Steel Pipe Grade and Strength

[Engineerrrd]

I have a project where I am re-analyzing a previous cell phone tower for additional antennas. In the previous calculations, it specifies steel pipe legs (PIPE 2.875 od x 0.203w) but calls them out at "A53 GR. B (46 ksi minimum)".

I know standard steel pipes are 35 ksi, has anyone seen 46 ksi steel pipe before? My assumption is that they had just mis-typed it in the calculations.

Please, let me know if you have seen 46ksi steel pipes before, thanks.

 

[JAE]

ASTM A53, Grade B is listed in the AISC manual as 35 ksi yield and 60 ksi tensile stress.

46 ksi doesn't sound right to me under A53 grade B.

 

[msquared48]

46 ksi is usually for steel HSS or Tube sections (A500 grade B), not pipe.

It would have to be A500 Grade C to be 46 ksi pipe.

Sounds like a typo. So, the question is then, what do you have? Bay need to take a sample and do some testing here if there is no other information.

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

 

[woodman88]

Check the calculations design values. Are they using 35 ksi or 46 ksi values for the pipe?

Garth Dreger PE
AZ Phoenix area

 

[Engineerrrd]

The design values listed are only on the front page of the report and then I only have the results of the analysis (not actual input information).

Comparing the allowable values, it seems as if they were designing for 46 ksi steel. It just confusing because the leg member size is called out as "PIPE 2.875 od x 0.203w", therefore it is not an HSS member meaning it shouldn't be 46ksi though, right?

 

[woodman88]

Sounds like you may need to have the pipes tested.
Have you seen the tower or looked at pictures of it, to see if pipes were used?
You may also want to have the pipe sizes checked. As there may have been a changed order during construction for larger size 36 ksi pipes to be used.

Garth Dreger PE
AZ Phoenix area

 

[msquared48]

Is the design company still in business which would allow you the opportunity to ask them the question?

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

 

[MikeDB]

You did not say how old the tower was. Did they have HSS when the tower was made. It is not uncommon for tower manufacturers to use a higher yield strength than standard, hopefully because they spec and receive steel at that strength level. I have seen this on several makes of towers. I assume that the steel has the higher yield strength as indicated on the original design, but I do use the newer design areas. I'm guessing that the tower would not fair very well if you check it for the 35ksi steel.

You could always have a sample tested.