RC Column stirrups 2

[mar2805]

HI!
Can anyone maybe explain a benefit of using stirrups on the left instead the ones on the right?
Same column with 8 bars, except the right one has identical stirups shape and the one the left has 2 stirrups shapes.

 

[Trenno]

We're here to help you mate, a simple 'please' wouldn't go astray.

 

[Agent666]

Hi mar2805, I've never had a real world case in a column because in my opinion it's an inferior detail and my preference is for the outer stirrup to be one piece. This stems from a number of things, but one that people have not mentioned is that you're giving the ability for the two closed stirrups to move apart and violate covers on both end faces. At least with a single closed stirrup it can be detailed to achieve the cover all round, contractor still has to put it in the right location, but there's less opportunity to get it wrong.

You seem to be asking the same question over and over, which I believe I've tried to answer several different ways. So either I'm missing something obvious that you're after or you are missing something? If the below doesn't answer your question then please elaborate on what your particular concern is in more detail and someone else may be able to assist?

But here's an example of a wall detail from another engineer. Real world case looks exactly like your sketch but with sufficient lap length between the individual stirrups. In this case the bars were plain round bars, if they were deformed bars presumably the 450mm min lap could be halved.

 

[KootK]

@OP: it would be helpful to know more about you application. Where in the world will your project be located? Is this a high seismic, high ductility application?

Other comments:

1) For the case of overlapping tie sets, I believe that there will be many instances in which it will not be required to lap the neighboring ties. The first step with this, I feel, is to identify what job(s) it is that your ties are actually doing in your design. Often, as I would expect in OP's case, the ties are provided for confinement and vertical bar buckling only and are not intended to function as the wall horizontal shear reinforcing. When this is the case, shear is transferred across the length of the ties sets by horizontal bars that run either within the zone cage or outside of it, depending required ductility and local code rules.

2) Like others, I avoid overlapping tie sets, primarily, for reasons of constructability. Some not yet mentioned aspects of this are mentioned in the paragraph below taken from this article. For a relatively short zone like OP's I'm all about option in the figure below. For very long zones, especially prefabricated ones, I think that the best approach is to break the tie set into separate modules entirely and detail shear transfer between them as required.

 

[mar2805]

Guys sorry for the delay.
Agent666, thanx for posting your picture.
Im Eurocode based
I understand what you ment, but I think that your idea is more closely related to Shear Wall boundary elemnt detailing then to columns....but ok. I understand what you mean and I can agree with those hook overlapps, but then, we get to KookT figure 5C situation...So I think it would be better to provide one BiG external hook and then smaller "inner" hooks. The big external would be probably limited in lenght...for egsample in Europe, we never had hooks that were longer then 2 meters. That hook would enclose an shear wall boundary element thats approx 0,9m meter long.

 

[mar2805]

Guys can you see the picture attached.
Would you say that detailing in Case A and B is a poor solution for a shear wall boundary element?

 

[hardbutmild]

Since you're Eurocode based, I'll try to answer your last question. For DCM you need a stirrup holding a longitudinal bar at every 20 cm, and for DCH at every 15 cm. In case A you have a stirrup leg every 2s. If 2s < 20 (15) then it's okay, but i doubt it is. To me, kootk's example (b) seems like the best solution for walls considering both performance, simplicity and construction.