Blockwork Wall with 3 Tonne object hanging from side of wall 1

[Sparkes1992]

Hi Guys,

Ive got a blockwork wall 4 meters in height and its supported a 3 tonne object bolted into the side of the wall at half its height. I'm guessing this will place quite a large concentrated moment onto the wall. I'm not 100% sure about how to go about designing this wall to deal with this moment. I'd say that im going to need quite a bit of load on the wall in order to generate enough friction force for the mortar to stop bricks from locally getting pulled out. Any help/guidance on this would be much appreciated.

 

[XR250]

Lots of rebar in a grouted wall with thru bolts (preferably). Also, your connection to the structure at the top (and diaphragm) will have to resist the moment couple in addition to wind and seismic.
Make sure you know the center of gravity of the object to calculate the moment.

 

[OldBldgGuy]

Your question is a little vague; is the 3 tonnes a plate 150mm thick bolted to the wall or a jib crane with an engine hanging 2m away? Serious bending of masonry walls is a special consideration, but an eccentric load is much more easily dealt with. Either way you need both vertical and horizontal reinforcing. You said blockwork in your first line and "stop bricks from locally getting pulled out" later; to me those are 2 totally different systems. Blocks are easy to reinforce and grout to achieve bending resistance in both directions, brickwork is essentially only reinforceable for horizontal bending.

 

[BAretired]

You may want to reinforce the wall with a pilaster each side of the 3 tonne object.

BA

 

[Sparkes1992]

My apologies, it's pretty much an eccentric load acting on wall

 

[hokie66]

What XR250 said.

 

[Sparkes1992]

So basically I should be right just checking the moment generated by this object vs the moment capacity of the wall. Is there anything else in particular that I should be looking st?[pre][/pre]

 

[KootK]

Is this a brick wall or a concrete masonry block wall? 8"? 10"? 12" thick? One or two layers of vertical reinforcing? What s the load eccentricity?

Designing the wall for flexure, shear, and axial load is important but designing the connection to the wall will probably be critical, as you rightly anticipated. And yes, whether or not you pull a block out of the wall, or yank a cone out of a block, will be very important. I'd recommend posting a sketch of your proposed connection detail so that we can provide meaningful help with that.



I like to debate structural engineering theory -- a lot. If I challenge you on something, know that I'm doing so because I respect your opinion enough to either change it or adopt it.

 

[wannabeSE]

Is there anything else in particular that I should be looking st?

Aside from the moment and the connection of the new equipment mentioned by others, everything should be checked. I suggest you talk to a mentor or senior engineer at your office. Often times, an experienced engineer can look at many aspects and deem it OK by inspection. Without that experience, every aspect of the wall design needs to be checked as well as the foundation below and any connection to the structure above.

 

[kipfoot]

I can't help but wonder whether the 3 ton object is an AC condensing unit.

It's all good advice above regarding the bending capacity of the wall and its attachments. I'll also suggest that the support assembly for the object be designed to keep the vertical distance between connection points as large as is practical, so that the pull-out on the upper connection is minimized.

 

[XR250]

I can't help but wonder whether the 3 ton object is an AC condensing unit.

Well at least his design would be conservative as these only weight about 700 lbs.

 

[BAretired]

Ive got a blockwork wall 4 meters in height and its supported a 3 tonne object bolted into the side of the wall at half its height. I'm guessing this will place quite a large concentrated moment onto the wall. I'm not 100% sure about how to go about designing this wall to deal with this moment. I'd say that im going to need quite a bit of load on the wall in order to generate enough friction force for the mortar to stop bricks from locally getting pulled out. Any help/guidance on this would be much appreciated.

I think more information is needed. A sketch might help.

BA

 

[Sparkes1992]

Thanks for all of the great responses guys.


I'm on the road at the moment so won't be able to provide a sketch. However, what I've got is an EXISTING 390mm x 190mm Unit Concrete block wall. The owner wants to essentially bolt a rack of powerlifting weights (see picture below). I want to design the wall assuming that it is unreinforced ( apologies I should have mentioned this in my first post). I guess my main concern is pulling out a block due to the tension force. How do I check this? I've checked the moment capacity of the wall, shear etc.

 

[Sparkes1992]

 

[hokie66]

If it is indeed unreinforced, I would recommend that you provide a vertical steel or timber member behind the bracket, extending and connected floor to floor, and connect the bracket to that.

 

[XR250]

That rack does not appear capable of supporting 3 tons

 

[dik]

Run a channel up either side with a member across the bottom of the unit and support the channels at the top and bottom. Assuming an e of 1', you have a 3.3 'K moment (tonnes and 2 channels) and with connection at top and bottom, assumed 9' apart, you have a horizontal loading of about 300 or 400 lbs applied at the top of the wall and the base. Should be doable...

The bracket shown, as noted, does not appear to be anywhere adequate.

Dik

 

[XR250]

It is probably only adequate if it has 4 bolts at each pipe to reduce the bending length of the plate. Have to take that localized couple account for the bolt loads as well if you don't add supplementary steel as dlk posted.
I'm not sure how he is getting 3 tons, however. That rack looks only capable of holding 6 or so 45 lb. plates on each pipe.

 

[IngDod]

I have seen unreinforced CMU walls resist all kinds of crazy things, I once saw one wall where the first three rows of blocks (the wall was 3.5m wide with concrete columns at each end) had been taken out and the entire thing (3m tall) was held together solely by the mortar (The one is not supposed to have any tension capacity). But I live in the third world so these things are fairly common and apparently the laws of physics don’t apply here. My advice, don’t depend at all on that wall. Try to erect an independent structure, perhaps an HSS tube embedded in the wall, or a channel with its own foundation.

 

[dik]

6600 lbs is like hanging a Cadillac from the wall... needs a little something, even is parked close to the wall... it's a big load.

Dik