PEMB spread footings
PEMB spread footings
(OP)
I'm working on the foundation design for a 130' span PEMB with 30' bay spacings. Allowable Bearing Capacity = 4 KSF. At column line A the columns are 4' above finished grade and at column line B the columns are 13' above finished grade. Bottom of footings are 5' below grade. The max. "thrust" force for such a building is 68 kips, which I received from a PEMB builder. There is an interior retaining wall 14' from column line B, which forms a trailer bay. I want to design the footings to resist the moment but the moment is so great at column line B that my footing is becoming too large. I have thought about a tie beam at the base of the footing to the retaining wall and also about using a combined footing. The combined footing also seems to turn out to be rather large.
I would appreciate any tips on how to go about reducing the footing size I currently have.
I would appreciate any tips on how to go about reducing the footing size I currently have.






RE: PEMB spread footings
RE: PEMB spread footings
RE: PEMB spread footings
I think the tie beam is the best solution. Are drilled piers an option? If so, you might could design it as more of an embedded pole-type foundation.
RE: PEMB spread footings
RE: PEMB spread footings
If not, the tie beam is obviously the best answer, but can you span it across the trailer bay? Is there a headroom issue? Or an interference issue?
DaveAtkins
RE: PEMB spread footings
I like DaveAtkins suggestion.
RE: PEMB spread footings
Drilled piers are not an option here. I'm going to talk with the PEMB manufacturer to see if the column can be extended down to grade. If this is not a possibility than I will go with the tie beam. Unfortunately, there are headroom issues in the trailer bay so I will have to keep the tie beam at the footing level. I will also have to talk with the PEMB manufacturer about allowable deflections in the pier supporting the column.
I'll post the answers I get. Thanks again!
RE: PEMB spread footings
DaveAtkins
RE: PEMB spread footings
We recently designed the foundations for a PEMB where the client wanted a dirt floor w/o tie beams. Fortunately there was was an inner wall parallel to the foundation. We tied the two together, using the conbined weight and soil between to resist sliding and overturning. The span was a little greater than yours but we were nearly at grade. Can you tie to the truck bay walls and extend them a little deeper to get the resistance that you need? If not I would look at drooping tie beams under the truck bay.