New opening in Tilt Panel

[hawkaz]

I have a project where we are cutting some new small openings in existing tilt panels (Seismic design category D). The plan reviewer has requested "reinforcement, or metals equivalent to 2-#5 all around concrete wall opening".

Does anyone know why this might be needed? I don't need it for strength. Unfortunately, the reviewer is out of the office- and we are trying to resubmit as fast as possible

Thanks

 

[fancypants]

Look at ACI 318-08 14.3.7 basically tells you you need 2 # 5 bars around door, windows, etc...

I bet that is where he is coming from.

 

[asixth]

How can you install #5's after the fact. When cutting new openings into existing panels I have anchored a steel channel as a header and maybe for the jamb if theres not much concrete to work with.

May require fire protection.

 

[slickdeals]

When you have vertical load coming in the panel, it will act as a deep beam over the door opening.

I think the logic for the steel channel is that it acts as a tension tie.

The panel is probably designed on a per foot basis for wind loads. Once you cut the opening, you will have to account for this loss of reinforcing and what will pick up this load.

It’s no trick to get the answers when you have all the data. The trick is to get the answers when you only have half the data and half that is wrong and you don’t know which half - LORD KELVIN

 

[hawkaz]

Picking up the load is easy with strongbacks or bracing- and I completely agree with the deep beam practice.

What has anyone done the meet this minimum jamb steel requirement? Channels or steel plate is one way, but is it really acting as intended? I don't see how you can get good enough anchorage to make this function as rebar would.


To discuss theory- What is the purpose of these bars in the first place. I believe that this is probably intended for crack control at the high stress points created by openings, primarily generated during curing. If that is the sole function of this rebar- then it is basically useless and not necessary when cutting openings in existing panels. Comments?

 

[ztengguy]

Sounds like the reviewer is just a pain in the ass.

As a deep beam, check it for the next horizontal beam up, chances are, its going to work. For the out of plane wind load, you can check each leg left over in the panel, if the opening is not at the center (or location of max momemt) and you can show there is enough vertical steel remaining, chances are your going to be ok. What size opening and what width of panel do you have? For crack control you can cut circular holes at the corners, and then grout in the door, window, etc. hopefully the flashing covers the cuts. If it cracks, then the grout should crack, and not the panel.

 

[msquared48]

Just add two horizontal members between the vertical strongbacks at the interior of the wall opening, and afterset bolt the strongbacks and horizontal members to the panel in the vicinity of the window two on each side.

If the Architect complains, blame it on the reviewer.

Mike McCann
MMC Engineering

http://mmcengineering.tripod.com

 

[slickdeals]

M^2, are you talking about reinforcing the jamb with a pilaster from inside?

My understanding of a strongback is when you have a narrow jamb on one side of the opening which gets strengthened. If the panel was designed originally with no opening, there probably is no existing strongback?

It’s no trick to get the answers when you have all the data. The trick is to get the answers when you only have half the data and half that is wrong and you don’t know which half - LORD KELVIN