Existing Concrete Structure, No As Built or Existing Drawings, How to verify Capacity?

[IsaacStructural]

I've got what looks to be a series of little projects involving putting some AC panels on existing roofs. When previously discussed, the example projects had various steel bar joist roofs, wood roofs etc. Basically I'm supposed to do some quick calcs to verify the roof capacity and provide a simple letter, with an attachment detail or two, as required.

Now when we go live with a real project, the first project comes in and it has a concrete roof structure with no drawings and only some assorted close up photographs of concrete beams. I informed them I couldn't do a whole lot without some decent field information and I don't have X-Ray vision to see what the reinforcing is. Now the electrical engineer/PM on the project is giving me a hard time and saying local guys don't have a problem with this. I'm not sure if this is because they are able to go on site and field verify, or if they are just cavalier about writing letters certifying roofs they can't actually verify.

the only options I can think are:

1. to analyze the slab and beams as if they had minimum steel reinforcing and see if they would work for the loading (doubtful)
2. calculate the loads carefully and try to show that the panels represent only a small increase in total load (<5%) which might work

Anyone got any other suggestions?

Am I crazy? It is a small fee project, so any kind of destructive testing or X-Ray is probably not going to work.

Kind of want to send the electrical engineer a zoomed in photograph of some random piece of wire and ask him to send me a stamped and signed letter certifying I won't get killed if I pull on it.

Licensed Structural Engineer and Licensed Professional Engineer (Illinois)

 

[BAretired]

Equally spaced point loads produce the same bending moment as a uniform load if the number of spaces is even, slightly less if the number of spaces is odd.

BA