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RE: Who decides top of concrete level?

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I agree that sometimes it is reasonable to leave a detailed dimension up to the contractor, although I'm not sure that this situation is a good example of when to do it.  And when the contractor is being given options, it needs to be fairly clear.  I would not expect a "6-in min" dimension to have a tolerance of 30-inches unless clearly noted.  
 
But the way the RFI is worded is also important.  If the RFI simply asked "What TOC should be used at this location?", the engineer's response does not seem too unreasonable - the engineer likely just looked to see if something was noted on the drawings related to the TOC and likely didn't realize the full implications.  But if the RFI spelled out the concern with the varying depths of the steel beams and the possible alternatives in establishing the TOC, the engineer's response definitely was inadequate.
 

William C. Sherman, PE
(Bill Sherman)
CDM, Denver, CO
Phone: 303-298-1311
Fax: 303-293-8236
email: shermanwc(--nospam--at)cdm.com

 


From: Michelle Motchos [mailto:mmotchos(--nospam--at)sw-sc.com]
Sent: Friday, March 31, 2006 7:26 AM
To: seaint(--nospam--at)seaint.org
Subject: RE: Who decides top of concrete level?

To the engineer's defense:
In reality, there are some things that can be left to the discretion of the contractor.  If the 3' variation in top of pier/bottom of steel is not a "structural concern" to the EOR, the detail in question allows the General Contractor to decide whether it is easier/cheaper/faster for him to vary the pier elevations or select a constant elevation.  Same goes with the top of wall- the contractor's preferred forming system or construction sequence may dictate the preferred location or number of steps in the top of the wall.  If the engineer has considered this and is comfortable leaving it up the GC, than the notes provided are adequate.  It is then the GC's responsibility to coordinate it with what works best for him and that includes cross checking the steel and concrete shop drawings.
I have approached this situation from both ways, fully detailing or generally directing, and have seen it successful executed both ways.  The efforts of a good contractor willing to properly coordinate the construction are imperative.
 
My thoughts on a warm Friday here in the south...
 
Michelle Motchos, PE

STEVENS & WILKINSON OF SOUTH CAROLINA, INC.

Columbia, SC 

 

 


From: Padmanabhan Rajendran [mailto:rakamaka(--nospam--at)yahoo.com]
Sent: Friday, March 31, 2006 8:53 AM
To: seaint(--nospam--at)seaint.org
Subject: Re: Who decides top of concrete level?

Whoever produced the structural drawings is responsible for marking the TOC elevation on the drawings. Period. As a steel detailer, you are not responsible for it. If anyone has to worry about it, it will be the construction supervisor. You  are only responsible for producing shop detail drawings based on the structural drawings provided to you. If dimensions are missing in the structural drawings, ask for those details.

Force the engineer/architect for elevation data, if it is material for your work. As a conscientious engineer, you may want to alert the engineer/architect regarding construction problems because of the lack of elevation data on his drawings.

I suspect that the engineer/architect was the lowest bidder on the project and he did not include any money in his estimate for field survey. During detailed design phase, confronted with this issue, he might have wished away the problem by including a few stupid notes on the drawings.

Rajendran

G Vishwanath <gvshwnth(--nospam--at)yahoo.com> wrote:
Who decides top of concrete Level?

We are detailing an apartment building.
There is a floor supported on steel beams very close
to the base plate level of the columns.
Neither the bottom of base plate level nor top of
concrete level is explicitly indicated.
Instead a detail in the Structural dwg indicates the
top of concrete level as "minimum 6" below the bottom
flange of the steel beams.

This should have been easy.

Except that the beams vary in depth from a minimum of
14" to a maximum of 30"
So what do we do?
Consider the deepest of them (30") and keep the the
top of concrete level at 36" uniformly for all?
Or go hopping all over the place and have different
top of concrete levels for each case?
We sent an rfi requesting the engineer to indicate the
top of concrete levels to be considered.
The engineer answers our rfi by simply quoting the
detail that we have already seen and are not satisfied
with.

Since when is the top of concrete level being decided
by the steel detailer.
Indicating minimum 6" passes the buck to us.
How will the foundation construction be done?
Will they refer to steel dwgs?

At some other places the engineer says "keep top of
concrete at least 4" below sidewalk level. Coordinate
with Arch dwgs"

What does at least 4" mean?
Again the buck is being passed on to us?

We looked up the Arch dwgs.
An elevation of the building is shown.
The ground level varies haphazardly.
The slopes are not uniform and vary along the length
of the building.
The ground slope is also not uniform.
Are we to decide the sidewalk levels from this ?

I have misgivings about this project.
Any experiences to share?
Any opinions or advice is welcome.
Regards
Vish


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