Column Link Design 2

[strawhats2000]

Hi all,

I have 3 questions regarding Column Link/Binder/Lateral Ties design (Here applicable code is BS8110).

1. What is the basis for selecting a single restraining link or an enclosed link for intermediate bars in a column when clear distance between those bars are > 150 mm?

2. Given that min bar spacing is 75 mm., how come we can have 4T12 (12mm. Bars) in a 150x150 Column (which is normative in my country). This leaves a bar spacing of 54 mm (150-(Bar:12x2)-(Cover: 30x2)-(Link 6x2)) much less than code requirement of 75 mm.

3. How to design link for Corner Column 400x400. I have seen many engineering side proposing 2 nos. Enclosed Links at right angle to each other with 4T12 at the intersection and 2T12 at each remaining corners. Please check drawing.

4 Does any one has any notes regarding design of lateral ties or links for Column?

Thanks.

 

[KootK]

1. What is the basis for selecting a single restraining link or an enclosed link for intermediate bars in a column when clear distance between those bars are > 150 mm?

I go with the single, candy cane links in almost all instances. They are much more constructable than internal Hoops in my opinion.

2. Given that min bar spacing is 75 mm., how come we can have 4T12 (12mm. Bars) in a 150x150 Column (which is normative in my country). This leaves a bar spacing of 54 mm (150-(Bar:12x2)-(Cover: 30x2)-(Link 6x2)) much less than code requirement of 75 mm.

I coulndn't say. 150 mm here seems like a constructability problem. I try not to uses two layers of reinforcing unless my walls are at least 250 thick. Even 200 is pretty congested.

3. How to design link for Corner Column 400x400. I have seen many engineering side proposing 2 nos. Enclosed Links at right angle to each other with 4T12 at the intersection and 2T12 at each remaining corners. Please check drawing.

Congestion issues aside, this sounds fine. Usually the link design is based on the code minimums for longitudinal bar buckling prevention. In some cases, design is governed by shear capacity and/or ductility requirements.

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.

 

[hokie66]

Those 150 thick vertical elements are just too difficult to construct, in my opinion. How do you compact the concrete? I haven't worked in a country where these skinny concrete columns are used, but have seen the results when travelling. Not good.

 

[KootK]

For columns, it may also be worth investigating the fire rating implications of such a small column. Some codes punish columns smaller than 8" for this reason.

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.