anchor to reinforced concrete

[Yt.]

Hi, i posted this before, but maybe this section of the forum is better place to ask for.

I need to anchor pinned supports for steel beam (by double angles) to a reinforced concrete which has a lot of rebar, according to planes i have about 4 inch betweens rebar to place the anchors. But i don't know where the rebar are placed and i have some doubts.

I don't think it'll be correct to place a second column of holes in the angles (in order to find a place to hold the anchors) because it might change the force distribution in the deformation behaviour of double angles. It will be difficult to me to asses the resistance if an anchor needs to be placed at the second column of holes.

Another idea will be to make differents angles so i can switch the angle if needed. I just have 3 beams to be supported.

I don't know nothing about melting the anchors to rebars, some guide could help.

according to your experiences, How straight rebar remains after concrete is set?

Can give me some others ideas?

 

[jayrod12]

Depending on how important it is, why not just have the concrete rebar located prior to fabrication of the angles?

 

[KootK]

One possibility:

1) fabricate a steel plate larger than your double angle connection.

2) put horizontally slotted holes in a few locations on the plate staggered so that, hopefully, the anchors can be installed successfuly.

3) if anchors cannot be installed successfully, they can site drill some new holes to make a go of it.

4) field weld your double angles to the plate.

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.

 

[Yt.]

Thanks for your answers.
Jayrod, the building already exist. I got the building plans but i think when as-built rebar position is just a reference. (A good one but not enough to my case)

KootK, that seems a good idea. What do you think about increase to much the rotation? If the anchor is placed at the side of the hole closer to the center line the extra clearance perhaps lead to an excessive rotation. I know that oversized holes aren't taken into account in the developing of codes equations for double angles, but maybe there will be some displacement that won't follow the stress distribution of an double angle (referring to the location of plastic hinges), maybe if i took a thicker plate the new stress distribution won't be so severe

 

[KootK]

You indicated that your beam supports we're to be pinned. If that's true, then more rotational flexibility is a good thing. If you need to develop plastic hinges, then my suggestion wouldn't be suitable. Neither would double angles for that matter.

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.

 

[jayrod12]

I am aware of the existing concrete condition. My point still stands. Have a structure scanning company come out, locate the rebar, draw the locations, and then you determine a layout of anchors that works.

In our office we have a little handheld rebar locator similar to the one in the picture. It does an alright job, but the companies that do this for a living have much more accurate systems.

 

[Yt.]

Hi, i'm pretty for not being able to answer your comments before. Finally we changed some of the anchorages for a different setup which also has some install time advantages and more tolerance for all connections not just supports. For the remainings anchorages i'll take my bets by locating the rebar with a locator. (sorry for not understanding your post jayrod12, English is not my native language.

Double angles equations do considerer hinges at some locations. I think that it's not necessary worst to place slotted holes at the plate, but the behaviour would be drastically changed. If we consider a yield line (not fully developed) which follows the hinges locations in a double angles it's like a V (top and front view), but the plate with slotted holes will develop something like this \_/, having a larger line than the V shaped so the yield line of the plate will consume more energy in order to develop and it should be stronger if the supposed behaviour is achieved but it has a non-typical equilibrium, because the plate may be deforming at different places when comparing with the angles. for example:

\__/
.\/ (Where the V is the double angle deformation and \__/ the plate deformation)



I'm not able to perform a proper analysis by now. So i'll try to not to guess that much
I really appreciate your comments, thanks again.