Water Retaining Structures - Chamfer at Vertical Joints

[hopson175]

We are having an ongoing discussion related to the use of a vertical chamfer strip at construction joints in water retaining structures. This would look like a typical contraction joint without any interrupted reinforcement. There is a PVC waterstop cast into the construction joint.

I am in the midwest and have never seen this practice used. We have construction crews up this way from the south and apparently it is used in the there quite often and they are adamant it is required.

I do not like this detail as it reduces the concrete cross section and reinforcement cover at the joint, which to me is not desired in a water retaining structure wall designed as a 2 way plate. These structures have been designed using the most stringent min T&S reinf of .005 per ACI 350.

Is anyone familiar with this practice in water retaining structures?
Advantages to using this detail?
Disadvantages to using this detail?

Any thoughts or feedback would be appreciated.

Thanks

 

[BridgeSmith]

I believe that reducing the concrete cross-section is the point - to ensure that the section cracks where the waterstop is.

 

[hokie66]

The chamfered recesses are cosmetic. Not required or desired in a water retaining structure. Stick to your guns. This is not architectural concrete, it is industrial.

 

[hopson175]

Hotrod,

This is not a contraction/movement joint and I don't think it would really function as one with all the reinforcing going through the joint, i.e., cracking will still occur between the joints. For some specific situations we have designed true contraction joints in water retaining structures, but that is not what we are after here. That is the point of ACI 350 min reinf, to minimize the crack widths. 350 also requires greater reinf cover requirements to protect from exposure. Reducing the cross section reduces the cover to horizontal bars by almost half at the construction joint. Water stops are provided because there is a greater potential to crack at the construction joint and an almost guarantee to leak at a cold joint if no water stop is provided.

Hokie,

I'm assuming you don't see this as standard practice in your region. Can you give some additional explanation of why You don't desire this detail?, or if you disagree with the reasoning I've given?

Thank you both for the responses

 

[hokie66]

I completely agree with your reasoning, and didn't intend to argue against it.

 

[hopson175]

Thanks hokie..... I was just trying to pick your brain further.

 

[EDub24]

I’ve seen a similar detail here in CA with the diiffefence being a sealant is added to the chamfer. I think it might be a holdover from the pre-ACI 350 days to focus cracking where the waterstop is. It could also be a belt and suspenders detail. Have a sealant in addition to the waterstop to ensure leak protection.

 

[SlideRuleEra]

hopson175 - You have not mentioned wall thickness or chamfer depth. If wall thickness / chamfer depth >> 4, cosmetic... otherwise, probably intended to be functional.

Agree with hokie66 about cosmetic chamfer being out of place on an industrial structure. On all the projects I've worked on the reason is simple... no architect on industrial projects, do what makes sense not what (only) looks good.

http://www.SlideRuleEra.net

 

[BUGGAR]

Chamfer strips are frequently used by contractors to easily cover mismatched form joints. It's cheaper to throw up the forms and then fill the openings between panels with ripped material like chamfer strips. And you don't have the fins to bust off after the pour.