Find capacity per foot & deflection of 8" high Al Channel

[tjg124]

Greetings all,

I'm an EE replacing an induction power supply (ips) in my factory, and I'm getting into the structural world (and not happy about it). But one of you could make it more fun.

I must cut a hole in a concrete block wall that will be 10 ft. wide and high enough to remove the old failing ips, and install the new ips. The roof over the old ips is modular concrete, in about 24" widths and is supported by the outside wall that I want to cut open. I am going to leave maybe 4 rows of block at the top of the wall in the area I am going to cut. The plan is to cut one row of 8" high block out from the outside to half the block's depth and install an 8" high aluminum channel, web facing flush with the outside. I must use aluminum to eliminate induced currents in the metal if it was ferrous metal. I would measure 10 ft. and extend the channel over one full block length on each end as support for the channel, remaining overhead block and roof.

After I install the first channel, we will demo the block below it to get the 10ft. wide opening, remove the old ips and then demo the back side of the block inside behind the outside aluminum channel and have a second identical aluminum channel act as additional support flush with the inside wall.

I don't have a clue how to calculate the capacity of a span of two, 8" high aluminum channels.

Any assistance provided, or reference to online data would be greatly appreciated.

Regards to all,

tjg124

 

[paddingtongreen]

You need to hire a structural engineer. The procedure you describe is dangerous.

My guess is that channels or plates, on each side of the wall, will be bolted with through bolts to the course above the cut before the cut is made. It may be necessary to chip out blocks and replace with concrete at the supports. That will depend on how much roof is supported.

This design is not a job for an amateur.

Michael.
Timing has a lot to do with the outcome of a rain dance.

 

[tjg124]

Michael,

Thanks for the response. The 24" roof panels are 12 feet long, the roof panels are 8" thick, and I intend to keep 5 courses of concrete block above the lintel.

Does that make it look better or worse?

I have contacted our local engineer here, but would appreciate your opinion.

Regards,

tjg124

 

[paddingtongreen]

Masonry tends to arch. Five courses is better than four, but not enough for arching with the width of your cut.
If your engineer cannot come up with something better, he/she could used the method I suggested, and put some aluminum lintels in, then remove the exterior plates if you wanted or just use the exterior plates.



Michael.
Timing has a lot to do with the outcome of a rain dance.

 

[RHTPE]

I would be concerned about the deflection of the aluminum channels once they begin to feel the weight of the wall and roof above - could result in cracking of the masonry above the new aluminum lintel. Knowing the properties of the aluminum channel will be essential to investigate this application - there are many different extruders out there.

I agree with the previous responses - involve a structural engineer with some experience in aluminum design.

Ralph
Structures Consulting
Northeast USA

 

[msquared48]

Depending on the situation here, I would be very concerned with the possibility of having aluminum in concact with concrete and the ensuing leaching and weakening of the concrete and aluminum. I would much prefer to see steel in this application.

Get a structural.

Mike McCann
MMC Engineering
Motto: KISS
Motivation: Don't ask

 

[tjg124]

Michael, Ralph, Mike,

Great input. Many thanks.

Rather than risk loosing energy and induction heating steel components in the wall, I may resort to a center aluminum beam support, after we remove the old ips and install the new (about 3 or 4 days total).

In your opinion, would a single aluminum center vertical support beam, splitting the lintel into two 5 foot supported spans be an aequate solution?

The aluminum I'm looking at using will be from Ryerson and is 6061-T6 - American Standard.

Regards,

Tom
tjg124

 

[engineertipsman]

Is there anyway you can use steel, and isulate it from any induction heating?

 

[tjg124]

Tipsman,

I am investigating that now with the ips manufacturer. Since the steel will potentially be as close as 1 foot away from the water cooled induction cables (room is very, very, tight), I'm guessing they will come back to me and insist on wood or aluminum. Who knows, maybe I'll build a small concrete block center pillar before I'm done!

Tom
tjg124

 

[RHTPE]

Some additional considerations:

- Is there steel reinforcing in the existing masonry (i.e. Durowall)? Probably hasn't been an issue if it does exist since the wires are small diameter (~0.146" dia).
- A precast lintel would have steel rebar in it - how does this impact the situation? Probably rules out using precast or cast-in-place.
- The precast concrete roof planks would also have steel reinforcing - I would assume this has not been a problem for the IPS.
- Ryerson supplies 2 different groups of aluminum channels - American Standard & Aluminum Association - which are you considering?


Ralph
Structures Consulting
Northeast USA

 

[IFRs]

Getting back to the original question, it is important to recognize that aluminum structures are different than steel but just as carefully designed and detailed by standard specifications and guides. The Aluminum Association publishes design guides and specifications that are similar to the AISC Specificaitons. There are as many or more 8" aluminum channels as there are steel channels. I'd go so far as to say there are more, and customized shapes are very common. In addition there are characteristics of aluminum that have only limited parallels to steel - Alloy, Temper, Hardness, etc. Aluminum is a fantastic material to work with, if you are providing a barrier between the concrete and the structure, don't write off aluminum as a choice.

 

[tjg124]

Hi Ralph,

1) Blocks are filled with vermiculite as I recall another long time engineer in the plant, telling me. No steel reinforcement.

2) News flash: I just got word back from ips supplier. He agreed to allow minimum of 6" spacing to steel. So steel is now allowed as a lintel. (Lintle?) This should solve the problem. He stated that it is possible to install sheet aluminum shielding between the high frequency cables and the steel if necessary.

3) Precast ceiling probably does contain reinforcing steel, but is now/ will be 2-3 feed from ips high frequency cables.

4) Proposed aluminum from Ryerson was American Standard.

Best regards to all and thanks for the input. Eng-tips is a teriffic resource.

Tom
tjg124

 

[paddingtongreen]

If you can have the steel six inches above the opening, you could through bolt steel channels as I suggested and still be on the first course above the opening.

Michael.
Timing has a lot to do with the outcome of a rain dance.