PEMB Foundation Design Loads

[NKT]

I am under the impression that the Pre-Engineered Metal Building (PEMB) manufacturers typically provide unfactored loads, and it is the foundation designer's responsibility to apply the appropriate load factors and combinations to design the foundation system.

One of my supervisors recently expressed the opinion that the PEMB manufacturer should provide the factored and combined loads.

I'm looking for other opinions on who should be doing the factoring and combining for PEMB foundation design, and the reasoning behind the opinions.

Thanks
-NKT

 

[JedClampett]

I hate to disagree with a supervisor, as I am one, but I'd rather get raw load data and combine them myself. There are subtleties to load combinations (uplift, 1.6 LL vs. 1.7 LL) that I'd like to interpret myself.
Plus it's much easier to verify the load quantities if they're separate.

 

[haynewp]

The PEMB mfr has given me the raw cases and the load combinations they used to design the building. They included the ASD factors on the combos since that is what they designed the building for.

I had to take the raw cases and factor for the concrete design and make any adjustments required at service level for the soil design.

My thought is that they should be able to provide you with the raw cases and combos they designed the building under, but it is your responsibility to modify as required for the foundation system design, as you stated above. You really should be getting a copy of the combos they used for the building design anyway if you are the engineer of record on the project.

 

[NKT]

Thanks JedClampett

Just to clarify, the supervisor in question is new, at a different regional office, and is more inclined toward site development work than structural. Maybe supervisor is the wrong word - he is just further up the corporate ladder than I am. His comment came as a response to a scope of work I had written for the structural portion of one of his proposals. There is no animosity involved, just a differing of opinions on this particular subject.

haynewp:
That's my line of reasoning as well. Good point on the EOR reviewing the building manufacturer's calcs.

 

[SteelPE]

I’ve seen the loads come in both factored and unfactored (service loads). I like to do my own load combinations. Sometimes we get both the factored and unfactored loads and I run my own combinations and see how they compare with the PEMB mfr factored loads. It really depends on which PEMB mfr. you are dealing with.

As a side note, sometimes we are asked to provide loads to a foundation designer or soils engineer. I always provide them the service loads because I do not want to be responsible for some obscure load case governing their design.

 

[asixth]

I have done some work will prefab electrical substations that house some serious equipment tonnage.

I always provided the foundation designer will an output summary of the reactions, this included both primary and combination load cases.

As I was using a second-order analysis to design the buildings, the combination load cases was not necessary the case of superimposing primary load cases together.

 

[oneintheeye]

unfactored loads def. then you can decide most critical load combos. Its also sometimes difficult to assess how the combos are put together, and if you feel you want to check another load case you have nothing to work from. Have recieved both, and for me, much simpler to have unfactored.