Concrete tie beam 1

[hello12345hello]

A steel braced frame columns are supported on Spread Footing with tie beam between the columns. I have vertical and horizontal reaction from Frame. So designing tie beam i have to consider that has regular concrete beam with axial load (Horizontal reaction from column) ?

 

[BAretired]

That is correct.

BA

 

[hello12345hello]

That axial load acts as compression or tension so for axial compression its like column axial capacity. And for axial tension i will check required Steel area = Pu/(phi*fy)?

 

[BAretired]

It is a tension member, not compression. The only function of the concrete is to protect the steel. You should check your reinforcement for strength, making sure you have sufficient lap at required splices. You should also consider the amount of strain in the tie and how it affects the performance of the frame. You may wish to limit the strain by using a conservative value for tie stress.

BA

 

[JAE]

That is how I would do it.

 

[hello12345hello]

How can i check amount of strain in the tie. I have 2'X 2' beam with 8#6 for axial load of 100 kip.

 

[hokie66]

Tie members don't have to be wrapped with concrete, but they do have to be protected. Something like Denso tape is one way. Whether or not in concrete, I prefer to use couplers rather than lapped bars.

 

[BAretired]

Couplers are a better detail, I agree.

If you are carrying 100 kips with 8-#6 bars, your steel area is 3.52 in^2 and the stress is 28,300 psi. The total strain is E*L/28,300 where L is the length of the tie.

BA

 

[hello12345hello]

To check footing design i have to check for max load case (Max Vertical load and max Hori. Load) on footing to check for overturning and sliding both ? And i have to check also for Min. Load case (min load case - uplift and hori. load) on footing for overturning and sliding. ?

 

[PUEngineer]

Maybe I missed something, but why does everyone think this is a tension tie? The original post said this was a tie beam for a braced frame.

 

[BAretired]

Perhaps the OP can clarify whether the force in the tie beam is tension, compression or either/or.

BA

 

[hokie66]

To me, the word "tie" is synonymous with tension member. If it is a compression member, it would be called a strut.

 

[hello12345hello]

how about footing design for sliding.

 

[BAretired]

hello12345hello,

how about footing design for sliding.

Well, how about it?

Is the tie beam a tension member, a compression member or both? Perhaps you should post a sketch of your structure so that we can get a better understanding of the problem.

BA

 

[hello12345hello]

tie beam acts as tension or compression depends upon loading from wind or seismic load direction. And top of concrete beam is same as top of footing.

 

[BAretired]

Provide a sketch.

BA

 

[hello12345hello]

attached is rough sketch for that.

 

[hello12345hello]

If its unclear i will repost it.

 

[hokie66]

Sketch comes through a bit dark. Anyway, if it is a compression strut sometimes, it would be designed as a column for that load case. And yes, you have to resist both the horizontal and vertical components of load. Sliding resistance, passive resistance, resistance by floor slab are all possibilities for the horizontal component.

 

[ahmedhegazi]

what is the dimensions of your beam and footing?