Steel brackets to hold bench seat up

[Dirty Doogie]

Pulse - would you get 20mpa out of bricks?

I was going to suggest knocking the mortar out of the corner of a few bricks and inserting 50 x 50 x 8 mm angle steel into the brick work and repointing with epoxy mortar. But there are too many variables to be sure it would work.

I have fitted wall mounted a laminated beam benchtop (Weight approx 120 kg) into a standard brick wall by knocking out a row of bricks - making a metal plate with extending arms from angle section and then epoxy mortaring the whole missing brick section. The benchtop was 2400 long and has been carrying about 1000 kg (I stored bags of gyprock stuff and cement on it)

[Pulse]

true.... better overengineer then

but then again that's the fun in DIY... do it so well that it obviously wasn't a real builder...

Pulse

[frogger]

Thanks MrFixIt, Pulse and Dirty Doogie. I think ill use 10 to 12mm dynabolts to be safe. Not sure if I will take out bricks etc as DD mentioned. Ill see how it goes with the 2 "L" brakcets suggested by MrFixIt and DJ . Just one more question do you feel this bench will need 3 brackets or 2 should be fine ?

[DvdHntr]

200kg is very light. That is less than 2 people in engineering terms. You also have to take into account that the weight will come on as an impact and may be at the edge of the seat so that will create a moment. The ratio of the distance between your bolts to the width of the ratio of the loads. Also, I would make it 250kg or 2.5kN and muliply that by 1.2 for the dynamic action to give you a total imposed load of 3.75kN And then the ratio of the 560mm to the spacing of the bolts will increase the load again. The actual weight of the seat will be assumed to act at 560/2 (280) away from the wall so the ratio must be used for that weight. And then adding the two loads will give the pull out force but you must multiply that by 1.3 as it is a prying force (just an engineering requirement). You then can divide by the number of brackets to get the required load per bolt in tension. The shear load will be the sum of the loads without multiplying by the ratio.
If you are using the limit state design tables by ramset the seat load is muliplied by 1.2 and the person load by 1.5.

Check out ramset and Hilti as they have different connectors for hollow and cored filled brickwork.

If I have confused you then please tell me.

[MrFixIt]

Hi

A 6mm dynabolt only 25mm embedded into 20Mpa concrete has a tension working limit of 2200 N or about 220kg per anchor. Depending on the size of the bracket two of these should be plenty...

In a perfect world yes

That is CONCRETE, however into the mortar between the bricks is severely lacking in grip. Consider that there will most likely be some depth lost due to the finish of the mortar joint rolled or raked etc.

Concrete generally is a good mix and the chances of gaps around the dynabolt in concrete are much less than in a (potentially quickly built) brick wall.

There are pros and cons of using mortar or bricks in which to mount the dynabolt - this has been discussed at length in another thread somewhere on this forum.

If *I* was mounting this bracket and seat, I would use 10mm dynabolts and drill into the mortar. The reasoning behind this is that *if* there are gaps in the mortar you will at least obtain some grip between the layers of brick. Fastening dyna bolts into the brick runs the risk of drilling into the (manufactured) holes in the brick - in which case you may get NO grip at all!

Frogger, I missed the comment about you wanting the seat to appear "floating".

If access to the other side of the double brick wall is readily available and it is not too much of a problem to work on or "patch up" etc, A potential alternative for you then is this...

Buy a long 10mm masonry drill, long enough to drill through both leaves of the double brick wall. Purchase some 50mm x 10mm flat bar and use this to support your seat.

Drill (or otherwise) create a 50mm high x 10mm wide slot in the double brick wall. This slot is to go all the way through both leaves of the db wall. Insert the 50mm x 10mm flat bar into these (vertical) slots so we now have two pieces of 50mm x 10mm steel flat bar on edge to support the seat. Obviously you will need to cut slots in the seat for these pieces of flat bar to pass though.

Obviously these slots will be MUCH easier to create in the perpendicular mortar joints. This will (most likely) mean that you will need to add some additional timber to your seat to which you can fasten the flat bar, as it is unlikely that your seat timber "ends" will line up with the mortar joints.

You can use a piece of flat bar - cut in to a long "wedge" shape to clean up/remove the mortar from the drilled holes, to help create the "slot" required

When the steel is in position and held there by some convenient means (your choice). Mount the seat and bolt/screw into the flat bar. The seat will really appear to "float" and will exceed your wildest expectations for load carrying capacity

See rough sketches below

HTH
.

[DvdHntr]

I would create a frame with a 100x100x6EA into the wall and a series of angles welded on under the seat perp. to the wall and a trimmer length at the other end. But you are going to need a really solid connection. The other solution would be to drill through the double brick and put a series of bolts with large washers.

[Ivan in Oz]

G'Day,
Just wondering what was the result with the mounting of the seat.

[frogger]

Hi Ivan,

Well as you could imagine this time of year takes everyone a while to get back to work. Im seeing someone next week about making the steel brackets. When I all have it put together Ill post a picture of the seat / master peace.
Thanks
Frogger

[DvdHntr]

Hi Ivan,

Well as you could imagine this time of year takes everyone a while to get back to work. Im seeing someone next week about making the steel brackets. When I all have it put together Ill post a picture of the seat / master peace.
Thanks
Frogger

I hope you took my advice and went with a much heavier connection.

[frogger]

Well I finially got the brackets made and they work well.
Might be hard to see as I have put one coat of paint on but they are extremely strong.
Thanks for everyones help

[DvdHntr]

They do look quite strong.