Concrete Grade Beam
Concrete Grade Beam
(OP)
I am working on engineering a house for a friend of mine and unfortunately his soil report came back suggesting that he need piles. The geotechnical report is going to give us the pile capacity and size as well as driving criteria. Now, Several questions arise.
1) do we just figure the weight of the house and divide it by the pile capacity given by the pile report to figure the number of piles required?
2) The footing (or grade beam) that spans between piles, Don't we just design like a simple concrete beam or say a beam spanning several supports? This also, I am assuming could have an effect on the number of piles required.
3) Is there a rule of thumb for figuring the weight of a house based on light frame construction?
4) Is there any other considerations to be accounted for?
Please help, thanks
Buzzer
1) do we just figure the weight of the house and divide it by the pile capacity given by the pile report to figure the number of piles required?
2) The footing (or grade beam) that spans between piles, Don't we just design like a simple concrete beam or say a beam spanning several supports? This also, I am assuming could have an effect on the number of piles required.
3) Is there a rule of thumb for figuring the weight of a house based on light frame construction?
4) Is there any other considerations to be accounted for?
Please help, thanks
Buzzer






RE: Concrete Grade Beam
Unless the house is at the edge of a swamp, elevated for flood protection, etc., it would be unusual for this type construction to require piles. If they can be used, oversized footings will almost certainly be more cost effective. A second geotechnical opinion may be worth the expense - pile driving / drilling is costly.
As for the weight of a house, see Chapter 3 in the "Residential Structural Design Guide: 2000 Edition" at this link (free .pdf download)
http://www.pathnet.org/sp.asp?id=1442
www.SlideRuleEra.net
RE: Concrete Grade Beam
Item#2: The grade beam should be designed for the loadings. If the beam is continuous, then this should be taken into account for both loads and deflections. Also consider some fixity caused by the beam at right angles.
Item#3: Yes there are... but these are generally used by house movers. Best to determine the loads on the beam.
Item#4: I'm not sure what your discipline is, but, if you are engineering a house you might want to contact a professional of that discipline.
Dik
for others: in case some turkey red flags this response, if he's engineering something, in our environs, he must be a registered engineer.
RE: Concrete Grade Beam
RE: Concrete Grade Beam
I always thought this forum was one to be used to gain knowledge or gather information that you needed. My questions were not whether anyone thought I was qualified as a licensed structural engineer.
RE: Concrete Grade Beam
RE: Concrete Grade Beam
That said, make sure you check in your local building code for any pile minimums. Sometimes there are requirements for spacing or minimum numbers of piles per cap, and so on. You will design for the reactions of the grade beam on the piles. These reactions include any dead, live, wind, snow or seismic loads and may be due to lateral as well as vertical loads. It is not just the weight of the house. You may design the grade beam as simply-supported but you will have to have steel for negative bending as well or you will get excessive cracking. You will have to then find the reactions of the grade beam as a continuous member since the reactions are higher than they would be for a simply-supported beam.
RE: Concrete Grade Beam