Attaching tension cable to concrete block wall
Attaching tension cable to concrete block wall
(OP)
I'm doing some charity work that involves putting a wire rope under tension between two block walls.
I can't find anything down and dirty on this subject.
Can someone point me in the correct direction?
Specs.
>12" block walls
>distance between walls is 60'
>load on cable is 350# max. with possible doubling of weight due to shock.
> plan to sandwich blocks between steel plates with eyebolt thru center.
> 3/8 DIA. wire rope is available.
ATTACHED IS A QUICK SKETCH
I can't find anything down and dirty on this subject.
Can someone point me in the correct direction?
Specs.
>12" block walls
>distance between walls is 60'
>load on cable is 350# max. with possible doubling of weight due to shock.
> plan to sandwich blocks between steel plates with eyebolt thru center.
> 3/8 DIA. wire rope is available.
ATTACHED IS A QUICK SKETCH





RE: Attaching tension cable to concrete block wall
Then you need to determine pull-thru strength of the concrete block. And overturning resistance of the block wall. And probably a few more things I'm forgetting.
I notice you posted here instead of the structural engineering forum...
RE: Attaching tension cable to concrete block wall
Anyway, the tension in the cable has to support half of the maximum shock load+any temperature effects+wind+settling of the walls+all the other excellent suggestions you will receive in this thread.
The simple answer is T*sin(theta)=V/2 where theta = atan(centre deflection under max load*2/span), so paradoxically the greater the unladen sag the easier the job (except that your shock loads will probably increase).
If human beings are ever anywhere in the vicinity think about using a factor of safety of more than 10.
Also see the thread on snapping winch cables, being tickled by a 60 ft bight won't make anybody happy.
Cheers
Greg Locock
SIG:Please see FAQ731-376: Eng-Tips.com Forum Policies for tips on how to make the best use of Eng-Tips.
RE: Attaching tension cable to concrete block wall
So I'd contemplate-
-A vertical strong back attached to floor and upper deck.
-Surface bonding both sides of the wall, floor to ceiling, for maybe 4 feet either side of the attachment.
RE: Attaching tension cable to concrete block wall
RE: Attaching tension cable to concrete block wall
RE: Attaching tension cable to concrete block wall
The cable size had gone down to 1/4" (got into sag) and is still oversize, may go down to 3/16".
I also decided to go with a steel cross member and attach to trusses. While the load I'm sure would be ok on the blocks, with bonding plates. I know how to figure the steel beam factors and loads.
Thanks for the great advice,
Mark
RE: Attaching tension cable to concrete block wall
RE: Attaching tension cable to concrete block wall
If the wall is not reinforced and grouted, then you have to be concerned about pull-through on a block. If that's the case, make sure your backing plate engages more than a single block.
Since you have a 12-inch masonry wall, it is likely to be reinforced and grouted. Further it will have better shear resistance in the mortar-block interface.
If you consider that you have about 96 square inches of mortar bond contact for each block (8x16 block, inside face mortar and outside face mortar, joint at least 1" wide on block contact shell....before someone yells at me, I'm not talking about the thickness of the mortar joint which is 1/2" to 5/8"), and even if you consider a minimal shear bond strength of 25 psi, you have a resistance of 2400 lbs.
Your backing plate needs to be larger than the core of the block, so your plate needs to be at least 8"x8".
RE: Attaching tension cable to concrete block wall
In summary, it's all about the wall, not the wire rope. If you know how that the wall is reinforced and core filled, fine. If not, don't do it. There are far too many kids killed each year because well-meaning fathers have hung a basketball goal on an unreinforced section of masonry.
RE: Attaching tension cable to concrete block wall
Ron I'm sure you are right and if absolutely necessary I'll look at this again but feel that I would rather spend a few extra bucks and stay in my safe zone.
chico I work with steel everyday and have designed buildings so I'll be ok there but thanks.