Prefab Metal Building Steel Strength

[rwpe]

I am involved in verifying the structure of an existing prefab metal building. The building was originally designed as cover structure with open walls. At some point following, walls were added and there appeared to be no retro-fit of the existing frames. For my analysis, I have hit a bump in that I am not sure as to which steel specification should be used...A36 or A572 Gr. 50? The construction period of the building is unknown, but safe to say it has been in place since the mid 1980's. It had been estimated that the building may have been constructed in the 1960's.

I would appreciate any direction as to where I might research this further.

Thanks,
Rhw

 

[jayrod12]

Barring you finding documentation indicating otherwise, I don't think you can assume it's more than A36.

 

[rwpe]

In speaking with my colleagues here locally, it was understood that the prefab industry had been using 50 ksi steel as early as the 1970's. I was hoping to see if there was some historical information as to the steel used for those building designs. I have sent the question to MMBA but have yet to receive a response.

 

[JAE]

Just have a contractor cut off several sample tabs from flanges near ends of beams where they aren't fully utilized and have a lab test them.

This of course would be limited to just those members specifically but might give you a clue on other areas of the building.

 

[TLHS]

Some may have, but it's not going to be anywhere near everyone and it's not going to be all components necessarily. It's not an assumption you're going to be able to make without documentation. Potentially just do the math with A36 steel and if it doesn't make sense then do some coupon tests if you have to.

 

[rwpe]

Thanks for your responses guys. I did receive a response from MBMA and they provided me a copy of a document, "Retrofitting/Reinforcing Metal Building Systems." It basically states that the transition to 50 ksi steel started in the 1960's and was for the most part complete by the 1980's. Also, after further research from myself and the Architect, it was determined that the building was constructed sometime between 1972 and 1981.

 

[lexpatrie]

If you aren't in too remote an area, the county property assessor could have information, usually it's online.

 

[bones206]

If you can find out the building manufacturer, that could help narrow things down. I usually can find a name plate attached on an end wall near the ridge.