Tension connection

[aboallol]

hi,
My question has two parts:
1- I have abig cantilever 5m slab, so i had to use a diagonal column starting in the bottom of the main column and ending in the middle of the cantiliver, do I have to consider any moment in designing this diagonal member?
2- in case I considered only compression force in this member, I should add horizontal tension member in the slab, can any body give me a detail for the connection between the diagonal column and the tension bars?

 

[slickdeals]

In theory, your strut need not be designed for any moment, but a concrete structure being fixed will have moments (although not much is properly sized).

If you decide to use a bearing connection only at the slab, then the column will have to be designed as a sloped cantilever beam and there will be no moments at the slab-column interface.

Is there a reason you are using a concrete member for this strut?
Can you not have an embedded plate on the column and design a steel strut to pick up this load. That way you can have a pure compression member with no moments.

 

[aboallol]

Thanks (slickdeals) but in case I choosed steel strut, what will be the tension member in the slab, if you have any details for this connection (embeded plate) please send it to me.

 

[slickdeals]

The embedded plate will be designed for the shear due to the horizontal component of the strut compression force.

You don't specifically need any tension member in the slab. It is an interior connection on the slab, so you won't have any crazy edge conditions to worry about in shear.

Draw a sketch. It will become more obvious.

 

[slickdeals]

You can use reinforcing bars that are developed beyond the cantilever to transfer the tension into the slab.

 

[aboallol]

thanks again (slickdeals) for your reply, i have attached a sketch for what i understand from you please take a look and give me your opinion.

http://files.engineering.com/getfile.aspx?folder=895d997f-cf0c-4582-a196-8bbe383ad703&file=d.pdf

 

[slickdeals]

See attached.

 

[aboallol]

the back span is right, but what are the two red lines?

 

[slickdeals]

Move the embedded plates to the locations shown. Don't embed your HSS inside your slab. And have a face connection to the column directly.

 

[hokie66]

aboalloi,
By embedded, slickdeals means cast in. The normal way of doing this would be to locate cast in plates as he has shown, with headed studs as required to take the shear forces. After the concrete has been cast, and before the shoring is removed from the upper slab, install the strut. The connections could be site welded, bolted, or pinned (the latter two requiring tees rather than just plates).

 

[slickdeals]

Thanks Hokie for clarifying.

 

[hokie66]

No problem, slick. Didn't mean to butt in, but just thought with time differences...

 

[aboallol]

thank you all for your clarification, but i'm still asking about the tension in the slab, should'nt be there any connection (or some detail) between the slab reinforcement and the plate (or the bolts) to resist the tension?

 

[hokie66]

The headed studs on the plate take the horizontal reaction into the concrete. This horizontal reaction is then resisted by the slab reinforcement. If you are concerned that the top reinforcement serves two purposes and is beyond the ends of the studs, then provide enough reinforcement in the bottom to resist the thrust.