateness.

2. 
   DanH | Apr 25, 2010 09:24am | #16

   By inserting the pipe and tightening against it you're increasing the pull-out force on the brick maybe 10x.

1. 
   gfretwell | Apr 25, 2010 11:09am | #17

   I agree you are prestressing the connection but what do you think the force is when that sign starts whipping in the wind if you don't? Maybe I am just hurricane oriented but you can get 50-60 MPH gusts just about anywhere

2. 
   junkhound | Apr 25, 2010 01:25pm | #18

   To OP.

   Print this thread out an leave it on the archy's desk. 

   If the brick is pre-1955 brick, ti will likely hold, esp if old paving brick <G>   Heck, most here nowadays probbly never even held a paving brick.....

   If new china import brick (is there such a thing) or the EPA mandated firing type of brick, I'd not prestress an epoxy insert in pullout either. 

   This old FHB site has surely gone downhill, a year ago some concrete and brick experts would have chimed in, they just stay away now.  

   In my humble hubris (oxymoron??), somebody has ta keep the yokels from killing thselves or the customer's customers.  <G>

3. 
   DanH | Apr 25, 2010 03:35pm | #19

   Even without prestressing, if the pipe does it's job it adds considerable additonal thrust load.  Worse in a windstorm.

4. 
   gfretwell | Apr 25, 2010 05:51pm | #20

   I thought the concern was to prevent bending the rod and causing it to fail from fatigue. I would never install anything on a rod used like that in the frst place. Why not fabricate a bracket that adequately transfers the loads? 

5. 
   DanH | Apr 25, 2010 07:16pm | #21

   I thought the concern was to prevent bending the rod and causing it to fail from fatigue.

   Some may have been concerned about that, but you can't ignore all the other concerns in order to deal with that one.

   There is no reasonable doubt that the rod suggested is sufficient to carry the load, but if it flexes too much that will eventually loosen the fastening into the brick (long before the rod fails from fatigue).  So the rod needs to be oversized, but how much so is hard to judge.

   Why not fabricate a bracket that adequately transfers the loads?

   A bracket with knee braces would be ugly.

6. 
   junkhound | Apr 25, 2010 07:17pm | #22

   Why not fabricate a bracket that adequately transfers the loads? 

   AMEN - give the man 4 dog biscuits!

   edit - remember just as the post key was hit that the correct terminology was/is  "milkbones" !!  Or not recalling correctly yet. ?

7. 
   DanH | Apr 25, 2010 07:43pm | #23

   I'll point out that the yield strength of the rod is not what needs to be determined here.  Rather, some way to estimate the amount of deflection in shear that can occur in the rod is the issue.  Consider a 80th percentile wind load to be 200 pounds per rod, you'd like the rod to bend less than (thumb suck) 1/8" in the 9.5" of exposed length.

   Now if you can determine the modulus of the steel I'm guessing there's a formula somewhere to determine deflection.  I could probably dig one out of my old CRC handbook, but I'm too lazy.  But there's some good stuff here that even does the job for round beams:  http://www.clag.org.uk/beam.html

   δ = FL³/3EI - is the basic formula, where I for a round section is Pi x diameter to the 4th power / 64.  E is the modulus and F is the applied load.  The article gives a metric modulus of mild steel of around 210.

   Figure the rod has a root diameter of 10 mm, and the exposed length is 250 mm.  The applied force (not weight) is 91000 grams multiplied by G which is 9810.

   I'll leave it to someone else to do the math.

8. 
   [email protected] | Apr 26, 2010 03:05pm | #24

   Make the Architect make the decision.

   I heartily recommend that the Architect be teh one who does all the sizing, and that you insist on a detail from them to keep yourself covered. 

   The Architect should be carrying error and omisssion insurance.  So, if they screw up and something catastropic happens, they are covered. 

   If you design it, and something happens, how much do you think you'll have left after it goes through court? 

   You can loose everything you own, due to one decision to design and build something.  The responsibility is the Design Professionals, that is why we make the big bucks. 

1. 
   Clewless1 | Apr 28, 2010 08:03am | #25

   I totally agree ... He's designed it. He has the responsibility. If you have a good reason to second guess his design, then get another professional opinion. Our comments don't mean much ... food for thought at best. We haven't seen the situation or the design. The OP has little or no idea who we are and what our knowledge base or experience is.

   The E&O insurance of the architect is there for a reason. The OP alters the design and he buys the responsibility.

9. 
   Jeff_Clarke | Apr 28, 2010 09:15pm | #27

   I would use or design a bracket to hold the sign (with a gusset from top to bottom) and Hilti fasteners to attach the bracket to the brick.

   http://www.hilti.com/holcom/page/module/product/prca_rangedetail.jsf?lang=en&nodeId=-11025

   There is a company in Northern Virginia that will make up custom stainless clips and brackets very reasonably.