Another pre-eng building... it's best to have the pre-eng people do the check... you may be voiding the warranty and assuming responsibility for the entire building.

Good luck getting the pre-eng building people to do that.  I've never had any luck getting any info from them, and when you ask them questions about how anything "by others" attach to their structure or is accounted for, I get the answer of "Not my problem".

An aside - I recently saw some pre-eng building plans.  The anchor bolts varied by location from 5/8" dia. to 3/4" dia., and steel sections appear to be designed for least weight.  In todays world where material costs (ie. weight of steel) aren't the controlling factors (fabrication usually controls), are pre-eng buildings past their prime??

As long as within not thin sections you have freely available a Mathcad Worksheet in the Mathcad Collaboratory site that checkes double tee tapered members for biaxial solicitation as quoted in Galambos V ed. There you may also find the method.

Respect on going the lightest it also stays the comon trend here: people even use foreign codes when the ruling parties stay unaware in order to offer economies and win the contract.

It might be due to my charming personality, but I have had very good luck getting information from metal building manufacturers regarding existing metal buildings.  

My number one problem is finding out who the manufacturer is.  It is amazing to me how Owners can spend hundreds of thousands of dollars on their buildings and throw away all the plans, specifications and shop drawings upon completion.

Once I've found out who the manufacturere is I've had no problems getting the information I need.  I've even had one manufacturer re-run the existing building calculations on the original code design and the current code design - I did have to pay for that, but it was worth it!