I thought wet setting anchor bolts was bad practice?

[wijgeng]

As I mentioned in my title: I thought wet setting anchor bolts was bad practice?

We are building drilled piers (30" diam. X 20' deep). There are four anchor bolts embedded in the center of the pier. The anchor bolts are 1" diameter by 2.5' long, headed anchors. The sub contractor, unsurprisingly, wants to wet set the anchor bolts. My company's standard specifications specifically request that wet set embedment not be used. For my own understanding, I wanted to see if ACI had any input on this. I went to ACI 336-01 "Specification for the Construction of Drilled Piers" and found section 3.8-Placement of anchorage embedments. The section states, "Place anchorage components either by pushing into fresh concrete or by setting in the open shaft. If the anchorage components are not easily pushed into the fresh concrete, the concrete shall be vibrated to ensure full contact between anchorages and concrete." Does this mean ACI endorses wet setting? Or do they only endorse the practice in the case of drilled piers? Does ACI give any other guidance on anchor bolt embedment?

Thank you!

 

[KootK]

Fascinating. I was under the same impression as you: wet set = bad. Somewhere along the way, I'm pretty sure that someone has shown me testing indicating sub par performance of wet set rebar dowels. I'm sure that capacity has a lot to do with how quickly the dowels get set but then that's tough to police.

If tension capacity is importent to you, maybe generous rod lengths or
the use of a pile cap element would be prudent.

It must be a terrible pain to pour concrete into the piers with an anchor bolt template in the way.

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.

 

[wijgeng]

It is difficult, but there is a 10" diameter hole in the template ring so it is possible. What they have been doing is pouring the pier without the bolts until they reach the top 3 ft or so. Then they set the anchor bolts and finish it off. They are still shifting the anchor bolts after concrete is poured though which, in my opinion, could act to debond the bolts.

Thanks for your response and input!

 

[TehMightyEngineer]

I would personally interpret that ACI says that wet setting the anchors is acceptable for drilled piers, but only for piers.

From the Structural Engineering Association of Utah (SEAU) as reported on this blog

http://kimballeng.blogspot.com/2009/11/wet-setting-anchor-boltsholdowns.html

(I was too busy to find the original):

"IBC Section 1912 states that anchors shall be designed per Appendix D of ACI 318, where even the preliminary “Definitions” section calls out an “Anchor” as either being “cast into concrete” or “post-installed into hardened concrete”, and not listing “wet setting” as an option. Even more clear is the definition of “Cast-in Anchor” in the same section, where it states “installed before placing concrete” (italics added). IBC Table 1704.4 calls specifically for the periodic inspection of “reinforcing steel, including … placement”, but calls for continuous inspection for “bolts to be installed in concrete prior to and during placement”. IBC 1704.13 also states that unusual “Materials and systems required to be installed in accordance with additional manufacturer’s instructions that prescribe requirements not contained in this code” shall require special inspection. Section 109.3.1 calls out that “any required reinforcing steel is in place” prior to foundation inspections, and section 109.3.2 states that “other ancillary equipment items are in place … before any concrete is placed” below slabs. While none of this states “anchor bolts” or “holdown straps” tied into place, the intent seems obvious.


The IBC does have exceptions to the special inspection requirements in section 1704, primarily for “minor” work or for “Group R-3” residential construction. But even in the IRC, Section R109.1.1, it again requires that “any required reinforcing steel is in place and supported prior to the placing of concrete”. If the reinforcing is required to be in place prior to inspection, it only seems a natural extension that the IRC also intends for anchorages that rely upon the strength of this adjacent reinforcing to also be in place prior to inspection and placing of concrete.


As interpreted from the code, SEAU recommends that all embedded anchors and other hardware for IBC governed construction be firmly supported and tied into place prior to pouring of concrete, or that the placement of these anchors is continuously special inspected as they are being “wet set”. We also recommend this same interpretation be used for embedded light gage straps and other undefined anchors. Light gage holdown straps and other similar anchors are no longer considered “unusual”, but they certainly do carry with them “additional manufacturer’s instructions” for careful installation, and are normally a part of the seismic force resisting system. The action of tying all anchors into place before pouring, rather than allowing “wet setting” of anchors during pouring, helps to insure proper consolidation of concrete around the anchor and thus proper structural action of the anchor as it takes structural loads. Most Engineers, as well as most Building Officials, have seen the voids often left to one side or the other of a “wet set” bolt or dowel or strap – sometimes obviously reducing it’s structural capacity and increasing liability to the Engineer, Building Official, Owner and Contractor. When embedded dowels, bolts and straps are “wet set” we would recommend that a randomly selected portion of these embedded hardware are pull tested to full rated capacity prior to acceptance by the Engineer or Building Official."

Maine Professional and Structural Engineer.

http://www.fepc.us

(Just passed the 16-hour SE exam, woohoo!)

 

[TehMightyEngineer]

Also, see ACI 301 section 5.3.1.3.

Maine Professional and Structural Engineer.

http://www.fepc.us

(Just passed the 16-hour SE exam, woohoo!)

 

[Leftwow]

Down here in Louisiana we've got some extreme weather in the summer. I asked my superior about this situation, he was exclaiming how fast the concrete can dry in the summer. He said there was one instance where they actually wet set the anchor bolts, they had to pound the anchors in with a hammer. Sounds kind of ridiculous to me.

 

[wijgeng]

Thanks for all of your statements. I think it is clear that wet setting is frowned upon, but thought it was interesting that ACI 336 designates wet setting as acceptable for drilled pier construction. Thanks again!

Playswow, what a crazy story!

 

[dhengr]

Wijgeng:
If they can’t vibrate the conc. around the A.B’s. after wet setting them, they shouldn’t be wet setting them. Otherwise, they just can’t assure good consolidation of the conc. around the A.B’s. and good bond with the A.B’s. This thinking should apply to all A.B’s. not just those in piers, and it should apply to any hardware embedded in conc. intended to carry structural loads. And, the idea that this is the way my Grandad showed me to do it, is a bunch of b.s. in today’s construction and codes world. TME did a good job of summing things up.

 

[JLNJ]

It seems like every project has anchor bolt setting issues.

If the bolts are not too highly stressed, then you might allow wet setting IF the contrator has a good plan to make sure the bolts are in the right location and set to the right height.

I can't count the number of calls I've received regarding mis-set bolts!

 

[TehMightyEngineer]

I can't count the number of calls I've received regarding mis-set bolts!

This is actually my biggest reason to not wet set. Capacity issues caused by wet setting follows in a close second.

Maine Professional and Structural Engineer.

http://www.fepc.us

(Just passed the 16-hour SE exam, woohoo!)

 

[JAE]

Just detail a pier cap over the top of the pier. The anchors are then set prior to the cap concrete being placed.

The tie between the pier and the cap is simply the pier vertical reinforcement which can extend upward above the concrete cutoff elevation and just below the top of the cap.



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