Uplift of Trench footing
Uplift of Trench footing
(OP)
What is the rule of thumb for uplift regarding a trench footing? I have a 24"w X 36" deep X 40'long trench footing with 20kip of uplift & compression at the ends (from shear wall calcs). What length of the trench footing can I consider resisting uplift? I've heard that you can only consider 8' contributing to uplift resistance. The shear wall is in line with this trench footing and is not load bearing since the trusses also run parallel with the footing. The shear wall is 15'long. The wall is located in a high wind zone. Would it be prudent to analyze the footing as a beam? Any suggestions would be greatly appreciated.






RE: Uplift of Trench footing
If it is reinforced then why would you not use the whole length and figure out the soil pressure underneath from the applied loads as you would a combined footing? Then proceed to check for shear and bending.
RE: Uplift of Trench footing
DaveAtkins
RE: Uplift of Trench footing
The footing is reinforced and currently w/o any noted joints.
DaveAtkins,
If I were to analyze as a beam. Would a pin-pin condition be accurate?
RE: Uplift of Trench footing
Using just the weight of the footing, 0.6DL = 21.6 kips.
Your overturning moment = 800 kip-feet.
Therefore, e = 37' >> 40'/2.
Your footing is not big enough.
DaveAtkins
RE: Uplift of Trench footing
Need more weight, or anchors to resist the uplift.
RE: Uplift of Trench footing
The 21.6 kips is based on 0.6DL, so it already has the 1.5 FS in it.
But the footing still does not work.
DaveAtkins
RE: Uplift of Trench footing
RE: Uplift of Trench footing