Hilti Anchors vs. Anchor Bolts 6

[Bedrock1977]

I know that Hilti makes a wide selection of different anchor systems. It seems that the traditional anchor bolts have been the design choice for all types of construction.

When it comes to residential, would you consider using Hilti anchors for anchoring the column baseplates to the supporting footing pads or are the traditional anchor bolts better for that? How about anchoring the sill plate to the foundation wall?

 

[H57]

Both can be acceptable if designed properly. I will generally allow for drilled and epoxied anchors for columns and sill plates. The size and embed depth will vary depending on the loads and conditions.

 

[eit09]

As H57 stated both are acceptable if designed properly. As for drilled and epoxy, I spech out the Hilti epoxy but just give the grade of anchor so customer has option to compare pricing between different anchor suppliers.

 

[archeng59]

I wish Hilti and other manufacturers had never invented the epoxy and adhesive anchors.

 

[msquared48]

Check the manufacgturer's fine print closely, as some afterset anchors are not suitable for vibratory loads, including seismic loads.

Mike McCann
MMC Engineering

 

[rowingengineer]

archeng59,
While I do agree these anchors are heavily over used onsite, they are very good option for cyclic/fatigue load conditions like wind, if you have to use a post-installed option. I like cast-in anchors the most.

I do not like to use mechanical anchors in wind applications due to the displacement in the concrete required to get ultimate strength conditions, and since you often have alternating loading conditions (ie tension to compression) mechanical anchors if loading past slip condition will fail very quickly.




When in doubt, just take the next small step.

 

[asixth]

With good workmanship cast-in anchors are preferred however we do get phone calls from builders who don't get them in the right position and then we have to go with the post-installed anchor option.

 

[BAretired]

archeng59,

Please enlarge on your earlier comment. Why do you wish there were no epoxy or adhesive anchors?

BA

 

[Bedrock1977]

Ok, I see now. What are some of the reasons for choosing the use a grouted base plate over a plate resting directly on a footing pad?

 

[Lion06]

The grouted baseplate allows the G.C. to get it level to accept the column. Rarely is the top of a footing level enough to accept a column properly.

 

[BAretired]

Grout also allows for minor adjustment of elevation.

BA

 

[boo1]

Biggest issues I see in residential anchor bolts are short bolts, and missing anchors in interior load bearing walls and high truss/girder uplift connection. Wish they were properly placed, but some times there missing.

 

[KCRatnayake]

In the region I'm practising, post-installed anchors are considered as somewhat expensive system than cast-in-situ anchors. But, in my openion, there are number of advantages you can gain when using post-installed anchors.

Advantages
* No need to do tedious setting outs. Just do the casting and then fasten. Cast-in-situ anchor positions might change during concrete operations
* Rapid construction. E.g. No need to keep starter bars from columns for lintels etc.

Disadvantages
* Close edge distance, distance between anchors etc. will reduce load carrying capacities
* Mechanical anchors exert pressure on base material when tightening
* Force-displacement curve is better in cast-in-situ anchors

There will be a bigger list.....


KC

 

[archeng59]

BAretired, because contractors will purposely omit installing anchor bolts because they want to use the post-installed anchors instead. Those products certainly can be used, but the workmanship issues are horrendous and the anchors are rarely installed properly. Also, contractors regularly want to omit dowels for CMU walls and use the epoxy/adhesive to install the dowels instead of using cast-in-place dowels.

 

[BAretired]

archeng59, I don't recall running into that problem in fifty years of practice. If anchor bolts are shown on the drawing, the contractor has always installed them. But when a bolt is required in existing concrete or the bolts are installed incorrectly, the adhesive anchors are very handy.

BA

 

[Ron]

Considering the quality of residential construction as compared to commercial construction, the lack of training of the individuals doing the work, and the tendency of residential contractors to not understand structural necessity, I would stay away from expansion or epoxy anchors for such applications.

Make them put in the anchor bolts properly. Get really stubborn once or twice and have them tear out a footing and re-place the concrete if the bolts don't align...they'll learn how to do it right eventually.

Use leveling nuts and good grout for the baseplates. Keep in mind...residential contractors don't know diddly about steel erection...be prepared to hold their hands a lot.

 

[JoshPlumSE]

I understand where Archeng59 is coming from. In the industrial world we deal with a similar issue related to epoxy anchors. But, that's usually related to conflicts between the design schedule and the construction schedule.

We may not have the final equipment drawings yet. We may not even know which vendor is going to provide the equipment. Yet we are asked to provide final foundation drawings under the assumption that they can go ahead and pour the foundations as long as they can go back and use the post-installed anchors to correct for any issue.

It's a bit more stressful to have to rely on that sort of thing. (hence the sympathy with ArchEng59). But, it also allows us to absolutely impress clients with our ability to meet a demanding schedule.

Josh

 

[archeng59]

BA, all I can do is speak about my own experiences. Ron, I have required that the contractor remove and replace misplaced anchors or to install the cast-in-place anchors shown on the drawings. The contractor goes crying to the owner that I'm delaying the project with unreasonable requirements because Hilti's products can be used. When the owner calls and demands that I approve the epoxy/adhesive anchors so it won't delay his date of occupancy, what can I do except explain why I don't approve them? Not much. I then require that a special inspector observe the installation and provide a report. For some reason, this scenario has occurred several times on more than one project during the last couple of years. And not just on my projects, as I'm finding out. Aggravating.

 

[Ron]

archeng59...I agree with you! Most of the time you don't have the luxury of being an a$$, but it sure is nice when you can get that point across. Yep...it's aggravating. Contractor always sounds better to the owner than we do.

 

[hokie66]

Another vote cast with archeng59. If not for post-installed bolts, contractors would have to actually take some care in setting out their cast in bolts. There are a lot of reasons post-installed bolts are not as good as cast in. Drilled in bolts depend heavily on installation workmanship and inspection, while cast in bolts just have to be in the right place. Most epoxy bolts are subject to creep (Big Dig tunnel ceiling).