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field review - what should I check?
13

field review - what should I check?

field review - what should I check?

(OP)
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.  

RE: field review - what should I check?

Check the diamater (by the way not that easy) and spacing of reinforcing. Besides that, walk around with with a clipboatd and a pissed off look on your face and pretend to write something down every few minutes.  

RE: field review - what should I check?

I often use a voice recorder... I have trouble finding a flat surface for using the clipboard.

Dik

RE: field review - what should I check?

Follow Jeds advice closely.  

Add a squint / eyebrow furl with a head cock to the side.  Hold for 5 seconds, add a few degrees, hold and release.

Watch as people look at what you just looked at.

Points of interest:
1. Required steel is there and in place
2. Spacing
3. Clearance
4. Splices
5. Size
6. Orientation
7. Construction joint locations (if specified on plans)
8. Isolation materials at walls / pipes if needed
9. Water stops if needed
10. Embedded steel for the next pour is in place
11. . . .
 

RE: field review - what should I check?

Actually, you can save yourself a lot of time if you inspect only the items which have been done incorrectly and then ignore the rest of their work, and get back to the office, and the real money making work.

In effect, this was what my first boss was saying as he bitched about me burning his profits on the job, when I took too long checking shop drawings or out on inspections.  You only ended up with 7 redlined items on those shop drawing, or you only came back with 4 items which needed fixing on this inspection trip, why didn't you check those things first and be done with it, what took you so long?  Obviously with his vast experience over mine, he was much quicker at seeing what needed red lining, or seeing clear across the construction site what needed inspecting, but that comes with time.  So, take the time and use and study aids like those suggested above.  Furthermore, you were involved in the design so you should know some of the spots that might need a little special attention.

So, give er hell, be thorough, and keep in mind that forming carpenters, iron workers and cement finishers don't know everything, or even nearly as much as they think they do.  But, you can still learn by watching them and taking an interest in what they are doing.  Why does it go together easier this way, can my design account for that in the future?
 

RE: field review - what should I check?

I always make a checklist of the things that are important.  I do this because jobsites are noisy and distracting, the superintendents are trying to intimidate you, etc.  The checklist keeps me from getting distracted and makes sure I just check the important stuff.

If the contractor is nice to me, I will give him a copy of the checklist in advance (with a lot of things added), and usually, viola - everything is fixed by the time I get there.

RE: field review - what should I check?

(OP)
Thank you very much for all comment, for the check list and for templete of Site visit report. If I have a chance to do field review, I will take your advice.

Thank JAE for providing link to "Construction Admin - Legal Responsibility". I do have some questions concerning responsibility. I will read comments there.

Your comments are appreciated very much.

RE: field review - what should I check?

Your company would have issued a specification with the design drawings. Everything that is requested in the specifications should be requested on-site. Obvious that you look at reinforcement, size, spacing, splices, cover etc. Look for any reinforcement which has been displaced for conduits, if any reinforcement has been cut to make way for a pipe, make sure extra reinforcement has been laid next to the opening.

Request concrete tests, I would ask to see 1 test result per 50 cubic metres of placed concrete.  

RE: field review - what should I check?

2
In addition to all the above, make sure the reinforcement mats are adequately supported.  Concreters are big footed oafs who will can make short work of lowering bars if they are not firmly supported.  Another stupid thing to look for is columns which are cast too high.

RE: field review - what should I check?

hokie

What are the ramifications if the columns are cast too high? I image it would affect punching shear because of the change of location of the construction joint and the flexural capacity of the slab over the support.

What are the rectifications if the columns are cast to high? Would it be as simple as jackhammering the columns down to the correct level.

Have you noticed columns poured to the incorrect level regularly in your time and how do you ensure the builder cast's the columns to the correct level?

Apologies for hijacking this thread, it is something for my own interest when performing field inspections.

RE: field review - what should I check?

Yes, that is correct, punching shear capacity is compromised because of the slick, formed projection into the slab.  Also, you can't get any bottom bars to go over the column.  And yes, I have had this happen a few times, thus my cautionary advice.  If it is caught early enough, a sawcut should be used to make the joint neat, then chip off the excess.  Unfortunately, sometimes it is only caught when the formwork, and maybe the reinforcement, is in place.  Chipping it off at that stage makes a messy joint, with likely cracking off the corners below the slab, which then require repair.

Ensuring builders do the right thing?  I think that is impossible.  Ignorance can't be eradicated.  We just have to do the best we can.  I think some builders deliberately cast columns high to aid in making neat joints.

RE: field review - what should I check?

I'm doing inspections on a job at the moment in which they regularly pour the columns 50-120mm above the forms ( 2 or 3 columns in every pour). It's become very annoying,  especially when the builder doesn't do anything about it until I point it out the day before the pour.  

Newlearner, you also need to make sure that the builders pour the columns before they pour the deck.  I prefer at least a day prior.
 

RE: field review - what should I check?

Tried to pull that one on you as well, pwht1?  Sounds like you are seeing a lot of the dumb stuff they do on site.  Unfortunately, a lot of young engineers get very limited opportunities to see how their designs are implemented.

RE: field review - what should I check?

Check to see that the contractor is working off the current set of approved plans, and the latest answers to any RFI's.

I often have had nightmares about this...

Oh, and DO NOT approve anything that is either not in place yet, as in "I was going to do that tomorrow", or that you cannot see, as in " I was going to call you, but just had to pour".   

Mike McCann
MMC Engineering
Motto:  KISS
Motivation:  Don't ask

RE: field review - what should I check?

Oh yeah Hokie, lots and lots.  Today, they dumped all the slurry they use to prime the concrete lines on the deck so it gets mixed in with the concrete.  I don't know what that'll do but it's poor workmanship.

Also NewLearner, tell the builder that you are to approve all cutting and bending of reo.  Otherwise before you know it all of your column starter bars will be cut off because they clash with a PT anchor.     

RE: field review - what should I check?

2
Pouring columns higher than the underside of the next slab is unacceptable.  It results in a peripheral shear problem.  We must make the contractor chip out the top concrete in each column until it is flush with the forms for the slab.  No other solution will suffice.

BA

RE: field review - what should I check?

Agree completely, BA.  I hope my comments weren't interpreted otherwise.

RE: field review - what should I check?

Whoops, BAretired and hokie66 I always expect the columns to be cast 20mm higher than the slab forms. The reason, as mentioned earlier is to make a neat joint. Of course if higher (say 50-120mm) of course the excess concrete would have to be chipped off as it would be impossible to correctly place the rebar.

But is 20mm higher unacceptable? I'm always ready to listen to advice.

RE: field review - what should I check?

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.

RE: field review - what should I check?

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.  

RE: field review - what should I check?

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, bo is 6 - 1.625 = 4.375". The effective perimeter is (12 + 4.375)4 = 65.5" and bo*d = 286.5.

If the column projects 20mm (say 3/4") above the form, bo drops to 62.5" and bo*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

RE: field review - what should I check?

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.

RE: field review - what should I check?

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.

RE: field review - what should I check?

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.

RE: field review - what should I check?

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

RE: field review - what should I check?

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.

RE: field review - what should I check?

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.   

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