Design of dowel bar depth when going into existing concrete

[Brandnew]

I had such good answers on my first question I have a second already.

When working with concrete (or masonry) retrofits or repairs, how do you figure the development length for the dowel bars that are inserted into existing concrete??

Is this something that you can only get from the epoxy/adhesive manufactures? Or is there a way to design this? I would feel more comfortable if I could design it myself.

Is it me or does what you really need to know get left out in school?

Any comments or good books appreciated.

 

[Qshake]

The basics and then some (for graduate students) are learned in School - these can be applied to everyday situations that we deal with. Frankly, there is already a lot a student has to learn without cluttering thier minds with pull out strengths.

The industry staple for this application is the PCI handbook. In this reference you will find the various modes of failure for this dowel application. The modes include but aren't limited to bond failure, dowel yield and concrete(masonry) shear cone pull out, etc. The latter is the brunt of the PCI handbook section regarding the shear cone failure. There are many applications - single pullout, multiple dowels closely spaced, dowels spaced close to an edge etc.

The material is fairly basic and easy to understand if you have the reference at hand. If not its worth having around the office, so check out PCI on the internet.

Good Luck.

 

[Ingenuity]

I agree with Qshake in that the PCI handbook is a good resource for this and many other applications - worth the purchase if you do not have it.

From a construction aspect, if you are specifying rebar to be doweled into existing concrete you may also consider some nominal testing on critical elements that justify such. Add something on your drawings/specifications/notes re this. All too often field personnel do NOT install these well, and some inspection/testing/QC check is required IMHO.

The preparation and installation of overhead dowels, for instance (especially large diameter bar) into existing concrete can be quite challenging. From hole depth, hole diameter, hole clean out and prep, epoxy install then rebar install - many things can go wrong - and for an inspector visiting after the installation it is possibly too late.

 

[ishvaaag]

Yet for what I remember the PCI book deals mainly with headed bolt inserts placed in precast parts.

It is common the need of use inserts without such heads, coming in adhesive and mechanical fastening ways.

The UBC 94 deals with inserts in masonry without head in 2108.1. I made recently a freely available worksheet for this procedure in mathcad that you can get in its collaboratory, civil engineering folder.

Respect inserts in general, went largely modestly regulated in Europe. The apparition of an ETAG document on anchors already available in pdf format for download may mark an end to this.

In any case, hilti and maybe others have excellent software for this purpose entirely free.

 

[Ingenuity]

ishvaaag,

Can you post the internet/download link to the ETAG document on anchors - for pdf format, as you discussed in your post. Thanks.

 

[DMWWEngr]

Hilti has some nice resources on this. A downloadable program (although I think it's only good for 30 days??) and a lot of technical data sheets on the products offered.

To Ingenuity:

Here's a link for a program with ETAG guidelines..

http://www.hilti.com/holcom/modules/techlib/teli_results.jsp?type=software&subtype=anchor

That site may contain some other information too. ---
Andrew

 

[Qshake]

Hilti is, indeed, another good source for this information complete with design examples (based on my latest information booklet).

 

[JAE]

Yes...we use the HILTI data for their epoxy product (HSE 2411 I believe). It offers the various development lengths required to achieve rebar yield, ultimate, etc.

 

[Qshake]

Brandnew,

It wouldn't hurt to call the local the Hilti distributor and ask for some catalogs - you might even get a free lunch out of the deal!! Here in this area, they love to come over at lunch and talk up the new products.

 

[thaidavid]

Brandnew,
Very few contractors like to drill much more than 6" into existing concrete for epoxy dowels. Try to limit your requirements to fall within this limit, as they will love you forever if you don't make them drill too deeply.
David

 

[ishvaaag]

the site with the ETAG documents

http://www.eota.be

then go to endorsed ETAGS

it is the 001

7 pdf files

The hilti program expires in 30 days but you may ask reenactment that then is free and for life...they give you a personal PIN or serial number to use.