Steel Tube convert to aluminum 2

[strucmar]

Hi everyone,

I am currently analyzing mullions for various projects and I'm providing steel stiffener tube. Would you please, guys help me to convert steel tube to aluminum by getting the equivalent thickness,so that I can find ways to apply it on STAAD for exact property of the mullions that I am analyzing. Thank you in advance and God Bless.

Regards,

strucmar

 

[Ron]

First determine the required "I" value in aluminum. Subtract the "I" of the supplied mullion (ok to do this since you are inserting the steel inside the mullion...if you want to be conservative, don't subtract). Then convert that remainder to steel using the ratio of Ea/Es. Then find a steel section with the necessary "I" that will fit inside the mullion.

Some storefront/curtain wall manufacturers provide steel sections to insert in their mullions. Sometimes those are not enough though and you have to improvise. I've had to slot 2 channels and a tube inside standard mullions to resist high wind loads....tight fit!

 

[MiketheEngineer]

Just adjust for change in Fb and E - should be good to go.

Rule of thumb:

AL costs three times as much as steel and might be 1/2 has strong...

 

[BAretired]

Is there a problem with dissimilar metals in contact with each other?

BA

 

[Ron]

BAretired...yes there is a problem. The steel has to be isolated by coating or wrapping.

 

[strucmar]

Ron,

I'm doing it other way around. Is it possible to multiply by 3 directly to the thickness of steel tube to convert it to aluminum according to the article I read?
Again Ron Thank you.

To others,

Thank you guys, for helping me to figure this out. Appreciate that.

 

[desertfox]

Hi strucmar

Scroll down to the heading composite beams on this link:-

http://www.roymech.co.uk/Useful_Tables/Beams/Beam_theory.html

desertfox

 

[Ron]

strucmar...now I'm confused. Are you attempting to create a composite section using aluminum and steel together? Aluminum is usually not used to strengthen a steel section...steel is usually used to strengthen an aluminum section.

Please describe your application is a bit more detail. I've used steel inside aluminum mullions, but not aluminum inside steel mullions.

If you are not compositing the sections, you don't need to go through this exercise.

Please explain.

 

[strucmar]

Desertfox,

Thank you for giving me such a reliable site. That's a big help.

Ron,

Don't be confused here ron. I'm aware that steel is stronger than aluminum and it is impossible to strengthen the steel by aluminum. My mistake regarding with my last question. The thickness that I was trying to tell you was in autocad, for able to get the equivalent value of aluminum with stiffener steel tube inside, I have to convert steel to aluminum so that I can get the properties that I need to use it in staad. My question is it is okey if I directly multiply the thickness of aluminum to 3 to convert it to steel? Thank you so much Ron.


Regards,

strucmar

 

[strucmar]

Desertfox,

Thank you for giving me such a reliable site. That's a big help.

Ron,

Don't be confused here ron. I'm aware that steel is stronger than aluminum and it is impossible to strengthen the steel by aluminum. My mistake regarding with my last question. The thickness that I was trying to tell you was in autocad, for able to get the equivalent value of aluminum with stiffener steel tube inside, I have to convert steel to aluminum so that I can get the properties that I need to use it in staad. My question is it is okey if I directly multiply the thickness of aluminum to 3 to convert it to steel? Thank you so much Ron.


Regards,

strucmar

 

[desertfox]

Hi strucmar

If your adding steel to the aluminium and not replacing it with steel, then what you have is a composite section try this link:-

http://books.google.co.uk/books?id=...ge&q=composite bars under compression&f=false

I think the short answer about multiplying by 3 is not correct.

 

[Ron]

strucmar...now I understand.

It isn't that steel is "stronger" than aluminum, it is structurally "stiffer" than aluminum (makes a difference in the deflections). For common mild steel and common structural aluminum (6063-T6 and 6061-T6), their yield strengths are somewhat similar.

To answer your question directly...yes. For your application, multiply by the ratio of Es/Ea.

 

[strucmar]

Desertfox,

Thank you for the reference. I appreciate it.

Ron,

Very well said man, Thank you for the help and hey congratulations for being most helpful.

I appreciate the time you've spent and the patience answering my questions guys.You are awesome guys, hoping to be like you someday.

Best regards,
Strucmar

 

[BAretired]

I don't believe it is correct to simply modify the wall thickness of the steel tube by the modular ratio, n = Es/Ea.

A square steel tube could be transformed to aluminum by maintaining the thickness of the top and bottom walls but by increasing the width by a factor of n. The side walls would maintain the height but increase the thickness by a factor of n. I am not sure how you would handle radiused corners using that method.

A better method is to transform the moment of inertia, that is, Ia = n*Is.

BA