a. How wide must a wall footing be if the load is 9,500 pounds per foot of wall length, and the footing rests on a sandy gravel?
Show calculations and make a sketch. Assume that it is 18" thick. b. How large must a square column footing be to support a load of 65,000 pounds if it stands on silty gravel? Show calculations. Make a sketch of the footing, assuming that it is 18" thick. © Diane Reid
1 answer:
Answer:
a) 38"
b) L = 5.7'
Step-by-step explanation:
a) Given
P = 9,500 lb/ft
Thick = 18"
We assume an allowable bearing pressure of σ = 3000 lb/sf
If Stress = Force / Area
σ = P/A
Solving for area
A = P/σ ⇒ A = 9,500 lb/ft/3000 lb/sf
⇒ A = 3.167 sf, or 3.167 ft wide, per foot of length.
⇒ A = 38" wide
We can see the pic 1 in order to understand the answer.
b) Given
P = 65,000 pounds = 65,000 lb
Thick = 18" = 1.5'
We assume an allowable bearing pressure of σ = 2000 lb/sf
If Stress = Force / Area
σ = P/A
Solving for area
A = P/σ ⇒ A = 65,000 lb/2000 lb/sf
⇒ A = 32.5 sf
then A = L² ⇒ L = √A = √(32.5 sf) = 5.7 ft
Finally L = 5.7'
We can see the pic 2 in order to understand the answer.
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