Concrete Column Tie Details 1

[eit09]

I have attached a sketch of my detail in question. Basically I have an existing 24" steel pipe that will be filled and encased by concrete. The pipe must remain in place so the detailing of the ties is not a normal detail. The vertical bars are #10's and all the ties are #4 bars. I looked around but was unable to find any similar details. I also checked ACI (7.10.5.3) and believe this arrangement satisfies the code requirements. Looking for comments and/or concerns with this type of detail.

 

[wiktor]

Your ties looks very small when compared with the main (#10) reinforcement. I would prefer having min. 20% of main reiforcement as ties, or just follow typical column reinforcement priciples.

 

[eit09]

Thanks for the reply but the steel pipe in the center of the column restricts me from using typical column reinforcement principles. Just to clarify, So you prefer to have your tie quantities to be at least 20% of the total amount of vertical reinforcement Quanity?

 

[csd72]

eit09,

Have you looked at the strength of the composite section in this one? Are these bars required for strength or just for serviceability?

If the latter only then I wouldnt worry toomuch, but if they are required for strength then they need to be properly restrained with at least the same size as the code requires.

Just remember that as these bars are at 45 degrees then they are not as effective as perpendicular bars.

Have you considered doing a circular tie to pick up the intermediate ones?

 

[BAretired]

Are the square ties on the exterior made from two "U" shaped ties? Otherwise, you have to thread them on over the end of the pipe.

The short diagonal ties do not provide good retention of the vertical bars against buckling out. I would prefer to see an octagonal ring, but for the same reason as the square ring, it has to be placed in two pieces.

BA

 

[eit09]

csd72,
I thought I would ignore the pipes contributed strength and desing the reinforced column to take the load. The column is only about 50% stressed. Circular ties would be ideal but unfortunatly we cannot place the ties from the top of the pipe only from the sides.

BAretired,
yes, there are two exeriour u ties as our placement of ties is limited. The existing pipe is supporting a conveyor that must stay in service while we pour this column. The 2 piece octagonal would be great but per ACI I do't believe we could assume lateral support for the verticles.

 

[wiktor]

Yes, I would like to have 20% of the total vertical reinforcement as ties.

 

[BAretired]

eit09,

I don't use ACI, so I'm not sure why the octagonal ties cannot be used. What is wrong with the detail shown attached?

BA

 

[eit09]

ACI states that every corner and alternate longitudinal bar shall have lateral support provided by the corner of a tie unless the clear distance between verticles is 6" or less. The spacing in the sketch is greater than 6".

 

[frv]

It doesn't have to be a 90 deg. corner. It can be up to 135 deg.

 

[BAretired]

In the case of an octagonal tie, each angles is 135⁰, so it appears to meet the ACI criteria.

BA