field review - what should I check? 14

[newlearner]

I am a structural engineer. I would like to know what should be done for field review as a professional in the concrete construction site. Any special item I should check? Comment and suggestion are appreciated very much. Thank.

 

[archeng59]

I always start the observations by walking the entire site and look at the overall condition of the structural portion of the project. Does anything look wrong compared to my mental concept of what things should look like and what the drawings show? Anything that looks "funny" gets a much closer look and comparison with the set of drawings you take with you to the site. Take another lap, or two, around the site and look at everything more closely. Again, look for things that look "funny" and not what you expect to see. Bolts missing. Holes cut thru members with a torch. Holes larger than the bolt head or nut or washer, especially in baseplates. Missing welds. Members that are not straight, plumb or level. Missing members. Member in the wrong configuration or location compared to the drawigns. Obvious field modifications to members or connections. If the contractor tries to talk alot to you while you are there, he's trying to distract you and to keep you from looking around, in my opinion. Don't talk to anyone about anything except the jobsite superintendant. You are there for the owner. Not the contractor.

 

[hokie66]

Zambo,
In a beam, a small projection might be OK. But in a flat slab or flat plate, punching shear is critical, so it is unacceptable to allow projection of the column into the slab. Punching shear capacity is directly proportional to the effective depth, and if the effective depth is decreased, that also limits the critical shear perimeter. So this is one issue on which I won't compromise in the field.

 

[BAretired]

I agree with hokie on that. Consider a 12 x 12 column supporting a 6" thick flat plate with #5 bars in the top mat and 1" cover. The average effective depth of the top mat, b_o is 6 - 1.625 = 4.375". The effective perimeter is (12 + 4.375)4 = 65.5" and b_o*d = 286.5.

If the column projects 20mm (say 3/4") above the form, b_o drops to 62.5" and b_o*d becomes 226.5.

The shear strength decreases to 79% of its value with full depth. Also, the vertical sides of the column rising into the slab tend to cause a stress riser.

Get out the cold chisel.

BA

 

[hokie66]

BA has a good point about the stress riser created by the column projection. It is neglected in pile cap design, but I think it would be another reason not to do this in flat slabs and flat plates.

 

[csd72]

Take a small copy of the drawings if possible (smaller than the original but big enough to read everything) then tick each thing of with a coloured pencil as you check it. Write comments where noted.

If you are not thorough and sequential you will miss things. I agree with the general overlook first though, sometimes you cannot see the forest for the trees.

I still have copies of my markups from years ago, they make good references.

 

[bigmig]

some of the advice on here makes me laugh. Coming from someone who spent some time laughing at all the white collars on a job, and now being a white collar I can tell you the "don't talk to anyone insignificant" attitude, "don't waste the owners money", "look angry" (I realize this is tongue in cheek) is a lot of the reason our wonderful designs get built bass akwards. You walking onto that job looking like a starched **** only confirms to everyone out there what they thought about engineers in the 1st place.

Be approachable. Encourage questions from the guys building your project. Donate your lunch hour to learning how your design can be better built the guy doing it in the field. I can guarantee this will win you more return business than you can imagine while earning you respect that will last for years.

 

[BAretired]

Be approachable! Good advice. I don't believe an engineer inspecting the work should be aloof from the men on the jobsite. And any pretense at annoyance (or any other emotion) while assessing the work is folly.

On the other hand, any attempt at hiding annoyance is equally wrong. If you come across something which is totally botched up, you must tell the superintendent in no uncertain terms to correct it before resuming further work. If it means canceling a concrete pour, do it.

BA

 

[nuche1973]

One more thing: Don't agree to anything. If the contractor tries to get you to verbally agree to changes or input on "means and methods" issue, simply reply that he needs to send you a RFI that you can review at the office.

 

[hokie66]

nuche1973,
Saying "Don't agree to anything" is too broad. An engineer should be able to make decisions on site about things he is inspecting, and if not, he has a phone. Now, if you mean real changes which require some study, I agree with you.