RCC Column Located Just Near The Boundry

Without knowing more detail, this cannot be answered. Is this an isolated column? a flag pole perhaps? does it have moment parallel to, and/or perpendicular to, the boundary?

This almost comes down to knowing the actual circumstances before determining if it is feasible.

The best bet is a strip along the boundary, but if there is moment perpendicular to the boundary, that probably won't work.

If the RC column in question is located along the perimeter foundation wall of adequate length and there are other RC columns located either side of it, it is possible to design a "GRADE BEAM" along the exterior foundation wall that'll distributed the applied design forces from the columns and the wall above. Either that, or you're going to have to design a mat foundation of sufficient breadth and thickness to safely carry the RC column in question. You'll still need a comprehensive geotechnical report to ascertain allowable soil bearing pressures and long term settlement rates and magnitudes.

Sorry, I cannot go into greater detail or make further suggestions without knowing more factors.

Better start thinking of reasonable design alternatives and do your homework. Good luck!

You could design an offset footing, but the column would be required to carry eccentric moment.

You could move the column further from the property line to permit a concentric footing. This would mean cantilevering the floors and roof beyond the column.

Perhaps it would be best if you provide a sketch of the condition you are trying to achieve. By the way, RCC in North America refers to "Roller Compacted Concrete" which I don't think is what you mean.

Please refer attached plan and typcal section of view of column,but C1, C2,C3, C4 & C5 column is adjuscent to boundary and hence no space for footong. These column are 10" x 10" size and idealy approx 3' x 3' space for footing is required. But here boundary side no space is available, that means footing vertical centre line is not matching with proposed column centre line (eccentric). My question is, how this column steel should be designed ? steel distribution and its mesh detail of eccentric column footing.

I am not sure I understand your problem, but I think you are saying: ... the columns are 10" x 10". They require a square footing of 3' x3' but that would extend beyond the boundary, i.e. beyond the property line, so it is not an acceptable solution. Can you accept a rectangular footing, say 1'-6" x 6'-0"?

You cannot determine the way the column steel should be designed until you determine the shape and size of your foundation.

I can't zoom to see the location of all your columns.

However, an economic solution, because of property line restrictions, calls for design of "Cantilever Footings". That is two separate column footings joined by a beam that preferably does not contribute to bearing area.

If this is a homework question, RC textbooks abound in examples.

Vince

Eccentrically loaded Pad foundation with tie beams is the answer. How to design it? Ok, this pad will behave like any other cantelivered structural member. Flextural Steel Design? - if you are not a structural engineer then please get a qualified structural engineer to design it for you before you go for construction. If it is a academic home work - refer to BC Punmia or any other text book on concrete design.

Can any one suggest me, if additional tie beam required below masonary work ? we have taken plinth beam at 2000mm from ground level.

Resolution of the plan and sections provided by the OP is impossibly bad. One cannot zoom in to see the details.

I'm still of the opinion that you need a raft foundation, as I have stated above in previous posting + you need to shift your perimeter columns inward and bury them inside non-bearing walls if necessary. Provide cantilevered reinforced concrete stub-outs (akin to a beam seat) to pickup and support your exterior wall and the beam that's supporting it.

Yes, if by chance you're not a Registered & Licensed Structural Engineer please hire one, as has been previously suggested by others. This type of construction cannot be guessed and fudged by a Contractor or layman. Good Day.

===signed by CaptMoosie, PE

Civil, Structural & Environmental Engineer

Change the entire foundation to:

12" x 24" grade beam with 3 - #6 Grade 60 re-bar top and bottom with #3 stirrups @12" spacing starting 6" from columns.

Compact the fill beneath the grade beam in 12" lifts to 95%.

Actually in my opinion that's just a way of "winging it" and "guess-by-God" or "cookie cutter" approach, not sound Structural Engineering. How'd you size it up BTW? YOU NEED TO KNOW THE SUPERIMPOSED LOADS FIRST & ALLOWABLE SOIL BEARING PRESSURE! I saw none of those posted, or did I miss something???

I much prefer to actually perform an analysis and design it per ACI 318 and standard reinforced concrete design theory + good engineering practice!

Yes, but I suppose you calculate the exact load of each and every column in the house and take exact soil compaction readings for each and every pad and then size each pad differently so that all the pads have the exact same load per square inch...I think not.

Or do you just take the heaviest column load and make all the pads that size...which makes them settle different amounts and makes for a lot of cracking...usually the case.

With a 'floating' grade beam foundation it doesn't matter what the column load differentials are, they are dispersed.

With the house columns on 15' centers, a 12" wide grade beam gives you 15 square feet of bearing for each column, substantially more than the original 9 square feet originally specified and enough to carry the originally designed loads.

Yes, a grade beam may be appropriate, if only it is deep enough. But I would rather stake my PE license on a properly designed raft foundation instead for this example.

Don't forget that the applied column loads will disperse at roughly a 45 degree angle downwards and outwards at each side of the column, as measured from the side face of the columns where they interdict with the top of the grade beam.

You're going to need specialize Finite Element Analysis software to appropriately analyze and design the grade beam.....this is an "Indeterminate Beam", so don't forget about differential settlements, both short term and long term, since you have varying degrees of loading and fixity from one column to the next, especially the difference in loading between the centrally located columns and the corner column. The "spring constants" will be wholly different as well and not the same. Also, there will most likely be a moderate difference in column load supporting the floor and those column(s) supporting the floor and the stairwell framing. And don't forget the roof framing loads and the spandrel beam loads at each floor and roof level!

I suggest that you run an analysis using either the grade beam or raft foundation programs as developed by Joseph E. Bowles, PE in his Reinforced Concrete Foundation Design textbook, or use a program like "gm1-32s", "ELPLA", or "GEOTEC OFFICE"...whatever you can afford and grow accustom to. There are other geotechnical/foundation/structural programs out there, but it'll cost you a bundle + there's an acclimatisation time period involved.

Also, there are several very good analysis programs written in EXCEL that are online free....you just have to Google search to locate them.

Have a great day!

===Signed CaptMoosie, NYS PE/PhD

Civil, Structural and Environmental Engineer, and former USACE Engineer

Why dont you just do a big cidh?

cidh?????? Please explain what the heck that is, okay?

Another solution, if this new building is constructed next to existing buildings (and their foundations) is to instead install H-piles groupings and concrete column caps at each column location, with a reinforced concrete grade beam to support the exterior walls above that'll span between the pile caps. Just have to ensure that the dynamic pile driving forces won't shake up the adjacent buildings.

Or you can install reinforced concrete foundation underpinning......

In my neck of the woods, the predominant soil is glacial till which is usually a stiff clay. We might use a grade beam and cast-in-place concrete piles or screw piles spaced as required to carry the load even if there were no boundary lines to worry about.

The type of soil will have a bearing on this decision, of course.

What the heck is a cidh???

http://cee.engr.ucdavis.edu/faculty/boulanger/geo_photo_album/Foundations%20-%20Deep/CIDH%20in%20Yolo/Yolo%20Main.html

ba, it looks like you and I are on the same page about this dilemma/problem, eh?

We too have lots of glacial till here in Upstate New York, and your suggestion how to handle it is "spot on" as far as I'm concerned. I've used that type of system many times.

We also have a squishy blue clay that's like toothpaste consistency, up to several hundred feet thick, like under Albany NY, the state capital city. You should have seen the thousands of HUGE H-piles that went into the ground to support the "South Mall" back in the 60's and early 70's. I was just a kid back then dreaming some day that I'd be an Architect designed equally impressive buildings...oh well, not all dreams come true. I turned up being a Civil Engineer instead, and am loving doing what I'm doing in this field!

BTW, the South Mall's proper name is now "The Nelson Rockefeller Empire State Plaza". Google search it....it'll amaze you what 6 Billion USD will by back then (with ooddles of cost overruns too)! I can't imagine what I'd cost to build now. Most likely would bankrupt the state. I'm still amazed at the architecture to this day...I thinks it's pretty kewl; stuff and sort of ageless. Other people are not of the same opinion though.....it's like modern art at the Met in NYC...some like and some don't.

Worth a trip to Albany to see it and walk through the below level Concourse or go up into the Corning Tower, the highest skyscraper in upstate NY outside NYC...a portion of the building (and the agency buildings as well) is supported at the base with post-tensioned cantilever. Pretty wild stuff! Te boss of the first engineering firm I worked for once worked for the State Office of General Services (NYSOGS) and was one of the engineers to redesign that cantilever 'cause the original design was flawed. Some pretty intense calcs involved in it's analysis and design!

Enjoy the website and have a great day up there in the Great White North (white here today as the White Ch&t is falling fast and furious....will get a foot by Midnight...oh my aching back!)

Yes, CaptMoosie, we're on the same page and I have just found out the Guest is too. A CIDH is a "Cast-in-Drilled-Hole" pile. Funny...I've been using them for years but never heard them referred to that way. Live and learn.

We're in for about six inches of snow tonight so my back will ache only half as much as yours.

Me too ba, used them for years and never heard the cidh term before. Must be a Left Coast term.....they must use them more than we do here in the NE, probably for the seismic restraints.

129, thanks for link....very nice and informative. Geezzzzz, some huge epoxy coated rebar in that construct, eh?!!!! Definitely a "back-breaker"!

Epoxy to fight the salt!

And no doubt along with the seismic concerns, FEMA probably added in a 20 foot tidal wave into the formula, lol.